ICS 81.040.20  
 
Reference number
DRS397-4: 2023
© RSB 2023
  
 RWANDA 
STANDARD  DRS 
397-4 
 
First edition  
2023-mm-dd  
 
Use of glass in building— 
Part 4: Fire and loading  
   
DRS 397-4: 2023  
©RSB 2023- All rights reserved                  ii 
 In order to match with technological development and to keep continuous progress in industries, 
standards are subject to periodic review. Users shall ascertain that they are in possession of the latest 
edition 
 
 
 
 
 
 
 
 
© RSB 2023 
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized 
in any form or by any means, electronic or mechanical, including photocopying and microfilm, without 
prior written permission from RSB. 
Requests for permission to reproduce this document should be addressed to: 
Rwanda Standards Board 
P.O Box 7099 Kigali-Rwanda 
KK 15 Rd, 49 
Tel. +250 788303492 
Toll Free: 3250 
E-mail: info@rsb.gov.rw  
Website: www.rsb.gov.rw  
ePortal: www.portal.rsb.gov.rw  DRS 397-4: 2023 
iii                ©RSB2022- All rights reserved 
 Contents Page 
Use of glass in building — Part 4: Fire and loading ....................................................................................... 1  
1 Scope ...................................................................................................................................................... 1  
2 Normative references ............................................................................................................................ 1  
3 Terms and definitions ........................................................................................................................... 1  
4 Determination of appropriate glass thickness ................................................................................... 1  
5 Installation ............................................................................................................................................ 36  
6 Design criteria ...................................................................................................................................... 42  
7 Fire safety ............................................................................................................................................. 48  
Annex A (informative)  Procedure for calculation of the approximate deflection at centre of glass 
panel ..................................................................................................................................................... 55  
Annex B (informative)  Model calculation of glass thickness ..................................................................... 57  
Annex C (informative)  Installation of mirrors ............................................................................................... 60  
Annex D (informative)  Response reduction factor R for building systems .............................................. 63  
 DRS 397-4: 2023  
©RSB 2023- All rights reserved                  iv 
 Foreword 
Rwanda Standardsarepreparedby Technical Committees and approved by Rwanda Standards Board (RSB) 
Board of Directors in accordance with the procedures of RSB, in compliance with Annex 3 of the WTO/TBT 
agreement on the preparation, adoption and application of standards. 
The main task of technical committees is to prepare national standards. Final Draft Rwanda Standards 
adopted by technical committees are ratified by members of RSB Board of Directors for publication and 
gazettement as Rwanda Standards. 
DRS 397-4 was prepared by Technical Committee RSB/TC 9, Civil engineering and building materials.  
In the preparation of this standard, reference was made to the following standards: 
1) AS 1288, Glass in buildings – Selection and installation  
2) BS 6262, Code of practice for glazing for buildings  
3) IS 3548, Code of practice for glazing in building  
4) IS 16231-3, Use of glass in buildings — Code of practice — Part 3: Fire and loading  
The assistance derived from the above source is hereby acknowledged with thanks. 
DRS 397 consists of the following parts, under the general title Use of glass in building : 
Part 1: Terminology  
Part 2: General methodology for selection  
Part 3: Energy and light  
Part 4: Fire and loading  
Part 5: Safety related to humanimpact  
 
 
 DRS 397-4: 2023 
v                ©RSB2022- All rights reserved 
  
Committee membership  
The following organizations were represented on the Technical Committee on Civil engineering and building 
materials (RSB/TC 009) in the preparation of this standard. 
Advanced Construction Technology Services (ACTS) Rwanda 
AFRIPRECAST  
Bridge to Prosperity 
City of Kigali 
Greenpact Africa 
Mass Design Group 
Ministry of Health 
Rwanda Housing Authority (RHA) 
Rwanda Transport Development Agency (RTDA) 
Standards for Sustainability (SfS) 
University of Rwanda – College of Science and Technology (UR-CST) 
Rwanda Standards Board (RSB) – Secretariat DRS 397-4: 2023  
©RSB 2023- All rights reserved                  vi 
 Introduction 
Glazing is an important item in building construction and glass, the primary glazing element has to be selected 
to cater for several requirements. Fixing of glass is a specialized operation, when properly done, will avoid the 
hazards of broken glass. Growing trend in resorting to glazed windows/doors in buildings and structures has 
considerably increased the importance of glazing and the need for proper workmanship.  
This standard on Code of practice for use of glass in building  is envisaged to address the above concerns and 
their engineering aspects, and is brought out in various parts as listed in the foreword.  
DRS397-4 is more specifically intended to provide guidance in the design glasses for fire and loading of 
appropriate glazing for various types for building construction.  
Correct selection of materials to be used in glazing for buildings depends on many factors. Therefore, 
provisions in this part of the standard will be used in conjunction with those in other parts. This standard does 
not purport to include all the necessary provisions of a contract. Users are responsible for its correct 
application.  
Use of organic coated films including safety films on glass ( say annealed ) is not classified as safety glass as 
per this standard, and hence users have to cautiously decide on their options. 
 DRS 397-4: 2023 
1                ©RSB2022- All rights reserved 
 Use of glass in building — Part 4: Fire and loading 
1 Scope 
This Draft Rwanda Standardcoversselection and installation of glass in buildings, subject to wind loading, 
seismic loading and special considerations for fire-rated glass including its related materials.  
This standard does not cover the following:  
a) glazing system including frameless glazing system; and 
b) patent glazing. 
2 Normative references 
The following documents are referred to in the text in such a way that some or all of their content constitutes 
requirements of this document. For dated references, only the edition cited applies. For undated references, 
the latest edition of the referenced document (including any amendments) applies. 
ISO 3009, Fire-resistance tests — Elements of building construction — Glazed elements 
RS 114-2, Structural design — Part 2: Actions on structures ― Wind actions  
RS 397-1, Use of glass in building ― Part 1: Terminology  
RS 397-2, Use of glass in building ― Part 2: General methodology for selection 
3 Terms and definitions 
For the purposes of this standard, the terms and definitions given in RS 397-1 apply. 
4 Determination of appropriate glass thickness 
4.1 General 
This standard gives provisions to determine the minimum glass thickness to be used to resist the ultimate limit 
state design wind pressures. However, the location of the glass within the building requires additional 
considerations, such as safety with respect to human impact in accordance with DRS 397-5, which may 
impose either a minimum glass thickness above the basic calculation of this Part or a provision for a specific 
glass type or both.  
In addition to the provisions herein, the design requirements such as wind loads determined in accordance 
with RS 114-2 and the serviceability deflection requirement limits given in this standard shall have to be 
complied with. 
The provisions of this standard are applicable provided that the following parameters are satisfied:  DRS 397-4: 2023  
©RSB 2023- All rights reserved                  2 
 a) ultimate limit state wind pressure shall not be greater than 10.0 kPa;  
b) for laminated glass, the two sheets are of equal thickness and the interlayer material is either polyvinyl 
butyral (PVB) or an equivalent type of interlayer with a modulus of elasticity of about 24 MPa and a 
Poisson’s ratio of 0.50 at 20°C; and 
c) design flexural tensile strength of glass depends upon the design strength obtained after applying a 
factor of safety of 2.5. The minimum design strength of normal glass for thickness up to 6 mm is 16.7 
N/mm2and for thickness above 6 mm is 15.2 N/mm2. 
4.2 Design considerations 
The following design considerations shall be considered in determination of appropriate thickness of glass:  
a) the maximum area of glass panel is restricted to 15 m2;  
b) the maximum span of window is restricted to 4 m; 
c) aspect ratio of the glass panel shall be greater than 1.5. If it is less than 1.5, next higher available 
thickness shall be selected; 
d) the factor of safety used is 2.5 considering the variability in strength of glass; 
e) applicable to normal, reflective, laminated, tempered and insulating glass; 
f) applicable to rectangular panels properly secured;and 
g) design minimum thickness of laminated glass should be the maximum value of thickness in 
accordance with Table 5 of RS 397-2.  
4.3 Empirical relationship 
Empirical relation between the wind pressure, area of the glass panel and the required glass thickness can be 
used:  
𝑃𝑛𝑒𝑡𝐴= 200𝑇𝑘(𝑓𝑜𝑟 𝑇< 6 𝑚𝑚 
𝑃𝑛𝑒𝑡𝐴= 200𝑇𝑘+ 1900 ( 𝑓𝑜𝑟 𝑇> 6 𝑚𝑚 
where  
Pnet  is Net design wind pressure (N/m 2) as per 4.4; 
A  is Area of glass panel (m2); 
T  is Standard Nominal Thickness (SNT) of glass (mm) from Table 1; DRS 397-4: 2023 
3                ©RSB2022- All rights reserved 
 K  is Constant from the table 1. 
Table 1  — K value for the corresponding standard nominal thickness 
T 3 mm 4 mm 5 mm 6 mm 8 mm 10 mm 12 mm 15 mm 19 mm 25 mm 
k 1.683 1.732 1.753 1.765 1.57 1.578 1.583 1.579 1.569 1.569 
 
4.3.1 Glass supported on two opposite sides 
4.3.1.1 Normal and laminated glass panels supported on two opposite sides can be designed using 
following empirical relations:  
1) For T ≤ 6mm  
𝑏=4.39 𝑇
ට൬௉೙೐೟
௉೑൰ 
2) For T > 6mm  
𝑏=4.22 𝑇
ට൬௉೙೐೟
௉೑൰ 
4.3.1.2 Tempered/toughened panel on two opposite sides can be designed using following empirical 
relations:  
1) For T ≤ 6mm  
𝑏=3.2688 𝑇
ට൬௉೙೐೟
௉೑൰ 
2) For T ≥ 6mm  
𝑏=2.9069 𝑇
ට൬௉೙೐೟
௉೑൰ 
where  
b  is span, in m; 
𝑃௙  is strength factors as in Table 2. DRS 397-4: 2023  
©RSB 2023- All rights reserved                  4 
 4.3.1.3 For insulated glass, thickness of only one glass pane shall be considered. If the glass panes are 
of different thickness, the minimum of the two thicknesses shall be considered.  
4.3.1.4 For laminated glass, the thickness of PVB has not been considered. The value to be used is: 
 T = standard nominal thickness – thickness of PVB. 
4.4 Determination of design wind pressure 
4.4.1Net design wind pressure ( 𝑃௡௘௧) is an important parameter governing the thickness of glass to be used in 
the window panels. It depends on several factors as given below, among others: 
a) location of the building (wind zone); 
b) construction patterns around buildings (terrain category); 
c) topography of site; and 
d) building plan and height. 
4.4.2 Net design wind pressure (P net), may be defined using the following equation: 
𝑃𝑛𝑒𝑡=𝑝𝑧𝐶𝑝 
where  
Cp  isnet pressure coefficient as per RS 114-2; 
𝑝𝑧  isDesign wind pressure in N/m2 as per RS 114-2. 
𝑝𝑧= 0.6𝑉𝑧2 
𝑉𝑧=𝑉𝑏𝑘1𝑘2𝑘3 
where  
𝑉௕  is basic wind speed based on location as per RS 114-2; 
𝑘ଵ  is risk co-efficient factor as per RS 114-2; 
𝑘ଶ  terrain factor as per RS 114-2; 
𝑘ଷ  topography factor as per RS 114-2; DRS 397-4: 2023 
5                ©RSB2022- All rights reserved 
 𝑉௓  design wind speed in m/s.  
4.4.1 Laminated/Tempered/Insulating glass 
4.4.1.1 To determine the thickness of laminated/ tempered/ insulating glass, the design wind pressure 
𝑃௡௘௧is modified by dividing it with the strength or pressure factor 𝑃௙, dependent on the type of glass. The 
values of the 𝑃௙are given in table 2.  
4.4.1.2 Using the modified values of 𝑃௡௘௧, the thickness of other glass types can be obtained in 
accordance with 4.3. 
Table 2 —Strength factor p f 
S/N Glass Type 𝑷𝒇 
1. Normal (Annealed) 1.00  
2. Laminated  0.80 
3. Tempered  2.50 
4. Insulated  1.50 
5. Heat strengthened  1.60 
6. Wired glass  0.50 
4.5 Aspect Ratio ( 𝑨𝑹𝒎𝒂𝒙) 
The design of the thickness using empirical relation in accordance with 4 .3is valid up to a limiting aspect 
ratio𝐴𝑅௠௔௫. The value of 𝐴𝑅௠௔௫for different thickness (T) of glass is given in table 3 
Table 3 — Thickness and corresponding 𝑨𝑹𝒎𝒂𝒙values 
T (mm) 3 4 5 6 8 10 12 15 19 25 
𝐴𝑅𝑚𝑎𝑥 (in m2) 7.3 6.8 6.5 6.3 5.9 4.9 4.3 3.8 3.3 2.9 
4.6 Seismic design 
4.6.1 Seismic load ( EQ) 
4.6.1.1 The design for seismic forces shall be performed in steps to establish upper and lower bound 
force and movement response parameters. In addition, the response of the structure sensitive to certain 
parameters such as the damping and the stiffness of the support points may be evaluated.  
4.6.1.2 The principal design criteria for the seismic design are: 
a) the structure shall remain elastic during the design seismic event.  
b) The hangersshall stiffen the cantilever ‘tree’ structure.  DRS 397-4: 2023  
©RSB 2023- All rights reserved                  6 
 c) The hangersshall not go slack. 
4.6.2 Non-structuralelements 
Depending on response sensitivity, non-structural elements can be classified as deformation sensitive, 
acceleration sensitive, or both deformation and acceleration sensitive. Table 4 classifies non-structural 
elements according to their response sensitivity. 
Table 4 —  Response sensitivity of architectural component 
S/N Component Sensitivity 
   Acc Def 
i) Exterior skin 
a) Adhered Veneer S P 
b) Anchored Veneer S P 
c) Glass Blocks S P 
d) Prefabricated panel S P 
e) Glazing system S P 
ii) Partitions 
a) Heavy S P 
b) Light S P 
iii) Interior veneers 
 a) Stone, including marble S P 
 b) Ceramic tile S P 
iv) Parapets and appendages P - 
v) Canopies and marquees P - 
vi) Stairs P S 
Note: Acc = Acceleration sensitive; Def = Deformation sensitive; P = Primary response;S = Secondary response 
 
4.6.3 Design seismic force 
Design seismic force, 𝐹𝑝, on the non-structural element shall be calculated using the following expression as:  
𝐹𝑝=𝑍
2ቀ1+ 𝑥
ℎቁ𝑎𝑝
𝑅𝑝𝐼𝑝𝑊𝑝 
≥ 0.10𝑊௣ 
where  
𝑍 is zone factoras per Table 5; 
𝑥 is height of point of attachment of the non-structural element above the foundation; DRS 397-4: 2023 
7                ©RSB2022- All rights reserved 
 ℎ is height of the structure; 
ap  is component amplification factor as per Table 6; 
Rp   is the component response modification factor as per Table 6; 
Ip   is importance factor of the non-structural element (to be taken as 1.5); and  
Wp   is weight of the non-structural element. 
Table 5 — Seismic zone factor Z 
Seismic zone factor IV V VI VII 
Z 0.10 0.16 0.24 0.36 
 
Table 6 — Modification factors 
S/N Architectural component or element 𝒂𝒑 𝑹𝒑 
i) Interior non-structural walls and partitions: 
Plain (unreinforced) masonry walls 1.0 1.5 
All other walls and partitions 1.0 2.5 
ii) Cantilever elements (braced to structural frame above its centre of mass): 
Parapets 1.0 1.5 
Chimneys and stacks 1.0 2.5 
Exterior non-structural walls 1.0 2.5 
iii) Exterior non-structural wall elements and connections 
Wall element 1.0 2.5 
Body of wall panel connection 1.0 2.5 
Fasteners of the connecting system 1.25 1.0 
iv) Veneer 
High deformability element and attachments 1.0 2.5 
Low deformability elements and attachments 1.0 1.5 
A lower value of ap is permitted provided that a detailed dynamic analysis is performed which justifies a lower value. The value of ap 
shall not be less than 1.0. The value of ap = 1.0 is for equipment generally regarded as rigid and rigidly attached. The value of ap = 2.5 
is for flexible components or flexibly attached components.  
 
4.6.4 Seismic relative displacement 
4.6.4.1 For two connection points on the same structure A, one at a height h x, and other at a height h y, 
seismic relative displacement shall be determined as: DRS 397-4: 2023  
©RSB 2023- All rights reserved                  8 
 𝐷௣= 𝛿௫஺−𝛿௬஺ 
𝐷௣is not required to be taken as greater than 
𝑅൫ℎ௫−ℎ௬൯∆௔஺
ℎௌ௫ 
where  
𝛿௫஺  is deflection at building level x of structure A due to design seismic load determined by elastic 
analysis, and multiplied by response reduction factor (R) of the building;  
𝛿௬஺  is deflection at building level y of structure A due to design seismic load determined by elastic 
analysis, and multiplied by response reduction factor (R) of the building; 
ℎ௫  is height of level x to which upper connection point is attached; 
ℎ௬  is height of level y to which lower connection point is attached; 
∆௔஺  is allowable storey drift for structure which shall not exceed 0.004 times storey height; and 
ℎௌ௫  is storey height below level x. 
4.6.4.2 For two connection points on separate structures A and B, or separate structural systems, one at 
height, h x , and the other at a height, h y , Dp shall be determined as: 
𝐷௣= |𝛿௫஺|+ห𝛿௬஻ห 
𝐷௣is not required to be taken as greater than 
𝑅൬ℎ௫∆௔஺
ℎௌ௫+ℎ௬∆௔஻
ℎௌ௫൰ 
where  
𝛿௬஻  is deflection at building level y of structure B due to design seismic load determined by elastic 
analysis, and multiplied by response reduction factor, R, of the building as given in Annex D; 
∆௔஻  is allowable storey drift for structure B. 
4.7 Imposed loads 
The uniform distributed load and point load is to be considered based on application and is to be selected in 
accordance with 114-2. Appropriate uniform distributed load (UDL) and concentrated load are selected in 
accordance with 114-2 based on nature of building (e.g., residential, institutional, industrial building, etc.) and 
nature of activity under each building type. DRS 397-4: 2023 
9                ©RSB2022- All rights reserved 
 4.8 Load contribution 
4.8.1 Wind load 
The wind load is the effect of wind pressure which is dependent on the location, building height, topography 
and ground roughness factor. The wind speed is taken from 114-2 for the geographic location .  
4.8.2 Dead load 
In case of inclined sloped glazing, the dead weight of the glazing should be considered. In case of component 
of sloped glazing, the following corresponding component of the total glazing may be used: 
a) the point load shall be applied as a uniformly distributed load over a circular area of 0.01 m2; 
b) for a glazed panel supported on all edges, the point loading shall be applied at the centre; 
c) for free glazing edges, the point load shall be applied adjacent to the centre of the free edge; 
d) the ultimate limit state design wind pressure shall not be greater than 1.2 kPa. For greater design wind 
pressures, the glass shall be separately designed to withstand wind loading in accordance with 4.4.  
4.9 Reference chart relating wind load, maximum allowable area for a thickness of glass 
with respect to terrain category 
tables 7, 8, 9, 10, 11, 12, 13, 14 and 15 and figures 1, 2, 3, 4, 5, 6, 7, 8 and 9 below provide relationship 
between design wind pressure and maximum allowable area for a thickness of glass with respect to specific 
terrain category. User may select the type of glass depending on the support conditions. The deflection at the 
centre of glass pane can be calculated using the formula in accordance with Annex B. Typical model 
calculation to calculate and determine wind load and deflection at the centre of the glazing, is given in Annex 
B. 
Table 7 — Maximum areas (m2) for normal (annealed) glass fixed on all four sides 
Design wind pressure 
in N/Sqm Standard nominal thickness of glass 'T' in mm 
3 4 5 6 8 10 12 15 19 25 
500 2.54 4.41 6.72 9.45 14.27 15 15 15 15 15 
550 2.31 4.01 6.11 8.59 12.97 15 15 15 15 15 
600 2.12 3.68 5.6 7.88 11.89 15 15 15 15 15 
650 1.95 3.4 5.17 7.27 10.98 14.57 15 15 15 15 
700 1.82 3.15 4.8 6.75 10.19 13.53 15 15 15 15 
750 1.69 2.94  
4.48 
 6.3  
9.51 
  
12.63 
  
15 
  
15 
  
15 
 15 
800 1.59 2.76 4.2 5.91 8.92 11.84 15 15 15 15 DRS 397-4: 2023  
©RSB 2023- All rights reserved                  10 
 850 1.49 2.6 3.95 5.56 8.39 11.14 14.26 15 15 15 
900 1.41 2.45 3.73 5.25 7.93 10.52 13.46 15 15 15 
950 1,34 2.32 3.54 4.97 7.51 9.97 12.76 15 15 15 
1000 1.27 2.21 3.36 4.73 7.13 9.47 12.12 15 15 15 
1050 1.21 2.1 3.2 4.5 6.79 9.02 11.54 15 15 15 
1100 1.16 2.01 3.05 4.3 6.49 8.61 11.02 14.81 15 15 
1150 1.1 1.92 2.92 4.11 6.2 8.23 10.54 14.17 15 15 
1200 1.06 1.84 2.8 3.94 5.95 7.89 10.1 13.58 15 15 
1250 1.02 1.77 2.69 3.78 5.71 7.58 9.69 13.03 15 15 
1300 0.98 1.7 2.58 3.64 5.49 7.28 9.32 12.53 15 15 
1350 0.94 1.63 2.49 3.5 5.28 7.01 8.98 12.07 15 15 
1400 0.91 1.58 2.4 3.38 5.1 6.76 8.66 11.64 15 15 
1450 0.88 1.52 2.32 3.26 4.92 6.53 8.36 11.23 15 15 
1500 0.85 1.47 2.24 3.15 4.76 6.31 8.08 10.86 14.8 15 
1550 0.82 1.42 2.17 3.05 4.6 6.11 7.82 10.51 14.32 15 
1600 0.79 1.38 2.1 2.95 4.46 5.92 7.57 10.18 13.87 15 
1650 0.77 1.34 2.04 2.86 4.32 5.74 7.34 9.87 13.45 15 
1700 0.75 1.3 1.98 2.78 4.2 5.57 7.13 9.58 13.06 15 
1750 0.73 1.26 1.92 2.7 4.08 5.41 6.92 9.31 12.68 15 
1800 0.71 1.23 1.87 2.63 3.96 5.26 7.73 9.05 12.33 15 
1850 0.69 1.19 1.82 2.55 3.86 5.12 6.55 8.81 12 15 
1900 0.67 1.16 1.77 2.49 3.76 4.98 6.38 8.57 11.68 15 
1950 0.65 1.13 1.72 2.42 3.66 4.86 6.21 8.35 11.38 15 
2000 0.64 1.1 1.68 2.36 3.57 4.73 6.06 8.15 11.1 15 
2050 0.62 1.08 1.64 2.31 3.48 4.62 5.91 7.95 10.83 15 
2100 0.61 1,05 1.6 2.25 3.4 4.51 5.77 7.76 10.57 15 
2150 0.59 1.03 1.56 2.2 3.32 4.4 5.64 7.58 10.32 15 
2200 0.58 1 1.53 2.15 3.24 4.3 5.51 7.4 10.09 15 
2250 0.56 0.98 1.49 2.1 3.17 4.21 5.39 7.24 9.86 14.72 
2300 0.55 0.96 1.46 2.05 3.1 4.12 5.27 7.08 9.65 14.4 
2350 0.54 0.94 1.43 2.01 3.04 4.03 5.16 6.93 9.44 14.09 
2400 0.53 0.92 1.4 1.97 2.97 3.95 5.05 6.79 9.25 13.8 
2450 0.52 0.9 1.37 1.93 2.91 3.86 4.95 6.65 9.06 13.52 
2500 0.51 0.88 1.34 1.89 2.85 3.79 4.85 6.52 8.88 13.25 
2550 0.5 0.87 1.32 1.85 2.8 3.71 4.75 6.39 8.7 12.99 
2600 0.49 0.85 1.29 1.82 2.74 3.64 4.66 6.27 8.54 12.74 
2650 0.48 0.83 1.27 1.78 2.69 3.57 4.57 6.15 8.38 12.5 
2700 0.47 0.82 1.24 1.75 2.64 3.51 4.49 6.03 8.22 12.27 
2750 0.46 0.8 1.22 1.72 2.59 3.44 4.41 5.92 8.07 12.04 DRS 397-4: 2023 
11                ©RSB2022- All rights reserved 
 2800 0.45 0.79 1.2 1.69 2.55 3.38 4.33 5.82 7.93 1.83 
2850 0.45 0.77 1.18 1.66 2.5 3.32 4.25 5.72 7.79 11.62 
2900 0.44 0.76 1.16 1.63 2.46 3.27 4.18 5.62 7.65 11.42 
2950 0.43 0.75 1.14 1.6 2.42 3.21 4.11 5.52 7.52 11.23 
3000 0.42 0.74 1.12 1.58 2.35 3.16 4.04 5.43 7.4 11.04 
3050 0.42 0.72 1.1 1.55 2.34 3.1 3.97 5.34 7.28 10.86 
3100 0.41 0.71 1.08 1.52 2.3 3.05 3.91 5.26 7.16 10.68 
3150 0.4 0.7 1.07 1.5 2.26 3.01 3.85 5.17 7.05 10.51 
3200 0.4 0.69 1.05 1.48 2.23 2.96 3.79 5.09 6.94 10.35 
3250 0.39 0.68 1.03 1.45 2.2 2.91 3.73 5.01 6.83 10.19 
3300 0.39 0.67 1.02 1.43 2.16 2.87 3.67 4.94 6.73 10.04 
3350 0.38 0.66 1 1.41 2.13 2.83 3.62 4.86 6.63 9.89 
3400 0.37 0.65 0.99 1.39 2.1 2.78 3.56 4.79 6.53 9.74 
3450 0.37 0.64 0.97 1.37 2.07 2.74 3.51 4.72 6.43 9.6 
3500 0.36 0.63 0.96 1.35 2.04 2.71 3.46 4.65 6.34 9.46 
3550 0.36 0.62 0.95 1.33 2.01 2.67 3.41 4.59 6.25 9.33 
3600 0.35 0.61 0.93 1.31 1.98 2.63 3.37 4.53 6.17 9.2 
3650 0.35 0.6 0.92 1.29 1.95 2.59 3.32 4.46 6.08 9.07 
3700 0.34 0.6 0.91 1.28 1.93 2.56 3.28 4.4 6 8.95 
3750 0.34 0.59 0.9 1.26 1.9 2.53 3.23 4.34 5.92 8.83 
3800 0.33 0.58 0.88 1.24 1.88 2.49 3.19 4.29 5.84 8.72 
3850 0.33 0.57 0.87 1.23 1.85 2.46 3.15 4.23 5.76 8.6 
4000 0.32 0.55 0.84 1.18 1.78 2.37 3.03 4.07 5.55 8.28 
4050 0.31 0.54 0.83 1.17 1.76 2.34 2.99 4.02 5.48 8.18 
4100 0.31 0.54 0.82 1.15 1.74 2.31 2.96 3.97 5.41 8.08 
4150 0.31 0.53 0.81 1.14 1.72 2.28 2.92 3.93 5.35 7.98 
4200 0.3 0.53 0.8 1.13 1.7 2.25 2.89 3.88 5.28 7.89 
4250 0.3 0.52 0.79 1.11 1.68 2.23 2.85 3.83 5.22 7.79 
4300 0.3 0.51 0.78 1.1 1.66 2.2 2.82 3.79 5.16 7.7 
4350 0.29 0.51 0.77 1.09 1.64 2.18 2.79 3.74 5.1 7.61 
4400 0.29 0.5 0.76 1.07 1.62 2.15 2.72 3.66 4.99 7.44 
4450 0.29 0.5 0.76 1.06 1.6 2.13 2.72 3.66 4.99 7.44 
4500 0.28 0.49 0.75 1.05 1.59 2.1 2.69 3.62 4.93 7.36 
4550 0.28 0.49 0.74 1.04 1.57 2.08 2.66 3.58 4.88 7.28 
4600 0.28 0.48 0.73 1.03 1.55 2.06 2.66 3.58 4.83 7.2 
4650 0.27 0.47 0.72 1.02 1.53 2.04 2.61 3.5 4.77 7.12 
4700 0.27 0.47 0.71 1.01 1.52 2.01 2.58 3.47 4.72 7.05 
4750 0.27 0.46 0.71 0.99 1.5 1.99 2.55 3.43 4.67 6.97 DRS 397-4: 2023  
©RSB 2023- All rights reserved      4800 0.26 0.46 0.7
4850 0.26 0.46 0.69
4900 0.26 0.45 0.69
4950 0.26 0.45 0.68
5000 0.25 0.44 0.67
Maximum Aspect Ratio 7.3 6.8 6.5
Figure 1 — N ormal (annealed) glass fixed on all four sides
Table 8 — Maximum areas (m
Design wind 
pressure in 
N/Sqm Standard nominal thickness of glass 'T' in mm
5.38 6.38 
500 5.38 7.56 
550 4.89 6.87 
600 4.48 6.3 
650 4.14 5.82 
700 3.84 5.4 
  
             0.7 0.98 1.49 1.97 2.52 3.39 
0.69 0.97 1.47 1.95 2.5 3.36 
0.69 0.96 1.46 1.93 2.47 3.32 
0.68 0.95 1.44 1.91 2.45 3.29 
0.67 0.95 1.43 1.89 2.42 3.26 
6.5 6.3 5.9 4.9 4.3 3.8 
ormal (annealed) glass fixed on all four sides  
Maximum areas (m2) for laminated glass fixed on all four sides  
Standard nominal thickness of glass 'T' in mm  
8.38 10.38 12.38 
11.42 15 151 
10.38 13.77 15 
9.51 12.63 15 
8.78 11.65 14.91 
8.15 10.82 13.85 
 12 4.62 6.9 
4.58 6.83 
4.53 6.76 
4.48 6.69 
4.44 6.62 
3.3 2.9 
 
 
16.38 
15 
15 
15 
15 
15 
DRS 397-4: 2023 
13                ©RSB2022- All rights reserved 
 750 3.58 5.04 7.61 10.1 12.93 15 
800 3.36 4.73 7.13 9.47 12.12 15 
850 3.16 4.45 6.71 8.91 11.41 15 
900 2.99 4.2 6.34 8.42 10.77 14.48 
950 2.83 3.98 6.01 7.97 10.2 13.72 
1000 2.69 3.78 5.71 7.58 9.69 13.03 
1050 2.56 3.6 5.44 7.21 9.23 12.41 
1100 2.44 3.44 5.19 6.89 8.81 11.85 
1150 2.34 3.29 4.96 6.59 8.43 11.33 
1200 2.24 3.15 4.76 6.31 8.08 10.86 
1250 2.15 3.02 4.57 6.06 7.76 10.43 
1300 2.07 2.91 4.39 5.83 7.46 10.02 
1350 1.99 2.8 4.23 5.61 7.18 9.65 
1400 1.92 2.7 4.08 5.41 6.92 9.31 
1450 1.85 2.61 3.94 5.22 6.69 8.99 
1500 1.79 2.52 3.81 5.05 6.25 8.41 
1550 1.73 2.44 3.68 4.89 6.25 8.41 
1600 1.68 2.36 3.57 4.73 6.06 8.15 
1650 1.63 2.29 3.46 4.59 5.88 7.9 
1700 1.58 2.22 3.36 4.46 5.7 7.67 
1750 1.54 2.16 3.26 4.33 5.54 7.45 
1800 1.49 2.1 3.17 4.21 5.39 7.24 
1850 1.45 2.04 3.09 4.09 5.24 7.04 
1900 1.41 1.99 3 3.99 5.1 6.86 
1950 1.38 1.94 2.93 3.88 4.97 6.68 
2000 1.34 1.89 2.85 3.79 4.85 6.52 
2050 1.31 1.84 2.78 3.7 4.73 6.36 
2100 1.28 1.8 2.72 3.61 4.62 6.21 
2150 1.25 1.76 2.65 3.52 4.51 6.06 
2200 1.22 1.72 2.59 3.44 4.41 5.92 
2250 1.19 1.68 2.54 3.37 4.31 5.79 
2300 1.17 1.64 2.48 3.29 4.22 5.67 
2350 1.14 1.61 2.43 3.22 4.13 5.55 
2400 1.12 1.58 2.38 3.16 4.04 5.43 
2450 1.1 1.54 2.33 3.09 3.96 5.32 
2500 1.08 1.51 2.28 3.03 3.88 5.21 
2550 1.05 1.48 2.24 2.97 3.8 5.11 
2600 1.03 1.45 2.2 2.91 3.73 5.01 DRS 397-4: 2023  
©RSB 2023- All rights reserved                  14 
 2650 1.01 1.43 2.15 2.86 3.66 4.92 
2700 1 1.4 2.11 2.81 3.59 4.83 
2750 0.98 1.37 2.08 2.75 3.53 4.74 
2800 0.96 1.35 2.04 2.71 3.46 4.65 
2850 0.94 1.33 2 2.66 3.4 4.57 
2900 0.93 1.3 1.97 2.61 3.34 4.49 
2950 0.91 1.28 1.93 2.57 3.29 4.42 
3000 0.9 1.26 1.9 2.53 3.23 4.34 
3050 0.88 1.24 1.87 2.48 3.18 4.27 
3100 0.87 1.22 1.84 2.44 3.13 4.2 
3150 0.85 1.2 1.81 2.4 3.08 4.14 
3200 0.84 1.18 1.78 2.37 3.03 4.07 
3250 0.83 1.16 1.76 2.33 2.98 4.01 
3300 0.81 1.15 1.73 2.3 2.94 3.95 
3350 0.8 1.13 1.7 2.26 2.89 3.89 
3400 0.79 1.11 1.68 2.23 2.85 3.83 
3450 0.78 1.1 1.65 2.2 2.81 3.78 
3500 0.77 1.08 1.63 2.16 2.77 3.72 
3550 0.76 1.06 1.61 2.13 2.73 3.67 
3600 0.75 1.05 1.59 2.1 2.69 3.62 
3650 0.74 1.04 1.56 2.08 2.66 3.62 
3700 0.73 1.02 1.54 2.05 2.62 3.52 
3750 0.72 1.01 1.52 2.02 2.59 3.48 
3800 0.71 0.99 1.5 1.99 2.55 3.43 
3850 0.7 0.98 1.48 1.97 2.52 3.39 
3900 0.69 0.97 1.46 1.94 2.49 3.34 
3950 0.68 0.96 1.44 1.92 2.45 3.3 
4000 0.67 0.95 1.43 1.89 2.42 3.26 
4050 0.66 0.93 1.41 1.87 2.39 3.22 
4100 0.66 0.92 1.39 1.85 2.36 3.18 
4150 0.65 0.91 1.38 1.83 2.34 3.14 
4200 0.64 0.9 1.36 1.8 2.31 3.1 
4250 0.63 0.89 1.34 1.78 2.28 3.07 
4300 0.63 0.88 1.33 1.76 2.25 3.03 
4350 0.62 0.87 1.31 1.74 2.23 3 
4400 0.61 0.86 1.3 1.72 2.2 2.96 
4450 0.6 0.85 1.28 1.7 2.18 2.93 
4500 0.6 0.84 1.27 1.68 2.15 2.9 
4550 0.59 0.83 1.25 1.66 2.13 2.86 DRS 397-4: 2023 
15                ©RSB2022- All rights reserved 4600 0.58 0.82 1.24 1.65 2.11 2.83 
4650 0.58 0.81 1.23 1.63 2.08 2.8 
4700 0.57 0.8 1.21 1.61 2.06 2.77 
4750 0.57 0.8 1.2 1.59 2.04 2.74 
4800 0.56 0.79 1.19 1.58 2.02 2.72 
4850 0.55 0.78 1.19 1.58 2.02 2.72 
4900 0.55 0.77 1.16 1.55 1.98 2.66 
4950 0.54 0.76 1.14 1.52 1.94 2.61 
5000 0.54 0.76 1.14 1.52 1.94 2.61 
Maximum 
Aspect Ratio 6.5 6.2 5.7 4.8 4.3 3.6 
   
Figure 2 — Laminated glass fixed on all four sides 
Table 9 —Maximum areas (m2) for tempered glass fixed on all four sides 
Design 
wind 
pressure 
in N/Sqm Standard nominal thickness of glass 'T' in mm 
3 4 5 6 8 10 12 15 19 25 
500 6.35 11.03 15 15 15 15 15 15 15 15 
550 5.78 10.03 15 15 15 15 15 15 15 15 
600 5.29 9.2 14 15 15 15 15 15 15 15 
650 4.89 8.49 12.92 15 15 15 15 15 15 15 
700 4.54 7.88 12 15 15 15 15 15 15 15 
750 4.24 7.36 11.2 15 15 15 15 15 15 15 
DRS 397-4: 2023  
©RSB 2023- All rights reserved                  16 
 800 3.97 6.9 10.5 14.77 15 15 15 15 15 15 
850 3.74 6.49 9.88 13.9 15 15 15 15 15 15 
900 3.53 6.13 9.33 13.13 15 15 15 15 15 15 
950 3.54 5.81 8.84 12.44 15 15 15 15 15 15 
1000 3.18 5.52 8.4 11.81 15 15 15 15 15 15 
1050 3.03 5.25 8 11.25 15 15 15 15 15 15 
1100 2.89 5.02 7.64 10.74 15 15 15 15 15 15 
1150 2.76 4.8 7.3 10.27 15 15 15 15 15 15 
1200 2.65 4.6 7 9.85 14.86 15 15 15 15 15 
1250 2.54 4.41 6.72 9.45 14.27 15 15 15 15 15 
1300 2.44 4.24 6.46 9.09 13.72 14 15 15 15 15 
1350 2.35 4.09 6.22 8.75 13.21 15 15 15 15 15 
1400 2.27 3.94 6 8.44 12.74 15 15 15 15 15 
1450 2.19 3.81 5.79 8.15 12.3 15 15 15 15 15 
1500 2.12 3.68 5.6 7.88 11.89 15 15 15 15 15 
1550 2.05 3.56 5.42 7.62 11.51 15 15 15 15 15 
1600 1.99 3.45 5.25 7.38 11.15 14.8 15 15 15 15 
1650 1.93 3.34 5.09 7.16 10.81 14.35 15 15 15 15 
1700 1.87 3.25 4.94 6.95 10.49 13.92 15 15 15 15 
1750 1.82 3.15 4.8 6.75 10.19 13.53 15 15 15 15 
1800 1.76 3.07 4.67 6.56 9.91 13.15 15 15 15 15 
1850 1.72 2.98 4.54 6.39 9.64 12.8 15 15 15 15 
1900 1.67 2.9 4.42 6.22 9.39 12.46 15 15 15 15 
1950 1.63 2.83 4.31 6.06 9.15 12.14 15 15 15 15 
2000 1.59 2.76 4.2 5.91 8.92 11.84 15 15 15 15 
2050 1.55 2.69 4.1 5.76 8.7 11.55 14.78 15 15 15 
2100 1.51 2.63 4 5.63 8.49 11.27 14.43 15 15 15 
2150 1.48 2.57 3.91 5.5 8.3 11.01 14.09 15 15 15 
2200 1.44 2.51 3.82 5.37 8.11 10.76 13.77 15 15 15 
2250 1.41 2.45 3.73 5.25 7.93 10.52 7.93 15 15 15 
2300 1.38 2.4 3.65 5.14 7.75 10.29 13.17 15 15 15 
2350 1.35 2.35 3.57 5.03 7.59 10.07 12.89 15 15 15 
2400 1.32 2.3 3.5 4.92 7.43 9.86 12.62 15 15 15 
2450 1.3 2.25 3.43 4.82 7.28 9.66 12.37 15 15 15 
2500 1.27 2.21 3.36 4.73 7.13 9.47 12.12 15 15 15 
2550 1.25 2.16 3.29 4.63 6.99 9.28 11.88 15 15 15 
2600 1.22 2.12 3.23 4.54 6.86 9.1 11.65 15 15 15 
2650 1.2 2.08 3.17 4.46 6.73 8.93 11.43 15 15 15 
2700 1.18 2.04 3.11 4.38 6.61 8.77 11.22 15 15 15 DRS 397-4: 2023 
17                ©RSB2022- All rights reserved 
 2750 1.16 2.01 3.05 4.3 6.49 8.61 11.02 14.81 15 15 
2800 1.13 1.97 3 4.22 6.37 8.45 10.82 14.55 15 15 
2850 1.11 1.94 2.95 4.15 6.26 8.31 10.63 14.19 15 15 
2900 1.1 1.9 2.9 4.07 6.15 8.16 10.45 14.04 15 15 
2950 1.08 1.87 2.85 4 6.05 8.02 10.27 13.81 15 15 
3000 1.06 1.84 2.8 3.94 5.95 7.89 10.1 13.58 15 15 
3050 1.04 1.81 2.75 3.87 5.85 7.76 9.93 13.35 15 15 
3100 1.02 1.78 2.71 3.81 5.75 7.64 9.77 13.14 15 15 
3150 1.01 1.75 2.67 3.75 5.66 7.51 9.62 12.93 15 15 
3200 0.99 1.72 2.62 3.69 5.57 7.4 9.47 12.73 15 15 
3250 0.98 1.7 2.58 3.64 5.49 7.28 9.32 12.53 15 15 
3300 0.96 1.67 2.55 3.58 5.4 7.17 9.18 12.34 15 15 
3350 0.95 1.65 2.51 3.53 5.32 7.07 9.04 12.16 15 15 
3400 0.93 1.62 2.47 3.47 5.25 9.96 8.91 11.98 15 15 
3450 0.92 1.6 2.43 3.42 5.17 6.86 8.78 11.8 15 15 
3500 0.91 1.58 2.4 3.38 5.1 6.76 8.66 11.64 15 15 
3550 0.89 1.55 2.37 3.33 5.02 6.67 8.66 11.64 15 15 
3600 0.88 1.53 2.33 3.28 4.95 6.58 8.42 11.31 15 15 
3650 0.87 1.51 2.3 3.24 4.89 6.49 8.3 11.16 15 15 
3700 0.86 1.49 2.27 3.19 4.82 6.4 8.19 11.01 15 15 
3750 0.85 1.47 2.24 3.15 4.76 6.31 8.08 10.86 14.8 15 
3800 0.84 1.45 2.21 3.11 4.69 6.23 7.97 10.72 14.6 15 
3850 0.83 1.43 2.18 3.07 4.63 6.15 7.87 10.58 14.41 15 
3900 0.81 1.41 2.15 3.03 4.57 6.07 7.77 10.44 14.23 15 
3950 0.8 1.4 2.13 2.99 4.52 5.99 7.67 10.31 14.05 15 
4000 0.79 1.38 2.1 2.95 4.46 5.92 7.57 10.18 13.87 15 
4050 0.78 1.36 2.07 2.95 4.4 5.84 7.48 10.06 13.7 15 
4100 0.77 1.35 2.05 2.88 4.35 5.77 7.39 9.93 13.53 15 
4150 0.77 1.33 2.02 2.85 4.3 5.7 7.3 9.81 13.37 15 
4200 0.76 1.31 2 2.81 4.25 5.64 7.21 9.7 13.21 15 
4250 0.75 1.3 1.98 2.78 4.2 5.57 7.13 9.58 13.06 15 
4300 0.74 1.28 1.95 2.75 4.15 5.51 7.05 9.47 12.9 15 
4350 0.73 1.27 1.93 2.72 4.1 5.44 6.96 9.36 12.76 15 
4400 0.72 1.25 1.91 2.69 4.05 5.38 6.89 9.26 12.61 15 
4450 0.71 1.24 1.89 2.65 4.01 5.32 6.81 9.15 12.47 15 
4500 0.71 1.23 1.87 2.63 3.96 5.26 6.73 9.05 12.33 15 
4550 0.7 1.21 1.85 2.6 3.92 5.2 6.66 8.95 12.06 15 
4600 0.69 1.2 1.83 2.57 3.88 5.15 6.59 8.85 12.06 15 DRS 397-4: 2023  
©RSB 2023- All rights reserved                  18 4650 0.68 1.19 1.81 2.54 3.84 5.09 6.52 8.76 11.93 15 
4700 0.68 1.17 1.79 2.51 3.79 5.04 6.45 8.67 11.81 15 
4750 0.67 1.16 1.77 2.49 3.76 4.98 6.38 8.57 11.68 15 
4800 0.66 1.15 1.75 2.46 3.72 4.93 6.31 8.48 11.56 15 
4850 0.65 1.14 1.73 2.44 3.68 4.88 6.25 8.4 11.44 15 
4900 0.65 1.13 1.71 2.41 3.64 4.83 6.18 8.31 11.32 15 
4950 0.64 1.11 1.7 2.39 3.6 4.78 6.12 8.23 11.21 15 
5000 0.64 1.1 1.68 2.36 3.57 4.73 6.06 8.15 11.1 15 
Maximum 
Aspect 
Ratio 7.3 6.8 6.5 6.3 5.9 4.9 4.3 3.8 3.3 2.9 
 
Figure 3 — Tempered glass fixed on all four sides 
Table 10 — Maximum areas (m2) for insulating glass fixed on all four sides 
Design wind 
pressure in 
N/Sqm Standard nominal thickness of glass 'T' in mm 
3 + 3 4+4 5+5 6+6 8+8 10+10 12+12 
500 3.81 6.62 10.08 14.18 15 15 15 
550 3.47 6.02 9.16 12.89 15 15 15 
600 3.18 5.52 8.4 11.81 15 15 15 
650 2.93 5.09 7.75 10.91 15 15 15 
700 2.73 4.73 7.2 10.13 15 15 15 
750 2.54 4.41 6.72 9.45 14.27 15 15 
DRS 397-4: 2023 
19                ©RSB2022- All rights reserved 
 800 2.38 4.41 6.72 9.45 14.27 15 15 
850 2.24 3.89 5.93 8.34 12.59 15 15 
900 2.12 3.68 5.6 7.88 11.89 15 15 
950 2.01 3.48 5.31 7.46 11.27 14.95 15 
1000 1.91 3.31 5.04 7.09 10.7 14.2 15 
1050 1.82 3.15 4.8 6.75 10.19 13.53 15 
1100 1.73 3.01 4.58 6.44 9.73 12.91 15 
1150 1.66 2.88 4.38 6.16 9.31 12.35 15 
1200 1.59 2.76 4.2 5.91 8.92 11.84 15 
1250 1.52 2.65 4.03 5.67 8.56 11.36 14.54 
1300 1.47 2.55 3.88 5.45 8.23 10.93 13.98 
1350 1.41 2.45 3.73 5.25 7.93 10.52 13.46 
1400 1.36 2.36 3.6 5.06 7.64 10.15 12.98 
1450 1.31 2.28 3.48 4.89 7.38 9.8 12.54 
1500 1.27 2.21 3.36 4.73 7.13 9.47 12.12 
1550 1.23 2.14 3.25 4.57 6.9 9.16 11.73 
1600 1.19 2.07 3.15 4.43 6.69 8.88 11.36 
1650 1.16 2.01 3.05 4.3 6.49 8.61 11.02 
1700 1.12 1.95 2.96 4.17 6.3 8.35 10.69 
1750 1.09 1.89 2.88 4.05 6.12 8.12 10.39 
1800 1.06 1.84 2.8 3.94 5.95 7.89 10.1 
1850 1.03 1.79 2.72 3.83 5.78 7.68 9.83 
1900 1 1.74 2.65 3.73 5.63 7.48 9.57 
1950 0.98 1.7 2.58 3.64 5.49 7.28 9.32 
2000 0.95 1.66 2.52 3.54 5.35 7.1 9.09 
2050 0.93 1.61 2.46 3.46 5.22 6.93 8.87 
2100 0.91 1.58 2.4 3.38 5.1 6.76 8.66 
2150 0.89 1.54 2.34 3.3 4.98 6.61 8.45 
2200 0.87 1.5 2.29 3.22 4.86 6.46 8.26 
2250 0.85 1.47 2.24 3.15 4.76 6.31 8.08 
2300 0.83 1.44 2.19 3.08 4.65 6.18 7.9 
2350 0.81 1.41 2.14 3.02 4.55 6.04 7.74 
2400 0.79 1.38 2.1 2.95 4.46 5.92 7.57 
2450 0.78 1.35 2.06 2.89 4.37 5.8 7.42 
2500 0.76 1.32 2.02 2.84 4.28 5.68 7.27 
2550 0.75 1.3 1.98 2.78 4.2 5.57 7.13 
2600 0.73 1.27 1.94 2.73 4.12 5.46 6.99 
2650 0.72 1.25 1.9 2.67 4.04 5.36 6.86 DRS 397-4: 2023  
©RSB 2023- All rights reserved                  20 
 2700 0.71 1.23 1.87 2.63 3.96 5.16 6.73 
2750 0.69 1.2 1.83 2.58 3.89 5.16 6.61 
2800 0.68 1.18 1.8 2.53 3.82 5.07 6.49 
2850 0.67 1.16 1.77 2.49 3.76 4.98 6.38 
2900 0.66 1.14 1.74 2.44 3.69 4.9 6.27 
2950 0.65 1.12 1.71 2.4 3.63 4.81 6.16 
3000 0.64 1.1 1.68 2.36 3.57 4.73 6.06 
3050 0.62 1.09 1.65 2.32 3.51 4.66 5.96 
3100 0.61 1.07 1.63 2.29 3.45 4.58 5.86 
3150 0.61 1.05 1.6 2.25 3.4 4.51 5.77 
3200 0.6 1.03 1.57 2.22 3.4 4.44 5.68 
3250 0.59 1.02 1.55 2.18 3.29 4.37 5.59 
3300 0.58 1 1.53 2.15 3.24 4.3 5.51 
3350 0.57 0.99 1.5 2.12 3.19 4.24 5.43 
3400 0.56 0.97 1.48 2.08 3.15 4.18 5.35 
3450 0.55 0.96 1.46 2.05 3.1 4.12 5.27 
3500 0.54 0.95 1.44 2.03 3.06 4.06 5.19 
3550 0.54 0.93 1.42 2 3.01 4 5.12 
3600 0.53 0.92 1.4 1.97 2.97 3.95 5.05 
3650 0.52 0.91 1.38 1.94 2.93 3.89 4.98 
3700 0.52 0.89 1.36 1.92 2.89 3.84 4.91 
3750 0.51 0.88 1.34 1.89 2.85 3.74 4.78 
3800 0.5 0.87 1.33 1.87 2.82 3.74 4.78 
3850 0.5 0.86 1.31 1.84 2.78 3.69 4.72 
3900 0.49 0.85 1.29 1.82 2.74 3.64 4.66 
3950 0.48 0.84 1.28 1.79 2.71 3.6 4.6 
4000 0.48 0.83 1.26 1.77 2.68 3.55 4.54 
4050 0.47 0.82 1.24 1.75 2.64 3.51 4.49 
4100 0.46 0.81 1.23 1.73 2.61 3.46 4.43 
4150 0.46 0.8 1.21 1.71 2.58 3.42 4.38 
4200 0.45 0.79 1.2 1.69 2.55 3.38 4.33 
4250 0.45 0.78 1.19 1.67 2.52 3.34 4.28 
4300 0.44 0.77 1.17 1.65 2.49 3.3 4.23 
4350 0.44 0.76 1.16 2.46 3.27 3.23 4.13 
4400 0.43 0.75 1.15 1.61 2.43 3.23 4.13 
4450 0.43 0.74 1.13 1.59 2.4 3.19 4.08 
4500 0.42 0.74 1.12 1.58 2.38 3.16 4.04 
4550 0.42 0.73 1.11 1.56 2.35 3.12 4 
4600 0.41 0.7 1.1 1.54 2.33 3.09 3.95 DRS 397-4: 2023 
21                ©RSB2022- All rights reserved 4650 0.41 0.71 1.08 1.52 2.3 3.05 3.91 
4700 0.41 0.7 1.07 1.51 2.28 3.02 3.87 
4750 0.4 0.7 1.06 1.49 2.25 2.99 3.83 
4800 0.4 0.69 1.05 1.48 2.23 2.96 3.79 
4850 0.39 0.68 1.04 1.46 2.21 2.93 3.75 
4900 0.39 0.68 1.03 1.45 2.28 2.9 3.71 
4950 0.39 0.67 1.02 1.43 2.16 2.87 3.67 
5000 0.38 0.66 1.01 1.42 2.14 2.84 3.64 
Maximum 
Aspect Ratio 7.3 6.8 6.5 6.3 5.9 4.9 4.3 
 
Figure 4— Insulating glass fixed on all four sides 
 
Table 11— Maximum area (m2) for heat strengthened glass fixed on four sides 
Design 
wind 
pressure 
in N/Sqm Standard nominal thickness of glass 'T' in mm 
   
3 4 5 6 8 10 12 15 19 25 
500 4.07 7.06 10.75 15 15 15 15 15 15 15 
550 3.7 6.42 9.77 13.75 15 15 15 15 15 15 
600 3.39 5.89 8.96 12.6 15 15 15 15 15 15 
DRS 397-4: 2023  
©RSB 2023- All rights reserved                  22 
 650 3.13 5.43 8.27 11.63 15 15 15 15 15 15 
700 2.9 5.04 7.68 10.8 15 15 15 15 15 15 
750 2.71 4.71 7.17 10.08 15 15 15 15 15 15 
800 2.54 4.41 6.72 9.45 14.27 15 15 15 15 15 
850 2.39 4.15 6.32 8.9 13.43 15 15 15 15 15 
900 2.26 3.92 5.97 8.4 12.68 15 15 15 15 15 
950 2.14 3.72 5.66 7.96 12.02 15 15 15 15 15 
1000 2.03 3.53 5.38 7.56 11.42 15 15 15 15 15 
1050 1.94 3.36 5.12 7.2 10.87 14.43 15 15 15 15 
1100 1.85 3.21 4.89 6.87 10.38 13.77 15 15 15 15 
1150 1.77 3.07 4.67 6.57 9.93 13.17 15 15 15 15 
1200 1.69 2.94 4.48 6.3 9.51 12.63 15 15 15 15 
1250 1.63 2.82 4.3 6.05 9.13 12.12 15 15 15 15 
1300 1.56 2.72 4.14 5.82 8.78 11.65 14.1 15 15 15 
1350 1.51 2.62 3.98 5.6 8.46 11.22 14.36 15 15 15 
1400 1.45 2.52 3.84 5.4 8.15 10.82 13.85 15 15 15 
1450 1.4 2.44 3.71 5.21 7.87 10.45 13.37 15 15 15 
1500 1.36 2.35 3.58 5.04 7.61 10.1 12.93 15 15 15 
1550 1.31 2.28 3.47 4.88 7.36 9.77 12.51 15 15 15 
1600 1.27 2.21 3.36 4.73 7.13 9.47 12.12 15 15 15 
1650 1.23 2.14 3.26 4.58 6.92 9.18 11.75 15 15 15 
1700 1.2 2.08 3.16 4.45 6.71 8.91 11.41 15 15 15 
1750 1.16 2.02 3.07 4.32 6.52 8.66 11.08 14.89 15 15 
1800 1.13 1.96 2.99 4.2 6.34 8.42 10.77 14.48 15 15 
1850 1.1 1.91 2.91 4.09 6.17 8.19 10.48 14.09 15 15 
1900 1.07 1.86 2.83 3.98 6.01 7.97 10.2 13.72 15 15 
1950 1.04 1.81 2.76 3.88 5.85 7.77 9.94 13.37 15 15 
2000 1.02 1.77 2.69 3.78 5.71 7.58 9.69 13.03 15 15 
2050 0.99 1.72 2.62 3.69 5.57 7.39 9.46 12.71 15 15 
2100 0.97 1.68 2.56 3.6 5.44 7.21 9.23 12.41 15 15 
2150 0.95 1.64 2.5 3.52 5.31 7.05 9.02 12.12 15 15 
2200 0.92 1.61 2.44 3.44 5.19 6.89 8.81 11.85 15 15 
2250 0.9 1.57 2.39 3.36 5.07 6.73 8.62 11.58 15 15 
2300 0.88 1,54 2.34 3.29 4.96 6.59 8.43 11.33 15 15 
2350 0.87 1.5 2.29 3.22 4.86 6.45 8.25 11.09 15 15 
2400 0.85 1.47 2.24 3.15 4.76 6.31 8.08 10.86 14.8 15 
2450 0.83 1.44 2.19 3.09 4.66 6.18 7.91 10.64 14.49 15 
2500 0.81 1.41 2.15 3.02 4.57 6.06 7.76 10.43 14.2 15 
2550 0.8 1.38 2.11 2.97 4.48 5.94 7.6 10.22 13.93 15 DRS 397-4: 2023 
23                ©RSB2022- All rights reserved 
 2600 0.78 1.36 2.07 2.91 4.39 5.83 7.46 10.02 13.66 15 
2650 0.77 1.33 2.03 2.85 4.31 5.72 7.32 9.84 13.4 15 
2700 0.75 1.31 1.99 2.8 4.23 5.61 7.18 9.65 13.15 15 
2750 0.74 1.28 1.95 2.75 4.15 5.51 7.05 9.48 12.91 15 
2800 0.73 1.26 1.92 2.7 4.08 5.41 6.92 9.31 12.68 15 
2850 0.71 1.24 1.89 2.65 4.01 5.32 6.8 9.15 12.46 15 
2900 0.7 1.22 1.85 2.61 3.94 5.22 6.69 8.99 12.25 15 
2950 0.69 1.2 1.82 2.56 3.87 5.14 6.57 8.84 12.04 15 
3000 0.68 1.18 1.79 2.52 3.81 5.05 6.46 8.69 11.84 15 
3050 0.67 1.16 1.76 2.48 3.74 4.97 6.36 8.55 11.64 15 
3100 0.66 1.14 1.73 2.44 3.68 4.89 6.25 8.41 11.46 15 
3150 0.65 1.12 1.71 2.4 3.62 4.81 6.16 8.27 11.27 15 
3200 0.64 1.1 1.68 2.36 3.57 4.73 6.06 8.15 11.1 15 
3250 0.63 1.09 1.65 2.33 3.51 4.66 5.97 8.02 10.93 15 
3300 0.62 1.07 1.63 2.29 3.46 4.59 5.88 7.9 10.76 15 
3350 0.61 1.05 1.6 2.26 3.41 4.52 5.79 7.78 10.6 15 
3400 0.6 1.04 1.58 2.22 3.36 4.46 5.7 7.67 10.44 15 
3450 0.59 1.02 1.56 2.19 3.31 4.39 5.62 7.56 10.29 15 
3500 0.58 1.01 1.54 2.16 3.26 4.33 5.54 7.45 10.15 15 
3550 0.57 0.99 1.51 2.13 3.22 4.27 5.46 7.34 10 14.93 
3600 0.56 0.98 1.49 2.1 3.17 4.21 5.39 7.24 9.86 14.72 
3650 0.56 0.97 1.47 2.07 3.13 4.15 5.31 7.14 9.73 14.52 
3700 0.55 0.95 1.45 2.04 3.09 4.09 5.24 7.04 9.6 13.32 
3750 0.54 0.94 1.43 2.02 3.04 4.04 5.17 6.95 9.47 14.13 
3800 0.54 0.93 1.41 1.99 3 3.99 5.1 6.86 9.35 13.94 
3850 0.53 0.92 1.4 1.96 2.97 3.94 5.04 6.77 9.22 13.76 
3900 0.52 0.91 1.38 1.94 2.93 3.88 4.97 6.68 9.11 13.59 
3950 0.51 0.89 1.36 1.91 2.89 3.84 4.91 6.6 8.99 13.41 
4000 0.51 0.88 1.34 1.89 2.85 3.79 4.85 6.52 8.88 13.25 
4050 0.5 0.87 1.33 1.87 2.82 3.74 4.79 6.44 8.77 13.08 
4100 0.5 0.86 1.31 1.84 2.78 3.7 4.73 6.36 8.66 12.92 
4150 0.49 0.85 1.3 1.82 2.75 3.65 4.67 6.28 8.56 12.77 
4200 0.48 0.84 1.28 1.8 2.72 3.61 4.62 6.21 8.46 12.62 
4250 0.48 0.83 1.26 1.78 2.69 3.56 4.56 6.13 8.36 12.47 
4300 0.47 0.82 1.25 1.76 2.65 3.52 4.51 6.06 8.26 12.32 
4350 0.47 0.81 1.24 1.74 2.62 3.48 4.46 5.99 8.16 12.18 
4400 0.46 0.8 1.22 1.72 2.59 3.44 4.41 5.92 8.07 12.04 
4450 0.46 0.79 1.21 1.7 2.57 3.4 4.36 5.86 7.98 11.91 DRS 397-4: 2023  
©RSB 2023- All rights reserved                  24 4500 0.45 0.78 1.19 1.68 2.54 3.37 4.31 5.79 7.89 11.78 
4550 0.45 0.78 1.18 1.66 2.51 3.33 4.26 5.73 7.8 11.65 
4600 0.44 0.77 1.17 1.64 2.48 3.29 4.22 5.67 7.72 11.52 
4650 0.44 0.76 1.16 1.63 2.45 3.26 4.17 5.61 7.64 11.4 
4700 0.43 0.75 1.14 1.61 2.43 3.22 4.13 5.55 7.56 11.27 
4750 0.43 0.74 1.13 1.59 2.4 3.19 4.08 5.49 7.48 11.16 
4800 0.42 0.74 1.12 1.58 2.38 3.16 4.04 5.43 7.4 11.04 
4850 0.42 0.73 1.11 1.56 2.35 3.12 4 5.37 7.32 10.93 
4900 0.41 0.72 1.1 1.54 2.33 3.09 3.96 5.32 7.25 10.81 
4950 0.41 0.71 1.098 1.53 2.31 3.06 3.92 5.27 7.17 10.7 
5000 0.41 0.71 1.08 1.51 2.28 3.03 3.88 5.21 7.1 10.6 
Maximum 
Aspect 
Ratio 7.3 6,8 6.5 6.3 5.9 4.9 4.3 3.8 3.3 2.9 
 
Figure 5 — Heat strengthened glass fixed on four sides 
Table 12 — Maximum span (m) for normal (Annealed) glass fixed on two opposite sides 
Design 
wind 
pressure 
in 
N/Sqm Standard nominal thickness of glass 'T' in mm       
3 4 5 6 8 10 12 15 19 25 
500 0.59 0.78 0.98 1.18 1.51 1.89 2.26 2.83 3.59 4 
550 0.56 0.75 0.93 1.12 1.44 1.8 2.16 2.7 3.42 4 
600 0.54 0.72 0.89 1.07 1.38 1.72 2.07 2.58 3.27 4 
DRS 397-4: 2023 
25                ©RSB2022- All rights reserved 
 650 0.52 0.69 0.86 1.03 1.32 1.66 1.99 2.48 3.14 4 
700 0.5 0.66 0.83 0.99 1.28 1.6 1.91 2.39 3.03 3.99 
750 0.48 0.64 0.8 0.96 1.23 1.54 1.85 2.31 2.93 3.85 
800 0.46 0.62 0.77 0.93 1.19 1.49 1.79 2.24 2.83 3.73 
850 0.45 0.6 0.75 0.9 1.16 1.45 1.74 2.17 2.75 3.62 
900 0.44 0.58 0.73 0..88 1.13 1.41 1.69 2.11 2.67 3.52 
950 0.43 0.57 0.71 0.85 1.1 1.37 1.64 2.05 2.6 3.42 
1000 0.42 0.55 0.69 0.83 1.07 1.33 1.6 2 2.54 3.34 
1050 0.41 0.54 0.68 0.81 1.04 1.3 1.56 1.95 2.47 3.26 
1100 0.4 0.53 0.66 0.79 1.02 1.27 1.53 1.91 2.42 3.18 
1150 0.39 0.52 0.65 0.77 1 1.24 1.49 1.87 2.36 3.11 
1200 0.38 0.51 0.63 0.76 0.97 1.22 1.46 1.83 2.31 3.05 
1250 0.37 0.5 0.62 0.74 0.95 1.19 1.43 1.79 2.27 2.98 
1300 0.36 0.49 0.61 0.73 0.94 1.17 1.4 1.76 2.22 2.93 
1350 0.36 0.48 0.6 0.72 0.92 1.15 1.38 1.72 2.18 2.87 
1400 0.35 0.47 0.59 0.7 0.9 1.13 1.35 1.69 2.14 2.82 
1450 0.35 0.46 0.58 0.69 0.89 1.11 1.33 1.66 2.11 2.77 
1500 0.34 0.45 0.57 0.68 0.87 1.09 1.31 1.63 2.07 2.72 
1550 0.33 0.45 0.56 0.67 0.86 1.07 1.29 1.61 2.04 2.68 
1600 0.33 0.44 0.55 0.66 0.84 1.05 1.27 1.58 2 2.64 
1650 0.32 0.43 0.54 0.65 0.83 1.04 1.25 1.56 1.97 2.6 
1700 0.32 0.42 0.53 0.64 0.82 1.02 1.23 1.54 1.94 2.56 
1750 0.31 0.42 0.52 0.63 0.81 1.01 1.21 1.51 1.92 2.52 
1800 0.31 0.41 0.52 0.62 0.8 0.99 1.19 1.49 1.89 2.49 
1850 0.31 0.41 0.51 0.61 0.78 0.98 1.18 1.47 1.86 2.45 
1900 0.3 0.4 0.5 0.6 0.77 0.97 1.16 1.45 1.84 2.42 
1950 0.3 0.4 0.5 0.6 0.76 0.96 1.15 1.43 1.82 2.39 
2000 0.29 0.39 0.49 0.59 0.75 0.94 1.13 1.42 1.79 2.36 
2050 0.29 0.39 0.48 0.58 0.75 0.93 1.12 1.4 1.77 2.33 
2100 0.29 0.38 0.48 0.57 0.74 0.92 1.11 1.38 1.75 2.3 
2150 0.28 0.38 0.47 0.57 0.73 0.91 1.09 1.37 1.73 2.28 
2200 0.28 0.37 0.47 0.56 0.72 0.9 1.08 1.35 1.71 2.25 
2250 0.28 0.37 0.46 0.55 0.71 0.89 1.07 1.33 1.69 2.22 
2300 0.27 0.37 0.46 0.55 0.7 0.88 1.06 1.32 1.67 2.2 
2350 0.27 0.36 0.45 0.54 0.7 0.87 1.04 1.31 1.65 2.18 
2400 0.27 0.36 0.45 0.54 0.69 0.86 1.03 1.29 1.64 2.15 
2450 0.27 0.35 0.44 0.53 0.68 0.85 1.02 1.28 1.62 2.13 
2500 0.26 0.35 0.44 0.53 0.68 0.84 1.01 1.27 1.6 2.11 DRS 397-4: 2023  
©RSB 2023- All rights reserved                  26 
 2550 0.26 0.35 0.43 0.52 0.67 0.84 1 1.25 1.59 2.09 
2600 0.26 0.34 0.43 0.52 0.66 0.83 0.99 1.24 1.57 2.07 
2650 0.26 0.34 0.43 0.51 0.66 0.82 0.98 1.23 1.56 2.05 
2700 0.25 0.34 0.42 0.51 0.65 0.81 0.97 1.22 1.54 2.03 
2750 0.25 0.33 0.42 0.5 0.64 0.8 0.97 1.21 1.53 2.01 
2800 0.25 0.33 0.41 0.5 0.64 0.8 0.96 1.2 1.52 1.99 
2850 0.25 0.33 0.41 0.49 0.63 0.79 0.95 1.19 1.5 1.98 
2900 0.24 0.33 0.41 0.49 0.63 0.78 0.94 1.18 1.49 1.96 
2950 0.24 0.32 0.4 0.48 0.63 0.78 0.93 1.17 1.48 1.94 
3000 0.24 0.32 0.4 0.48 0.62 0.77 0.92 1.16 1.46 1.93 
3050 0.24 0.32 0.4 0.48 0.61 0.76 0.92 1.15 1.45 1.91 
3100 0.24 0.31 0.39 0.47 0.61 0.76 0.91 1.14 1.44 1.89 
3150 0.23 0.31 0.39 0.47 0.6 0.75 0.9 1.13 1.43 1.88 
3200 0.23 0.31 0.39 0.46 0.6 0.75 0.9 1.12 1.42 1.86 
3250 0.23 0.31 0.38 0.46 0.59 0.74 0.89 1.11 1.41 1.85 
3300 0.23 0.3 0.38 0.46 0.59 0.73 0.88 1.1 1.4 1.84 
3350 0.23 0.3 0.38 0.45 0.58 0.73 0.87 1.09 1.39 1.82 
3400 0.23 0.3 0.38 0.45 0.58 0.72 0.87 1.09 1.38 1.81 
3450 0.22 0.3 0.37 0.45 0.57 0.72 0.86 1.08 1.37 1.8 
3500 0.22 0.3 0.37 0.44 0.57 0.71 0.85 1.7 1.36 1.78 
3550 0.22 0.29 0.37 0.44 0.57 0.71 0.85 1.06 1.35 1.77 
3600 0.22 0.29 0.37 0.44 0.56 0.7 0.84 1.05 1.34 1.76 
3650 0.22 0.29 0.36 0.43 0.56 0.7 0.84 1.05 1.33 1.75 
3700 0.22 0.29 0.36 0.43 0.56 0.69 0.83 1.04 1.32 1.73 
3750 0.21 0.29 0.36 0.43 0.55 0.69 0.83 1.03 1.31 1.72 
3800 0.21 0.28 0.36 0.43 0.55 0.68 0.82 1.03 1.3 1.71 
3850 0.21 0.28 0.35 0.42 0.54 0.68 0.82 1.02 1.29 1.7 
3900 0.21 0.28 0.35 0.42 0.54 0.68 0.81 1.01 1.28 1.69 
3950 0.21 0.28 0.35 0.42 0.54 0.67 0.81 1.01 1.28 1.68 
4000 0.21 0.28 0.35 0.42 0.53 0.67 0.8 1 1.27 1.67 
4050 0.21 0.28 0.34 0.41 0.53 0.66 0.8 0.99 1.26 1.66 
4100 0.21 0.27 0.34 0.41 0.53 0.66 0.79 0.99 1.25 1.65 
4150 0.2 0.27 0.34 0.41 0.53 0.66 0.79 0.98 1.24 1.64 
4200 0.2 0.27 0.34 0.41 0.52 0.65 0.78 0.98 1.24 1.63 
4250 0.2 0.27 0.34 0.4 0.52 0.65 0.78 0.97 1.23 1.62 
4300 0.2 0.27 0.33 0.4 0.51 0.64 0.77 0.97 1.22 1.61 
4350 0.2 0.27 0.33 0.4 0.51 0.64 0.77 0.96 1.22 1.6 
4400 0.2 0.26 0.33 0.4 0.51 0.63 0.76 0.95 1.21 1.59 
4450 0.2 0.26 0.33 0.39 0.51 0.63 0.76 0.95 1.2 1.58 DRS 397-4: 2023 
27                ©RSB2022- All rights reserved 4500 0.2 0.26 0.33 0.39 0.5 0.63 0.75 0.94 1.2 1.57 
4550 0.19 0.26 0.32 0.39 0.5 0.63 0.75 0.94 1.19 1.56 
4600 0.19 0.26 0.32 0.39 0.5 0.62 0.75 0.93 1.18 1.56 
4650 0.19 0.26 0.32 0.39 0.5 0.62 0.74 0.93 1.18 1.55 
4700 0.19 0.26 0.32 0.38 0.49 0.62 0.74 0.92 1.17 1.54 
4750 0.19 0.25 0.32 0.38 0.49 0.61 0.73 0.92 1.16 1.53 
4800 0.19 0.25 0.32 0.38 0.49 0.61 0.73 0.91 1.16 1.52 
4850 0.19 0.25 0.31 0.38 0.48 0.61 0.73 0.91 1.15 1.51 
4900 0.19 0.25 0.31 0.38 0.48 0.6 0.72 0.9 1.15 1.51 
4950 0.19 0.25 0.31 0.37 0.48 0.6 0.72 0.9 1.14 1.5 
5000 0.19 0.25 0.31 0.37 0.48 0.6 0.72 0.9 1.13 1.49 
 
 
Figure 7 — Normal (annealed) glass fixed on two opposite sides 
Table 13 —Maximum span (m) for laminated glass fixed on two opposite sides 
Design wind 
pressure in 
N/Sqm Standard nominal thickness of glass 'T' in mm 
5.38 6.38 8.38 10.38 12.38 16.38 
500 0.88 1.05 1.35 1.69 2.03 2.53 
550 0.84 1 1.29 1.61 1.93 2.41 
600 0.8 0.96 1.23 1.54 1.85 2.31 
DRS 397-4: 2023  
©RSB 2023- All rights reserved                  28 
 650 0.77 0.92 1.18 1.48 1.78 2.22 
700 0.74 0.89 1.14 1.43 1.71 2.14 
750 0.72 0.86 1.1 1.38 1.65 2.07 
800 0.69 0.83 1.07 1.33 1.6 2 
850 0.67 0.81 1.04 1.29 1.55 1.94 
900 0.65 0.78 1.01 1.26 1.51 1.89 
950 0.64 0.76 0.98 1.22 1.47 1.84 
1000 0.62 0.74 0.95 1.19 1.43 1.79 
1050 0.6 0.73 0.93 1.16 1.4 1.75 
1100 0.59 0.71 0.91 1.14 1.37 1.71 
1150 0.58 0.69 0.89 1.11 1.34 1.67 
1200 0.57 0.68 0.87 1.09 1.31 1.63 
1250 0.55 0.66 0.85 1.07 1.28 1.6 
1300 0.54 0.65 0.84 1.05 1.26 1.57 
1350 0.53 0.64 0.82 1.03 1.23 1.54 
1400 0.52 0.63 0.81 1.01 1.21 1.51 
1450 0.51 0.62 0.79 0.99 1.19 1.49 
1500 0.51 0.61 0.78 0.97 1.17 1.46 
1550 0.5 0.6 0.77 0.97 1.15 1.44 
1600 0.49 0.59 0.75 0.94 1.13 1.42 
1650 0.48 0.58 0.74 0.93 1.12 1.39 
1700 0.48 0.57 0.73 0.92 1.1 1.37 
1750 0.47 0.56 0.72 0.9 1.08 1.35 
1800 0.46 0.55 0.71 0.89 1.07 1.33 
1850 0.46 0.55 0.7 0.88 1.05 1.32 
1900 0.45 0.54 0.69 0.87 1.04 1.3 
1950 0.44 0.53 0.68 0.85 1.03 1.28 
2000 0.44 0.53 0.68 0.84 1.01 1.27 
2050 0.43 0.52 0.67 0.83 1 1.25 
2100 0.43 0.51 0.66 0.82 0.99 1.24 
2150 0.42 0.51 0.65 0.81 0.98 1.22 
2200 0.42 0.5 0.64 0.8 0.97 1.21 
2250 0.41 0.5 0.64 0.8 0.95 1.19 
2300 0.41 0.49 0.63 0.79 0.94 1.18 
2350 0.4 0.48 0.62 0.78 0.93 1.17 
2400 0.4 0.48 0.62 0.77 0.92 1.16 
2450 0.4 0.47 0.61 0.76 0.92 1.14 
2500 0.39 0.47 0.6 0.75 0.91 1.13 
2550 0.39 0.47 0.6 0.75 0.9 1.12 DRS 397-4: 2023 
29                ©RSB2022- All rights reserved 
 2600 0.38 0.46 0.59 0.74 0.89 1.11 
2650 0.38 0.46 0.59 0.73 0.88 1.1 
2700 0.38 0.45 0.58 0.73 0.87 1.09 
2750 0.37 0.45 0.58 0.72 0.86 1.08 
2800 0.37 0.44 0.57 0.71 0.86 1.07 
2850 0.37 0.44 0.57 0.71 0.85 1.06 
2900 0.36 0.44 0.56 0.7 0.84 1.05 
2950 0.36 0.43 0.56 0.69 0.83 1.04 
3000 0.36 0.43 0.55 0.69 0.83 1.03 
3050 0.35 0.43 0.55 0.68 0.82 1.03 
3100 0.35 0.42 0.54 0.68 0.81 1.02 
3150 0.35 0.42 0.54 0.67 0.81 1.01 
3200 0.35 0.42 0.53 0.67 0.8 1 
3250 0.34 0.41 0.53 0.66 0.79 0.99 
3300 0.34 0.41 0.53 0.66 0.79 0.99 
3350 0.34 0.41 0.52 0.65 0.78 0.98 
3400 0.34 0.4 0.52 0.65 0.78 0.97 
3450 0.33 0.4 0.51 0.64 0.77 0.96 
3500 0.33 0.4 0.51 0.64 0.77 0.96 
3550 0.33 0.39 0.51 0.63 0.76 0.95 
3600 0.33 0.39 0.5 0.63 0.75 0.94 
3650 0.32 0.39 0.5 0.62 0.75 0.94 
3700 0.32 0.39 0.5 0.62 0.74 0.93 
3750 0.32 0.38 0.49 0.62 0.74 0.92 
3800 0.32 0.38 0.49 0.61 0.73 0.92 
3850 0.32 0.38 0.49 0.61 0.73 0.91 
3900 0.31 0.38 0.48 0.6 0.73 0.91 
3950 0.31 0.37 0.48 0.6 0.72 0.9 
4000 0.31 0.37 0.48 0.6 0.72 0.9 
4050 0.31 0.37 0.47 0.59 0.71 0.89 
4100 0.31 0.37 0.47 0.59 0.71 0.88 
4150 0.3 0.36 0.47 0.59 0.7 0.88 
4200 0.3 0.36 0.47 0.58 0.7 0.87 
4250 0.3 0.36 0.46 0.58 0.69 0.87 
4300 0.3 0.36 0.46 0.58 0.69 0.86 
4350 0.3 0.36 0.36 0.57 0.69 0.86 
4400 0.3 0.35 0.46 0.57 0.68 0.85 
4450 0.29 0.35 0.45 0.57 0.68 0.85 DRS 397-4: 2023  
©RSB 2023- All rights reserved                  30 4500 0.29 0.35 0.45 0.56 0.68 0.85 
4550 0.29 0.35 0.45 0.56 0.67 0.84 
4600 0.29 0.35 0.45 0.56 0.67 0.83 
4650 0.29 0.34 0.44 0.55 0.66 0.83 
4700 0.29 0.34 0.44 0.55 0.66 0.83 
4750 0.28 0.34 0.44 0.55 0.66 0.82 
4800 0.28 0.34 0.44 0.54 0.65 0.81 
4850 0.28 0.34 0.43 0.54 0.65 0.81 
4900 0.28 0.34 0.43 0.54 0.65 0.81 
4950 0.28 0.33 0.43 0.54 0.64 0.8 
5000 0.28 0.33 0.43 0.53 0.64 0.8 
 
Figure7 — Laminated glass fixed on two opposite Sides 
Table 14 — Maximum span (m) for tempered glass fixed on two opposite sides 
Design 
wind 
pressure 
in 
N/Sqm Standard nominal thickness of glass 'T' in mm 
3 4 5 6 8 10 12 15 19 25 
500 0.69 0.92 1.16 1.39 1.84 2.3 2.76 3.45 4 4 
550 0.66 0.88 1.1 1.32 1.75 2.19 2.63 3.29 4 4 
600 0.63 0.84 1.05 1.27 1.68 2.1 2.52 3.15 3.99 4 
650 0.61 0.81 1.01 1.22 1.61 2.02 2.42 3.02 3.83 4 
DRS 397-4: 2023 
31                ©RSB2022- All rights reserved 
 700 0.59 0.78 0.98 1.17 1.55 1.94 2.33 2.91 3.69 4 
750 0.57 0.75 0.94 1.13 1.5 1.88 2.25 2.81 3.57 4 
800 0.55 0.73 0.91 1.1 1.45 1.82 2.18 2.73 3.45 4 
850 0.53 0.71 0.89 1.06 1.41 1.76 2.12 2.64 3.35 4 
900 0.52 0.69 0.86 1.03 1.37 1.71 2.06 2.57 3.25 4 
950 0.5 0.67 0.84 1.01 1.33 1.67 2 2.5 3.17 4 
1000 0.49 0.65 0.82 0.98 1.3 1.63 1.95 2.44 3.09 4 
1050 0.48 0.64 0.8 0.96 1.27 1.59 1.9 2.38 3.01 3.96 
1100 0.47 0.62 0.78 0.94 1.24 1.55 1.86 2.32 2.94 3.87 
1150 0.46 0.61 0.76 0.91 1.21 1.52 1.82 2.27 2.88 3.79 
1200 0.45 0.6 0.75 0.9 1.19 1.48 1.78 2.23 2.82 3.71 
1250 0.44 0.58 0.73 0.88 1.16 1.45 1.74 2.18 2.76 3.63 
1300 0.43 0.57 0.72 0.86 1.14 1.43 1.71 2.14 2.71 3.56 
1350 0.42 0.56 0.7 0.84 1.12 1.4 1.68 2.1 2.66 3.5 
1400 0.41 0.55 0.69 0.83 1.1 1.37 1.65 2.06 2.61 3.43 
1450 0.41 0.54 0.68 0.81 1.08 1.35 1.62 2.02 2.56 3.37 
1500 0.4 0.53 0.67 0.8 1.06 1.33 1.59 1.99 2.52 3.32 
1550 0.39 0.53 0.66 0.79 1.04 1.31 1.57 1.96 2.48 3.26 
1600 0.39 0.52 0.65 0.78 1.03 1.28 1.54 1.93 2.44 3.21 
1650 0.38 0.51 0.64 0.76 1.01 1.27 1.52 1.9 2.4 3.16 
1700 0.38 0.5 0.63 0.75 1 1.25 1.5 1.87 2.37 3.12 
1750 0.37 0.49 0.62 0.74 0.98 1.23 1.47 1.84 2.33 3.07 
1800 0.37 0.49 0.61 0.73 0.97 1.21 1.45 1.82 2.3 3.03 
1850 0.36 0.48 0.6 0.72 0.96 1.19 1.43 1.79 2.27 2.99 
1900 0.36 0.47 0.59 0.71 0.94 1.18 1.41 1.77 2.24 2.95 
1950 0.35 0.47 0.59 0.7 0.93 1.16 1.4 1.75 2.21 2.91 
2000 0 .35 0.46 0.58 0.69 0.92 1.15 1.38 1.72 2.18 2.87 
2050 0.34 0.46 0.57 0.68 0.91 1.13 1.36 1.7 2.16 2.84 
2100 0.34 0.45 0.56 0.68 0.9 1.12 1.35 1.68 2.13 2.8 
2150 0.33 0.45 0.56 0.67 0.89 1.11 1.33 1.66 2.11 2.77 
2200 0.33 0.44 0.55 0.66 0.88 1.1 1.31 1.64 2.08 2,74 
2250 0.33 0.44 0.54 0.65 0.87 1.08 1.3 1.63 2.06 2.71 
2300 0.32 0.43 0.54 0.65 0.86 1.07 1.29 1.61 2.04 2.68 
2350 0.32 0.43 0.53 0.61 0.85 1.06 1.27 1.59 2.01 2.65 
2400 0.32 0.42 0.53 0.63 0.84 1.05 1.26 1.57 1.99 2.62 
2450 0.31 0.42 0.52 0.63 0.83 1.04 1.25 1.56 1.97 2.6 
2500 0.31 0.41 0.52 0.62 0.82 1.03 1.23 1.54 1.95 2.57 
2550 0.31 0.41 0.51 0.61 0.81 1.02 1.22 1.53 1.93 2.54 DRS 397-4: 2023  
©RSB 2023- All rights reserved                  32 
 2600 0.3 0.41 0.51 0.61 0.81 1.01 1.21 1.51 1.91 2.52 
2650 0.3 0.4 0.5 0.6 0.8 1 1.2 1.5 1.9 2.5 
2700 0.3 0.4 0.5 0.6 0.79 0.99 1.19 1.48 1.88 2.47 
2750 0.3 0.39 0.49 0.59 0.78 0.98 1.18 1.47 1.86 2.45 
2800 0.29 0.39 0.49 0.59 0.78 0.97 1.17 1.46 1.85 2.43 
2850 0.29 0.39 0.48 0.58 0.77 0.96 1.16 1.44 1.83 2.41 
2900 0.29 0.38 0.48 0.58 0.76 0.95 1.15 1.43 1.81 2.39 
2950 0.29 0.38 0.48 0.57 0.76 0.95 1.14 1.42 1.8 2.37 
3000 0.28 0.38 0.47 0.57 0.75 0.94 1.13 1.41 1.78 2.35 
3050 0.28 0.37 0.47 0.56 0.74 0.93 1.12 1.4 1.77 2.33 
3100 0.28 0.37 0.46 0.56 0.74 0.92 1.11 1.38 1.75 2.31 
3150 0.28 0.37 0.46 0.55 0.73 0.92 1.1 1.37 1.74 2.29 
3200 0.27 0.37 0.46 0.55 0.73 0.91 1.09 1.36 1.73 2.27 
3250 0.27 0.36 0.45 0.54 0.72 0.9 1.08 1.35 1.71 2.25 
3300 0.27 0.36 0.45 0.54 0.72 0.89 1.07 1.34 1.7 2.24 
3350 0.27 0.36 0.45 0.54 0.71 0.89 1.07 1.33 1.69 2.22 
3400 0.27 0.35 0.44 0.53 0.71 0.88 1.06 1.32 1.67 2.2 
3450 0.26 0.35 0.44 0.53 0.7 0.87 1.05 1.31 1.66 2.19 
3500 0.26 0.35 0.44 0.52 0.69 0.87 1.04 1.3 1.65 2.17 
3550 0.26 0.35 0.43 0.52 0.69 0.86 1.03 1.29 1.64 2.16 
3600 0.26 0.34 0.43 0.52 0.69 0.86 1.03 1.28 1.63 2.14 
3650 0.26 0.34 0.43 0.51 0.68 0.85 1.02 1.28 1.62 2.13 
3700 0.25 0.34 0.42 0.51 0.68 0.84 1.01 1.27 1.61 2.11 
3750 0.25 0.34 0.42 0.51 0.67 0.84 1.01 1.26 1.59 2.1 
3800 0.25 0.34 0.42 0.5 0.67 0.83 1 1.25 1.58 2.08 
3850 0.25 0.33 0.42 0.5 0.66 0.83 99 1.24 1.57 2.07 
3900 0.25 0.33 0.41 0.5 0.66 0.82 0.99 1.23 1.56 2.06 
3950 0.25 0.33 0.41 0.49 0.65 0.82 0.98 1.23 1.55 2.04 
4000 0.25 0.33 0.41 0.49 0.65 0.81 0.98 1.22 1.54 2.03 
4050 0.24 0.32 0.41 0.49 0.65 0.81 0.97 1.21 1.53 2.02 
4100 0.24 0.32 0.4 0.48 0.64 0.8 0.96 1.2 1.52 2.01 
4150 0.24 0.32 0.4 0.48 0.64 0.8 0.96 1.2 1.52 1.99 
4200 0.24 0.32 0.4 0.48 0.63 0.79 0.95 1.19 1.51 1.98 
4250 0.24 0.32 0.4 0.48 0.63 0.79 0.95 1.18 1.5 1.97 
4300 0.24 0.32 0.39 0.47 0.63 0.78 0.94 1.18 1.49 1.96 
4350 0.24 0.31 0.39 0.47 0.62 0.78 0.93 1.17 1.48 1.95 
4400 0.23 0.31 0.39 0.47 0.62 0.77 0.93 1.16 1.47 1.94 
4450 0.23 0.31 0.39 0.46 0.62 0.77 0.92 1.16 1.46 1.93 
4500 0.23 0.31 0.39 0.46 0.61 0.77 0.92 1.15 1.46 1.92 DRS 397-4: 2023 
33                ©RSB2022- All rights reserved 4550 0.23 0.31 0.38 0.46 0.61 0.76 0.91 1.14 1.45 1.9 
4600 0.23 0.3 0.38 0.46 0.61 0.76 0.91 1.14 1.44 1.89 
4650 0.23 0.3 0.38 0.45 0.6 0.75 0.9 1.13 1.43 1.88 
4700 0.23 0.3 0.38 0.45 0.6 0.75 0.9 1.12 1.42 1.87 
4750 0.22 0.3 0.37 0.45 0.6 0.75 0.89 1.12 1.42 1.86 
4800 0.22 0.3 0.37 0.45 0.59 0.74 0.89 1.11 1.41 1.85 
4850 0.22 0.3 0.37 0.45 0.59 0.74 0.89 1.11 1.4 1.84 
4900 0.22 0.3 0.37 0.44 0.59 0.73 0.88 1.1 1.39 1.84 
4950 0.22 0.29 0.37 0.44 0.58 0.73 0.88 1.1 1.39 1.83 
5000 0.22 0.39 0.37 0.44 0.58 0.73 0.87 1.09 1.38 1.82 
 
Figure 8 — Tempered glass fixed on two opposite sides 
Table 15 — Maximum span (m) for heat strengthened glass fixed on two opposite sides 
Design 
wind 
pressure 
in 
N/Sqm Standard nominal thickness of glass 'T' in mm 
    
3 4 5 6 8 10 12 15 19 25 
500 0.74 0.99 1.24 1.49 1.91 2.39 2.86 3.58 4.54 5.97 
550 0.71 0.94 1.18 1.42 1.82 2.28 2.73 3.41 4.32 5.69 
600 0.68 0.9 1.13 1.36 1.74 2.18 2.62 3.27 4.14 5.45 
650 0.65 0.87 1.09 1.3 1.67 2.09 2.52 3.14 3.98 5.23 
DRS 397-4: 2023  
©RSB 2023- All rights reserved                  34 
 700 0.63 0.84 1.05 1.26 1.61 2.02 2.42 3.03 3.83 5.04 
750 0.61 0.81 1.01 1.21 1.56 1.95 2.34 2.92 3.7 4.87 
800 0.59 0.78 0.98 1.18 1.51 1.89 2.26 2.83 3.59 4.72 
850 0.57 0.76 0.95 1.14 1.46 1.83 2.2 2.75 3.48 4.58 
900 0.55 0.74 0.92 1.11 1.42 1.78 2.14 2.67 3.38 4.45 
950 0.54 0.72 0.9 1.08 1.39 1.73 2.08 2.6 3.29 4.33 
1000 0.53 0.7 0.88 1.05 1.35 1.69 2.03 2.53 3.21 4.22 
1050 0.51 0.68 0.85 1.03 1.32 1.65 1.98 2.47 3.13 4.12 
1100 0.5 0.67 0.84 1 1.29 1.61 1.93 2.41 3.06 4.02 
1150 0.49 0.65 0.82 0.98 1.26 1.57 1.89 2.36 2.99 3.94 
1200 0.48 0.64 0.8 0.96 1.23 1.54 1.85 2.31 2.93 3.85 
1250 0.47 0.63 0.78 0.94 1.21 1.51 1.81 2.26 2.87 3.77 
1300 0.46 0.61 0.77 0.92 1.18 1.48 1.78 2.22 2.81 3.7 
1350 0.45 0.6 0.75 0.9 1.16 1.45 1.74 2.18 2.76   
1400 0.44 0.59 0.74 0.89 1.14 1.43 1.71 2.14 2.71 3.57 
1450 0.44 0.58 0.73 0.87 1.12 1.4 1.68 2.1 2.66 3.5 
1500 0.43 0.57 0.72 0.86 1.1 1.38 1.65 2.07 2.62 3.45 
1550 0.42 0.56 0.7 0.84 1.08 1.36 1.63 2.03 2.58 3.39 
1600 0.42 0.55 0.69 0.83 1.07 1.33 1.6 2 2.54 3.34 
1650 0.41 0.55 0.68 0.82 1.05 1.31 1.58 1.97 2.5 3.29 
1700 0.4 0.54 0.67 0.81 1.04 1.29 1.55 1.94 2.46 3.24 
1750 0.4 0.53 0.66 0.79 1.02 1.28 1.53 1.91 2.42 3.19 
1800 0.39 0.52 0.65 0.78 1.01 1.26 1.51 1.89 2.39 3.15 
1850 0.39 0.52 0.64 0.77 0.99 1.24 1.49 1.86 2.36 3.1 
1900 0.38 0.51 0.64 0.76 0.98 1.22 1.47 1.84 2.33 3.06 
1950 0.38 0.5 0.63 0.75 0.97 1.21 1.45 1.81 2.3 3.02 
2000 0.37 0.5 0.62 0.74 0.95 1.19 1.43 1.79 2.27 2.98 
2050 0.37 0.49 0.61 0.73 0.94 1.18 1.41 1.77 2.24 2.95 
2100 0.36 0.48 0.6 0.73 0.93 1.16 1.4 1.75 2.21 2.91 
2150 0.36 0.48 0.6 0.72 0.92 1.15 1.38 1.73 2.19 2.88 
2200 0.35 0.47 0.59 0.71 0.91 1.14 1.37 1.71 2.16 2.85 
2250 0.35 0.47 0.58 0.7 0.9 1.13 1.35 1.69 2.14 2.81 
2300 0.35 0.46 0.58 0.69 0.89 1.11 1.34 1.67 2.11 2.78 
2350 0.34 0.46 0.57 0.69 0.88 1.1 1.32 1.65 2.09 2.75 
2400 0.34 0.45 0.57 0.68 0.87 1.09 1.31 1.63 2.07 2.72 
2450 0.34 0.45 0.56 0.67 0.86 1.08 1.29 1.62 2.05 2.7 
2500 0.33 0.44 0.55 0.66 0.85 1.07 1.28 1.6 2.03 2.67 
2550 0.33 0.44 0.55 0.66 0.85 1.06 1.27 1.59 2.01 2.64 
2600 0.33 0.43 0.54 0.65 0.84 1.05 1.26 1.57 1.99 2.62 DRS 397-4: 2023 
35                ©RSB2022- All rights reserved 
 2650 0.32 0.43 0.54 0.65 0.83 1.04 1.24 1.56 1.97 2.59 
2700 0.32 0.43 0.54 0.65 0.82 1.03 1.23 1.54 1.95 2.57 
2750 0.32 0.42 0.53 0.63 0.81 1.02 1.22 1.53 1.93 2.54 
2800 0.31 0.42 0.52 0.63 0.81 1.01 1.21 1.51 1.92 2.52 
2850 0.31 0.42 0.52 0.62 0.8 1 1.2 1.5 1.9 2.5 
2900 0.31 0.41 0.51 0.62 0.79 0.99 1.19 1.49 1.88 2.48 
2950 0.31 0.41 0.51 0.61 0.79 0.98 1.18 1.47 1.87 2.46 
3000 0.3 0.4 0.51 0.61 0.78 0.97 1.17 1.46 1.85 2.44 
3050 0.3 0.4 0.5 0.6 0.77 0.97 1.16 1.45 1.84 2.42 
3100 0.3 0.4 0.5 0.6 0.77 0.96 1.15 1.44 1.82 2.4 
3150 0.3 0.39 0.49 0.59 0.76 0.95 1.14 1.43 1.81 2.38 
3200 0.29 0.39 0.49 0.59 0.75 0.94 1.13 1.42 1.79 2.36 
3250 0.29 0.39 0.49 0.58 0.75 0.94 1.12 1.4 1.78 2.34 
3300 0.29 0.39 0.48 0.58 0.74 0.93 1.12 1.39 1.77 2.32 
3350 0.29 0.38 0.48 0.57 0.74 0.92 1.11 1.38 1.75 2.31 
3400 0.29 0.38 0.48 0.57 0.73 0.92 1.1 1.37 1.74 2.29 
3450 0.28 0.38 0.47 0.57 0.73 0.91 1.09 1.36 1.73 2.27 
3500 0.28 0.37 0.47 0.56 0.72 0.9 1.08 1.35 1.71 2.26 
3550 0.28 0.37 0.46 0.56 0.72 0.9 1.08 1.34 1.7 2.24 
3600 0.28 0.37 0.46 0.55 0.71 0.89 1.07 1.33 1.69 2.22 
3650 0.28 0.37 0.46 0.55 0.71 0.88 1.06 1.33 1.68 2.21 
3700 0.27 0.36 0.46 0.55 0.7 0.88 1.05 1.32 1.67 2.19 
3750 0.27 0.36 0.45 0.54 0.7 0.87 1.05 1.31 1.66 2.18 
3800 0.27 0.36 0.45 0.54 0.69 0.87 1.04 1.3 1.65 2.16 
3850 0.27 0.36 0.45 0.54 0.69 0.86 1.03 1.29 1.63 2.15 
3900 0.27 0.35 0.44 0.53 0.68 0.85 1.03 1.28 1.62 2.14 
3950 0.26 0.35 0.44 0.53 0.68 0.85 1.02 1.27 1.61 2.12 
4000 0.26 0.35 0.44 0.53 0.68 0.84 1.01 1.27 1.6 2.11 
4050 0.26 0.35 0.44 0.52 0.67 0.84 1.01 1.26 1.59 2.1 
4100 0.26 0.35 0.43 0.52 0.67 0.83 1 1.25 1.58 2.08 
4150 0.26 0.34 0.43 0.52 0.6 0.83 0.99 1.24 1.57 2.07 
4200 0.26 0.34 0.43 0.51 0.66 0.82 0.99 1.24 1.56 2.06 
4250 0.25 0.34 0.42 0.51 0.66 0.82 0.98 1.23 1.56 2.05 
4300 0.25 0.34 0.42 0.51 0.65 0.81 0.98 1.22 1.55 2.04 
4350 0.25 0.34 0.42 0.5 0.65 0.81 0.97 1.21 1.54 2.02 
4400 0.25 0.33 0.42 0.5 0.64 0.8 0.97 1.21 1.53 2.01 
4450 0.25 0.33 0.42 0.5 0.64 0.8 0.96 1.2 1.52 2 
4500 0.25 0.33 0.41 0.5 0.64 0.8 0.95 1.19 1.51 1.99 DRS 397-4: 2023  
©RSB 2023- All rights reserved                  36 4550 0.25 0.33 0.41 0.49 0.63 0.79 0.95 1.19 1.5 1.98 
4600 0.25 0.33 0.41 0.49 0.63 0.79 0.94 1.18 1.5 1.97 
4650 0.24 0.32 0.42 0.49 0.63 0.78 0.94 1.17 1.49 1.96 
4700 0.24 0.32 0.4 0.48 0.62 0.78 0.93 1.17 1.48 1.95 
4750 0.24 0.32 0.4 0.48 0.62 0.77 0.93 1.16 1.47 1.94 
4800 0.24 0.32 0.4 0.48 0.62 0.77 0.92 1.16 1.46 1.93 
4850 0.24 0.32 0.4 0.48 0.61 0.77 0.92 1.15 1.46 1.92 
4900 0.24 0.32 0.4 0.47 0.61 0.76 0.92 1.14 1.45 1.91 
4950 0.24 0.31 0.39 0.47 0.61 0.76 0.91 1.14 1.44 1.9 
5000 0.24 0.31 0.39 0.47 0.6 0.75 0.91 1.13 1.43 1.89 
 
Figure9 — Heat Strengthened glass fixed on two opposite sides 
5 Installation 
5.1 Basic installation requirements  
The basic installation requirements and materials used for glass are given below: 
a) the provisions under this item does not include the use of other methods or systems for glazing, provided 
that the alternate method or system can be demonstrated to satisfy the requirements for correctly 
supporting the glass within the frame or glazing system; 
b) patent and other proprietary systems are not described/covered in this section;and 
DRS 397-4: 2023 
37                ©RSB2022- All rights reserved 
 c) installation technique for frameless glazing system is not covered in this in this section.  
5.1.1 Site working and glass machining operation 
Heat-strengthened and toughened glass shall not be cut or worked after heat treatment. All necessary cutting, 
drilling, notching, and edge-working shall be carried out to correct dimensions prior to value addition to the 
glass such as toughening/ tempering/ heat strengthening. The edges and surfaces of all glass types shall not 
be damaged during fixing. Glass damaged during or prior to installation shall not be installed. 
5.1.2 Dimensional requirement 
The dimensions for edge clearance, edge cover, front and back clearance, rebate depth shall be selected in 
accordance RS 397-2. 
5.2 Glazing materials 
5.2.1 Compatibility of materials 
A glazing material shall be used only when compatible with contiguous materials, including the rebate surface 
finish, setting or location blocks, distance pieces and glass type are available .  
5.2.2 Application of materials 
The application of glazing materials shall be in accordance with relevant/available standard or manufacturer's 
instructions.  
5.2.3 Life expectancy of materials 
A glazing material shall only be used where its life expectancy (durability) has been established. The 
manufacturers’ advice/guarantee should be sought for information regarding life expectancy.  
5.3 Setting blocks 
5.3.1 The number and location of setting blocks shall be as shown in figures 13 and 14. Generally, setting 
blocks shall be: 
a) positioned at quarter points or not less than 30 mm from the corner, whichever is lesser;  
b) the minimum width of each setting block shall be not less than the glass thickness; and  
c) the minimum thickness of the setting block for drained glazing systems shall be 6 mm.  
5.3.2 Setting blocks shall be located to equally support all panes of glass, and shall be fixed to prevent 
displacement during installation and service.  DRS 397-4: 2023  
©RSB 2023- All rights reserved                  38 5.3.3 The minimum length of each setting block (or two blocks side by side) shall be 25 mm in length for 
every square meter of glass area, with a minimum length of 50 mm.  
5.3.4 When wood is used as the material for setting blocks, only the seasoned ones should be used as 
green wood may shrink laterally (in the process of attaining equilibrium moisture content over a period of time) 
and result in loosened installations.  
NOTE For example, a 3.0 m2glass area, 3.0 × 25 mm = 75 mm long, i.e., 75 mm is the length of each setting block.  
5.3.5 Setting blocks shall be of resilient, load-bearing, non-absorbent, rot-proof, and material that is 
compatible with all other glazing materials conforming to available standards (if any) that may come into 
contact with the blocks. 
NOTE 1 Setting blocks are used between the bottom edge of the unit and the frame to centralize and equally support 
both panes of glass. 
NOTE 2 Setting block width and location should not restrict water drainage. 
NOTE 3 Extruded rubber material with 80 - 90 shore-A hardness is recommended. 
NOTE 3 Shaped setting blocks will be required for a glazing platform. 
 
 
 
 
a) Figure 12 — Position of setting block 
DRS 397-4: 2023 
39                ©RSB2022- All rights reserved 5.4 Location blocks 
The number and position of location blocks shall be as shown in figures 12 and 14. Location blocks shall be:  
a) of minimum of 25 mm in length;  
b) at least as wide as the glass thickness;  
c) positively located to prevent displacement in service; and  
d) sufficiently resilient to accommodate movement within the frame, without imposing stress on the 
glass, and of resilient, non-absorbent material.  
NOTE1 Location blocks are used between the edges of the glass and the frame to prevent movement of the glass 
within the frame by thermal expansion or when the window or door is opened or closed. They are required to prevent the 
weight of the glass from causing the frame to become out of square.  
NOTE 2 Extruded rubber material with 55 - 65 shore-A hardness is recommended. 
 
Figure 13— Position of location block 
 
DRS 397-4: 2023  
©RSB 2023- All rights reserved                  40  
Figure 14 — Recommended positions of setting and location blocks for the site glazing of some types 
of doors and windows 
DRS 397-4: 2023 
41                ©RSB2022- All rights reserved 5.5 Distance Pieces 
5.5.2 Distance pieces, as shown in Figure 15, used where required, shall be: 
a) of resilient, non-absorbent material;  
b) 25 mm long and of a height to suit the depth of the rebate and the method of glazing; and  
c) spaced opposite each other, approximately 50 mm from each corner at intervals of not more than 300 
mm.  
5.5.2 The thickness shall be equal to the front and back clearance, to retain the glass firmly in the frame.  
NOTE 1 Distance pieces are required to prevent displacement of glazing compounds or sealant by external loading, such 
as wind pressure 
NOTE 1 Extruded rubber material with 55 - 65 shore A hardness is required. 
 
Figure 15 — Position of distance pieces 
5.6 Rebates and grooves for installation 
5.6.1 Rebates, grooves and beads shall be cleaned and free from grease, moisture and other 
contaminants. All sealant surfaces shall be primed or sealed in accordance with the recommendations of the 
manufacturer of the glazing material.  
5.6.2 The number and location of setting blocks and location blocks shall be as shown in figures 12, 13 and 
14, wherever necessary to maintain the requisite edge clearance. Each block shall support the full thickness 
of the glass. 
DRS 397-4: 2023  
©RSB 2023- All rights reserved                  42 
 5.7 Glazing beads 
Where used, glazing beads shall be capable of restraining the glass under all design forces.  
5.8 Structural sealants 
5.8.1 Structural silicone shall be installed such that a full adhesive bond to the substrate is achieved. 
Application of structural silicone may require prior cleaning and or priming of the substrate.  
5.8.2 Applied structural silicones shall not be installed adjacent to other materials that may be chemically 
incompatible with the structural sealant and cause a loss of adhesion or adverse chemical changes within the 
structural silicone that could lead to a loss of strength in the structural silicone.  
NOTE For guidance on the installation of structural silicone, see ASTM C 1401 and ASTM C 1184. 
6 Design criteria 
6.1 Frame support condition 
6.1.1 Maximum area of glass panels subjected to wind loading 
6.1.1.1 The maximum span for a given standard nominal thickness of ordinary annealed, laminated, heat-
strengthened and toughened glass for a given panel size shall be determined in accordance with clause 6.2, 
6.3 and 6.4as applicable for the relevant support conditions. For heat strengthened laminated and toughened 
laminated glass, maximum allowable span shall be determined in accordance with 6.3. For 3 mm monolithic 
annealed glass, the maximum area shall not exceed 0.85 m2.  
6.1.1.2 The minimum thickness of the nominal glass size shall be as given in the respective specification 
standards in Annex A. 
6.1.1.3 For laminated glass composites, the combined minimum thickness of the glass sheets shall be used 
excluding the interlayer thickness. 
6.2 Rectangular glass supported on all four edges 
For rectangular glass supported on all four edges, the maximum area for the design wind pressure shall be 
determined either graphically from figures 6 to 9 or using the corresponding tables provided above the figure 
for each type of glass. Linear interpolation may be used for any value in between those given therein while 
maintaining the aspect ratio. 
6.3 Rectangles of glass supported on two opposite edges 
For rectangles of glass supported on two opposite edges, the maximum glass area for the design wind 
pressure shall be determined from figures 6 to 9 for ordinary annealed, laminated, heat-strengthened and 
toughened glass respectively.  DRS 397-4: 2023 
43                ©RSB2022- All rights reserved 
 6.4 Rectangles of glass supported on three edges 
For rectangles of glass supported on three edges, the maximum glass area shall be determined as for two-
edge support spanning along the unsupported edge. Alternatively, basic engineering principles shall be 
adopted in determining the glass thickness for all applications where only three edges of the panel are 
supported. 
NOTE Butt glazing of adjacent panels in the same plane should not be considered as a support when using figures 6 to 
13. 
6.5 Heat-strengthened laminated and toughened laminated glass 
For heat-strengthened laminated and toughened laminated glass, the maximum span for a given standard 
nominal thickness for a given panel size shall be determined from figures 5 and 9 and figures 2 and 7 
respectively, with the design wind pressure being divided by the appropriate glass type factor, P f (see Table 2), 
as applicable for the relevant support conditions.  
6.6 Serviceability checks 
6.6.1 Glass complying with Tables7 to 15 are deemed to meet the serviceability deflection limits specified (in 
the absence of any other specified values) or the following values may be had for guidance.  
6.6.2 Maximum allowable deflection of framing members 
a) for mullions: 
1) single height glazing: Span/175 or 19mm whichever is less; and 
2) double height glazing: For spans up to 4110 mm, same as single height glazing; and for spans 
above 4110mm, the same shall be (Span/240) + 6.35 mm. 
b) for transoms: 
1) span/500 or 3 mm, whichever is the least for dead load; and 
2) span/175 or 19 mm, whichever is the least for wind load. 
c) deflection at the centre of the glass: 
1) monolithic glass: shorted span/60 or 19 mm, whichever is the least; and 
2) double glazed unit: shortest span/90 or 19 mm, whichever is the least. 
d) deflection at the edge of the glass shall be limited to 15 mm. DRS 397-4: 2023  
©RSB 2023- All rights reserved                  44 
 6.7 Ultimate stresses 
The ultimate stresses for various types of glass are given in Table 16. 
6.8 Insulating glass units 
6.8.1 Determining thickness of structural silicone 
The structural bite requirement is directly proportional to the wind load and the dimension of glass. Higher the 
wind load and larger the dimensions of the glass are, the greater the amount of structural bite required. The 
controlling variables which affect the structural bite requirement are the maximum short span dimension of 
glass and the design wind load that the structural glazing system must be designed to accommodate. 
Table 16 — Ultimate limit state design stresses for glass subjected to wind loading 
Glass type Standard nominal 
thickness 'T' Ultimate limit state design stress at given 
location 
mm Away from edge (Mpa) At edge (Mpa) 
Annealed 3 41 32.8 
4 38.99 31.19 
5 37.45 29.96 
6 36.2 28.96 
8 34.33 27.46 
10 32.8 26.24 
12 31.57 25.25 
15 30.15 24.12 
19 28.72 22.98 
25 26.96 21.57 
Toughened 4 97.47 77.97 
5 93.61 74.97 
6 90.49 72.39 
8 85.82 68.65 
10 82.01 65.61 
12 78.91 63.13 
15 75.37 60.3 
19 71.81 57.45 
25 67.41 53.93 
Heat 
strengthened 3 65.6 52.8 
4 62.38 49.9 DRS 397-4: 2023 
45                ©RSB2022- All rights reserved 5 59.91 47.93 
6 57.91 46.33 
8 54.92 43.94 
10 52.48 41.99 
12 50.51 40.4 
Annealed 
laminated 5 37.73 30.18 
6 36.43 29.14 
8 34.41 27.53 
10 32.87 26.3 
12 31.62 25.3 
16 29.75 23.8 
20 28.23 22.58 
24 26.99 21.59 
 
 
Figure 14 — Typical structural glazing detail 
6.8.1.1 Structural bite calculation for wind load and glass dimension  
Minimum Structural Bite = (Glass Short Span Dimension * Wind Load * 0.5)/Maximum allowable design 
stress  
NOTE 1 Glass' Short Span Dimension (SSD) is the shorter of the two dimensions (in metre) of the rectangular glass 
panel. 
DRS 397-4: 2023  
©RSB 2023- All rights reserved                  46 
 NOTE 2 Wind load is the maximum wind pressure in Pascal for a return period of 10 years based on local regulations. 
NOTE 3 The maximum allowable design stress for type of the structural sealant is selected. 
6.8.1.2 Structural bite calculation for dead load 
Minimum bite (m) = ௐ௘௜௚௛௧௢ௗ௚௟௔௦௦  (௞௚)
௉௘௥௜௠௘௧௘௥௢௙௧௛௘௚௟௔௦ (௠) ×௦௘௔௟௔௡௧ௗ௘௔ௗ௟௢௔ௗௗ௘௦௜௚௡௦௧௥௘௡௚௧௛ ቀ௞௚
௠మൗ ቁ= ఘ௚்஺
௉ௌ 
ρ = 2500 kg/m3is the specific mass of flat glass corresponding to approximately of specific weight.  
g = 9.81 m/S2 
S = Allowable Design Stress for Dead load (DL) for selected sealant considered for design, Pa.  
T= thickness of the bite, m 
P = perimeter (if the horizontal frame members will not be supporting the glass or will deflect under the 
dead load of the glass, consider 2 x Height only)  
A = area of glass panel (m2)  
6.8.2 Maximum allowable span for glass and type 
Maximum allowable span is dependent on the thickness of the glass selected and type of glass used (e.g., 
annealed, toughened or heat strengthened glass). The maximum span is calculated in accordance with 4.9.  
6.9 Safety during installation 
6.9.1 Glass and the coating layer (if any) should not be, exposed to/in direct contact, with aggressive 
materials such as acid, solvent, cement mortar, etc. 
6.9.2 The fixing system of the panel should in no case, cause shear stresses in the panel, and particularly 
the bonding interface between the glass sheet and the frame, either under the effect of external forces or due 
to differential expansion of components.  
6.9.3 The protection of glass panel by means of a polyethylene sheet is recommended and shall provide 
ventilation for the glass in order to prevent thermal breakage. 
6.10 Handling and transportation 
6.10.1 Transportation 
During transportation of flat glass (clear, tinted), coated glass (solar control and mirror), lacquered or painted 
glass the following methods (if other standard packaging specifications are not available) of storage, packing 
and interleaving shall be followed:  DRS 397-4: 2023 
47                ©RSB2022- All rights reserved 
 a) flat glass shall be transported vertically;  
b) the glass panes should not come into direct contact with each other by using appropriate interleaving 
such as powder or foam or paper. The lacquer opacified / enamel coated / screen printed glasses 
shall be separated by paper or foam; and  
c) the packing and packing material shall be protected from water and if the glass is wrapped and 
sealed, the seal should remain closed until the product is used and precautions shall be taken not to 
damage the packing while handling with a hoisting apparatus.  
6.10.2 Handling 
During handling of flat glass (clear, tinted), coated glass (solar control and mirror), lacquered or painted glass, 
the following guidelines shall be followed: 
a) glass shall be handled with dry, clean gloves, specifically after washing to prevent stain marks on 
them; 
b) care shall be taken to avoid contact or friction of the coating or the opacified/enamel/screen printed 
side with any rough surface or hard objects; 
c) a better practice is to handle glass with vacuum cups, and ensure that the vacuum cups and the glass 
are clean; and  
d) it is recommended to keep it clean if glass sheets are stored again before their processing or 
installation in the facade.  
6.11 Storage at site 
To prevent staining, the storage area at site shall be:  
a) a dry, well-ventilated location at a sufficiently constant temperature;  
b) protected from rain and running water;  
c) protected from wide changes in temperature or humidity;  
d) protected from alkaline material;  
e) protected from direct contact of aggressive products such as corrosive vapours, acids, etc; and  
f) glass panes are stored vertically on a soft surface such as wooden boards/battens.  DRS 397-4: 2023  
©RSB 2023- All rights reserved                  48 
 6.12 Storage after cutting 
6.12.1 While stacking of coated glass/mirror in the unpacked condition, the glass surface shall be facing 
towards the front (paint/coating backing towards the back).  
6.12.2 Direct stacking of the mirror/coated glass one above the other should be prevented and suitable 
interleaving material as mentioned in 6.9 should be used between two glass panes. 
6.12.3 The support material for glass storage should not have affinity towards moisture absorption. 
7 Fire safety 
7.1 General 
7.1.1 This section covers the requirements and selection of fire safety glass for buildings. General fire safety 
provisions for buildings are found in relevant parts of RS 186. It is important for any fire rated glass to provide 
sufficient amount of human impact safety feature even during fire or in general situations. The level of human 
impact safety of glass in buildings shall be in accordance with DRS 387-5. Fire rated system shall withstand 
the standard time-temperature curve during a fire test and shall give adequate time to the occupants for safe 
evacuation. This section does not deal with the safety and security of people or goods in relation to risks of:  
a) vandalism, riots, burglary or break in protection; 
b) protection from explosion (terrorist attack); 
c) natural disasters like earthquakes, cyclone, etc.;and 
d) plastic glazing, safety and security glazing, etc.  
7.1.2 The requirements given in this section are minimum fire resistance requirements. In circumstances 
wherein the requirements of other Rwanda Standards exceed the requirements of this section, in such cases 
the higher requirements shall apply. 
7.2 Glass for fire resistance 
7.2.1 Glazing material shall be constructed, treated, or combined with other materials so as to reduce loss of 
life or property during an event of fire, in comparison with ordinary sheet or flat glass, thereby preventing the 
passage of flame, hot gases, smoke and/or providing radiation control and/or insulation.  
7.2.2 The following are the products in the scope of this section that may be used for fire resistance in glazing 
provided that they meet the relevant available standards:  
a) wired glass; 
b) Annealed Fire Resistant glass (AFG); 
c) Tempered Fire Resistant Glass (TFG); DRS 397-4: 2023 
49                ©RSB2022- All rights reserved 
 d) Gel Laminated Fire Resistant Glass (LFG); and 
e) Double Glazed Fire Resistant Glass (DFG). 
7.2.2.1 Wired glass is a type of glass into which a wire mesh is embedded during production. Wired glass has 
an impact resistance similar to that of normal glass, but in case of breakage, the mesh retains the pieces of 
glass. Value addition such as tempering and lamination is not possible using wired glass. 
NOTE Wired glass is not recommended in doors except as vision panel and for window sizes not greater than in 
Table 17. 
Table 17 — Limiting size of wired glass panel 
Opening fire 
protection rating Maximum area 
m2 Maximum 
height 
(m) Maximum width 
m 
60 to 90 min 0.0645 0.838 0.254 
45 min 0.836 1.372 1.372 
20 min Not limited Not limited Not limited 
Fire window assembly 0.836 1.372 1.372 
 
7.2.2.2 Annealed Fire Resistant Glass : A single piece of fire resistant glass that is tested for fire resistance 
for the required duration. These types of glasses can be used only in areas where human impact safety is not 
an issue, typically in areas like vision panels of doors.  
7.2.2.3 Tempered Fire Resistant Glass : A single piece of specially heat-treated or chemically treated glass 
that is tested for fire resistance for the required duration and which has a stress pattern such that the piece 
when fractured reduces to numerous granular fragments, with no large jagged edges. Additionally, these 
glasses should have an impact resistance of highest classification.  
7.2.2.4 Gel Laminated Fire Resistant Glass : Two or more pieces of fire resistant glass held together by an 
interleaving layer or layers of materials and that as a complete system is tested for fire resistance. The 
laminated glass will crack and break during the fire or under sufficient impact, but the pieces of glass tend to 
adhere to the interlayered material and do not allow the fire to penetrate the last layer of glass.  
7.2.2.5 Double Glazed Fire Resistant Glass : Fire resistant glass that is used as a double glazed unit has to 
be tested as a complete Double Glazed Unit (DGU) or other multiple glazed units as the case may be. Fire 
resistant glass cannot be combined with another glass and used as a DGU unless the combined double 
glazed or multiple glazed unit is also tested. Both the panes of the double glazed unit shall satisfy the required 
impact safety as mentioned in DRS 397-5.  
NOTE It may be noted that use of any fire rated glass has to be used in conjunction with a tested system. Fire rated 
glass alone cannot provide the desired fire resistance since the fire resistance of a partition or a door assembly or any 
glazed building element is a function of the glass, frames, hardware, gaskets and fixings which forms the glazed system.  DRS 397-4: 2023  
©RSB 2023- All rights reserved                  50 7.2.1 Testing procedures 
7.2.1.1 Any fire rated glazed building element needs to be tested as per ISO 3009. The standard tests any 
building element shall have to withstand against a fixed time – temperature curve is defined as:  
 
where  
T is the average furnace temperature in deg Celsius at time 't' in minutes  
7.2.1.2 Different standards have different pressure standards which have to be maintained as per the 
standard during the testing.  
7.2.1.3 The fire rating criteria of any building element is determined as per the following:  
a) integrity: prevention of passage of flames, hot gases and smoke from the fire side to the non-fire side, 
denoted by the letter (E); 
b) radiation control,the radiation performance category is defined at a qualifying maximum total heat flux of 
15Kw/Sqm. Values are determined based on measurements at standard distance of 1 mfrom the glazed 
element at the end of standard fire test time period. This criterion can be achieved by the use of fully 
insulating fire-resistant glass or by using integrity only glass types with additional radiation reducing 
property. Providing integrity along with keeping the radiated heat through the building element below 15 
kw/m2 when measured at a distance of 1 m from the building element, denoted by the letters (EW); and 
c) insulation: providing integrity along with keeping the average temperatures as measured by all the 
thermocouples on the non-fire side below 140 °C from the initial temperature considering that no 
thermocouple records a temperature more than 180 °C from the initial temperature at any point of time 
during the test, denoted by the letters (EI).  
7.2.2 Identification of glass used for fire resistance 
7.2.2.1 All glass used for resisting fire shall conform to and preferably be certified against ISO 3009 
requirements.  
7.2.2.2 Since a fire-resistant glass is not easily distinguishable from normal types of glass, it is imperative 
that every fire rated glass panel should preferably have an indelible mark on all the panels of fire-resistant 
glass showing the name of the manufacturer and the name of the product.  
7.2.2.3 Rating of the glass panel may also be provided, although the rating of glazing system is of 
primary concern.  
7.3 Precautions 
7.3.1 Fire-resistant glass alone will not be enough to protect occupants from fire. Glass is only one component 
of the complete system. 
DRS 397-4: 2023 
51                ©RSB2022- All rights reserved 
 7.3.2 Fire test certificate report conducted for one application shall not be substituted for any other application.  
7.3.2.1 For example, a report for a partition shall not be used for a door application although the glass 
used and the fire ratings are the same.  
7.3.2.2 Approval in vertical orientation cannot be considered for acceptance in horizontal or inclined 
orientation.  
7.3.3 The maximum glass size as mentioned in the test report should not be exceeded in practice with respect 
to the bigger linear dimension or area, unless otherwise validated by an assessment report issued by the 
testing laboratory. The aspect ratio may be modified provided that none of the linear sides has a dimension 
greater than that of the largest dimension of originally tested glass.  
7.3.4 The dimensions of the profile need to be the same as that tested.  
7.3.5 In case of any change in hardware, they should be replaced following the guidelines laid down in the 
standard against which the test was conducted.  
7.3.6 Factors like edge cover, types of gaskets and type of fixtures also play a very vital role in achieving the 
fire performance of the building element. These have to be used and installed as per the test report/available 
standards.  
7.4 Application 
The use of application of fire safety glass in building shall be in concurrence with the requirement of available 
Rwandan Standards and other regulations in force.  
7.4.1 Horizontal exit shall be equipped with atleast one fire/smoke door of minimum one hour-fire resistance 
of self-closing type. Further, it is required to have direct connectivity to the fire escape staircase for 
evacuation.  
7.4.2. Exit doorways ,every exit doorway shall open into an enclosed stairway or a horizontal exit of a corridor 
or passageway providing continuous and protected means of egress. The exit doorway should have a 
minimum dimension of 1000 x 2000 mm.  
7.4.3 Lift walls of lift shaft enclosures shall have a fire rating of 2 h.  
7.4.4 Lift shafts shall have a vent at the top, of area not less than 0.2 m2; lift motor room shall be located 
preferably at the top of the shaft and separated from the shaft by the floor of the room.  
7.4.5 Landing doors in lift enclosures shall have fire resistance of not less than 1h. A wall of 2 h rating shall 
separate individual shafts in a bank. 
7.4.6 Lift car door shall have a fire resistance rating of half an hour. Collapsible gates shall not be permitted 
for lifts. They shall have solid doors with fire resistance of at least 1 h.  
7.4.7 Exit from the lift lobby if located in the core of the building, shall be through a self-closing smoke stop 
door of half an hour fire resistance.  DRS 397-4: 2023  
©RSB 2023- All rights reserved                  52 
 7.4.8 Basement - the staircase of basements shall be of enclosed type having fire resistance of not less than 2 
h and shall be situated at the periphery of the basement to be entered at ground level only from the open air 
and in such positions that smoke from any fire in the basement shall not obstruct any exit serving the ground 
and upper storey of the building. It shall communicate with basement through a lobby provided with fire 
resisting self closing doors of one hour resistance. Glazing if used in staircase shall have fire resistance rating 
of minimum 2 h.  
7.4.9 Separation wall - All floors shall be compartmented with area not exceeding 750 m 2 by a separation wall 
with 2 hours fire rating. For floors with sprinklers the area may be increased by 50 %. In long building, the fire 
separation walls shall be at distances not exceeding 40 m. For departmental stores, shopping centers and 
basements, the area may be reduced to 500 m 2 for compartmentation. 
Table 18 — Fire resistance rating of structural and non-structural element 
S/N Structural element Type of construction 
Type 1 Type 2 Type 3 Type 4 
1 2 3 4 
h h h h 
1 Exterior wall    
 a) Fire separation less than 3.7 m i) Bearing  4 2 2 1 
ii) Non-bearing 2 2.5 1 1 
b) Fire Separation less than 3.7 m or more but less 
than 9m i) Bearing  4 2 2 1 
ii) Non-bearing 1.5 1 1 1 
c) Fire separation of 9m or more i) Bearing  4 2 2 1 
ii) Non-bearing 1 1 1 1 
2 Fire resisting wall   4 2 2 2 
3 Fire separation assemblies (like fire check doors)   4 2 2 2 
4 Fire enclosure of exitways elevators and staircases   2 2 2 2 
5 Shaft other than exitways elevators and hoist ways   2 2 2 2 
6 Exitway access corridor   1 1 1 1 
7 Vertical separation of tenant space   1 1 1 1 
8 Dwelling unit separation non-load bearing 
partitions   1 1 1 1 
at least half an hour 
9 Interior bearing walls, bearing partitions, columns, 
grinders, trusses (other than roof trusses) and 
framing i) supporitng more one 
floor 4 2 2 2 
ii) supporting one floor only 3 1.5 1 1 
iii) supporting roof only 3 1.5 1 1 
10 Structural members support walls   3 1.5 1 1 
11 Floor construction including walls   3 1.5 1 1 DRS 397-4: 2023 
53                ©RSB2022- All rights reserved 
 12 
roof construction i) 5m or less height to 
lowest member 2 1.5 1 1 
  ii) more than 5mm but less 
than 6.7mm in height to 
lowest member 1 1 1 1 
  iii) 6.7m or more in height 
to lowest member  0 0 0 0 
7.5 Installation of fire-resistant glazing system 
7.5.1 General requirements 
7.5.1.1 Installation is just as important as correct selection of the system. Any number of test and assessment 
conducted on the system are completely undermined if the installation is sub-standard.  
7.5.1.2 Decisions concerning changes to the specified fire-resistant glazing system should not be made on 
site.  
7.5.1.3 Specific instructions given by manufacturers should be noted and strictly followed, and this applies in 
particular to labels indicating glazing orientation and direction.  
7.5.2 Specific glazing provisions 
7.5.2.1 The following shall be checked during installation:  
a) thermal expansion elements (which may be glass type specific); 
b) application and location of setting blocks; 
c) glazing seal as specified in test certificate; 
d) application of correct type of bead with secure fixing; 
e) edge cover in view of its importance; 
f) amount of edge cover on glass in its frame can be a critical dimension for the following reasons; 
1) the performance of tempered fire-resistant glass is critically dependent on the edge cover and 
edge clearance; and 
2) for some types of glass, the edge cover is not as per the test certificate. Then it is quite possible 
that the glass may fail due to slumping.  
7.5.2.2 Before installing the glass, the work area shall be checked for dimensions, plumb and any obstructions 
like running cables, etc.  DRS 397-4: 2023  
©RSB 2023- All rights reserved                  54 
 7.5.2.3 Frames shall be securely installed to the supporting structure by means of suitable systems such as 
expanding metal bolts, screws, etc. The design guidelines/test reports' specification/values need to be 
adhered to while fixing the glazing.  
7.6 Critical location 
7.6.1 General 
Parts of a building that are most likely to be used for exit or movement in the event of a fire, are the critical 
locations from fire safety point of view.  
7.6.2 Classification 
Any glazing within the above critical location area requiring fire resistance, shall necessarily comply with both 
the fire resistance and impact safety requirements , as per relevant part of RS 186.  
 
 
  DRS 397-4: 2023 
55                ©RSB2022- All rights reserved 
 Annex A 
(informative)  
 
Procedure for calculation of the approximate deflection at centre of glass 
panel 
A.1 Maximum glass deflection as a function of plate geometry and load may be calculated using the 
following: 
Deflection (w) = 𝑡.exp(𝑟଴+ 𝑟ଵ𝑋+ 𝑟ଶ𝑋ଶ) 
where 
𝑋 =  𝑙𝑛{𝑙𝑛[𝑞   (𝑎.𝑏 )ଶ / 𝐸𝑡ସ]} 
𝑟଴ =  0.553−3.83 ቀ𝑎
𝑏ቁ+1.11 ቀ𝑎
𝑏 ቁଶ
−0.0969  ቀ𝑎
𝑏 ቁଷ
 
𝑟ଵ = −2.29+5.83 ቀ𝑎
𝑏ቁ−2.17 ቀ𝑎
𝑏 ቁଶ
+0.2067  ቀ𝑎
𝑏 ቁଷ
 
𝑟ଶ =  1.485−1.908 ቀ𝑎
𝑏ቁ+0.815 ቀ𝑎
𝑏 ቁଶ
−0.0822  ቀ𝑎
𝑏 ቁଷ
 
where  
E is Young’s modulus of glass, N/mm2; 
q is net pressure on the pane, N/mm2; 
a is longer dimension, mm; 
b is shorter dimension, mm; 
t is thickness of the glass pane calculated, mm. 
Example: Lateral Deflection Calculation in SI Units  
Determine the maximum lateral deflection (w) of a vertical 1200 𝑚𝑚×1500 𝑚𝑚×6 𝑚𝑚 rectangular glass 
plate subjected to a uniform lateral load of 1.80 kPa. The actual thickness of the glass is 5.60 mm as 
determined through direct measurement.  
a = 1500; b = 1200  DRS 397-4: 2023  
©RSB 2023- All rights reserved                  56 
 r0 = −2.689  
r1 = 2.011  
r2 = 0.213  
q = 1.80  
E = 71.73 x 106  
t = 5.60  
x = 1.490  
Therefore, the maximum deflection at the centre of glass is: 
w = 5.6 x exp(−2.689 + 2.111 x 1.490 + 0.213 x 1.4902)  
w = 12.2 mm  
 
 
 
 
 
 
 
 
 
 
 
 DRS 397-4: 2023 
57                ©RSB2022- All rights reserved 
 Annex B 
(informative)  
 
Model calculation of glass thickness 
B.1 Model calculation  
B.1.1 Glass panel dimension width 1200mm and height 1800mm for location Chennai for annealed glass 
type  
B.1.2  General checks has to be done for safety performance:  
a)  the maximum area of glass panel is restricted to 15 m2; 
b) thethe maximum span of window is restricted to 4 m; 
c)  applicable to normal, reflective, laminated, tempered and insulating glass; and 
d)  applicable to rectangular panels properly fixed.  
B.2 Procedure for calculating glass thickness 
Step 1: Calculate Aspect Ratio ( 𝐴𝑅௠௔௫) from Table 3.  
Aspect ratio ( 𝐴𝑅௠௔௫) = Longer side/shorter side of glass  
Aspect ratio = 1800/1200 = 1.5  
Step 2: Wind load calculation 
𝑃௓= 0.6 𝑉௓ଶ 
𝑉௓= 𝑉௕𝑘ଵ𝑘ଶ𝑘ଷ𝑘ସ  
where  
𝑉௕  Basic Wind Speed based on Location (Table 1); 
𝑘ଵ  Risk Co-efficient factor taken as per; 
𝑘ଶ  Terrain Factor (Table 2); DRS 397-4: 2023  
©RSB 2023- All rights reserved                  58 
 𝑘ଷ  Topography Factor; 
𝑉௓  Design Wind Speed; 
𝑃௓  Design Wind Pressure N/m2at Height H. 
Design wind Speed for Chennai location (basic wind speed = 50m/s) = 1750 N/m2 
Step 3: Strength factor  
Based on the types of glass (Laminated/Tempered/Insulating glass) pressure factor is calculated. To 
determine the thickness of laminated/tempered/insulating glass, the design wind pressure 𝑃௡௘௧is modified as 
below:  
𝑃௡௘௧= 𝑃௭/ 𝑃௙ 
where 
𝑃௙is the pressure factor dependent on the type of glass  
The values of the pressure factor 𝑃௙can be taken from Table 2.  
For Annealed Units, 
𝑃௙= 1.0  
𝑃௡௘௧= 1750/1.0 = 1750 N/m2 
At this Stage the glass thickness value been calculated from the table and then the deflection and Stress 
check been done  
B.3 Deflection calculation  
The deflection of the glass can be calculated using the formula in Annex A .  
Actual deflection for the pane:  
Deflection (w) = 𝑡.exp(𝑟଴+ 𝑟ଵ𝑋+ 𝑟ଶ𝑋ଶ) 
where  
𝑋 =  𝑙𝑛{𝑙𝑛[𝑞   (𝑎.𝑏 )ଶ / 𝐸𝑡ସ]} 
𝑟଴ =  0.553−3.83 ቀ𝑎
𝑏ቁ+1.11 ቀ𝑎
𝑏 ቁଶ
−0.0969  ቀ𝑎
𝑏 ቁଷ
 DRS 397-4: 2023 
59                ©RSB2022- All rights reserved 
 𝑟ଵ = −2.29+5.83 ቀ𝑎
𝑏ቁ−2.17 ቀ𝑎
𝑏 ቁଶ
+0.2067  ቀ𝑎
𝑏 ቁଷ
 
𝑟ଶ =  1.485−1.908 ቀ𝑎
𝑏ቁ+0.815 ቀ𝑎
𝑏 ቁଶ
−0.0822  ቀ𝑎
𝑏 ቁଷ
 
where  
E IS Young’s modulus of glass, N/mm2; 
q is net pressure on the pane, N/mm2; 
a is longer dimension, mm; 
b is shorter dimension, mm; and 
t is thickness of the glass pane calculated, mm. 
The Actual deflection is, 4mm < 11mm maximum allowable  
Result: 1800 / 175 = 10.3 mm maximum allowable deflection.  
Hence the glass thickness calculated is safe against deflection.  
Glass thickness calculation  
𝑃௡௘௧×𝐴= 200.3 𝑇௞(𝑙𝑒𝑡𝑇≤ 6 𝑚𝑚 
𝑃௡௘௧= = 1750  
A = 2.16 m2 
K = 1.765  
T = 5.28 mm, therefore choose the thickness of glass as 6mm 
 
 
 
 
 DRS 397-4: 2023  
©RSB 2023- All rights reserved                  60 Annex C 
(informative)  
 
Installation of mirrors 
C.1 This annex provides general guidelines, which is to be followed during the installation of mirror. Mirrors 
(piece of glass silvered on one side, with a protective paint coating) are used in shops, gymnasiums, etc., 
where it is predominantly used as wall cladding. The mirror panels in such application use large panel size 
and it is recommended to follow the installation procedure in accordance with this annex.  
C.1.1 The mirror should always be mounted on a perfectly flat, clean and dry surface free from acids and 
aggressive substances such as acid, solvent and cement mortar.  
C.1.2 The mirror shall be mounted on wall or plywood and care is taken that the mirror is never stuck over 
unstable support (painted paper, paint or old plaster). It is recommended that the mirror installation is not done 
directly the mirrors supporting in order to have good ventilation, following is recommended space depending 
on the height of the mirror panel: 
a) a space of 5 mm for a mirror less than 1 m height;and 
b) a space of 10 mm for a mirror greater than 1 m height.  
 
Figure C.1 — Installation of mirrors 
C.1.3 During the installation of mirror panels at several levels i.e., one above the other, it is recommended 
to provide a space of 10 mm at the top and at the bottom for circulation of air. The side of the mirror is 
designed with a minimum 1 or 2 mm of interleaving space. When mirror is fixed in a profile (frame), care is to 
be taken to maintain perfectly dry and clean frame.  
C.1.4 It is recommended that mirror is supported on hard non-metallic/plastic wedges of at least 3 mm, to 
raise the mirror and thus avoid contact with the condensed water which could accumulate in the profile. If the 
mirror is screwed on, the screws of a suitable dimension is designed, with the interleaving and washers made 
DRS 397-4: 2023 
61                ©RSB2022- All rights reserved of plastic to avoid any direct glass-metal contact. To minimize the risk of breakage, cracks and splinters during 
screw-mounting the mirror, it is recommended to use synthetic protective collars 
 
Figure C.2 — Plastic washer 
C.1.5 The adhesive used to mount mirrors; care should be taken to ensure that the adhesive is compatible 
with the protective coatings on the mirror. It is recommended to use only neutral binding agents such as 
Alkoxy silicone, Oxime silicone, etc. Avoid use of acid silicones, such as Acetoxy silicones which contain 
acetic acid or water/rubber/polyurethane-based glues. 
 
Figure C.3 — Details of double sided adhesive tapes for installing mirrors  
C.1.4 In the high humidity areas (e.g. bathrooms), it is recommended to seal the edges with neutral silicone 
to protect the backing paint from damage due to moisture and enhanced protection from moisture. It is 
recommended to use double sided adhesive tapes to fix the mirror on the mounting surface. The adhesive 
DRS 397-4: 2023  
©RSB 2023- All rights reserved                  62 
 tapes used for installation must be certified to be compatible with the mirror and the adhesive or the adhesive 
tapes must always be fixed vertically. 
 
 DRS 397-4: 2023 
63                ©RSB2022- All rights reserved 
 Annex D 
(informative)  
 
Response reduction factor R for building systems 
S/N Lateral load resisting system R 
i. Moment frame systems 
a) RC buildings with ordinary moment resisting frame (OMRF)a 3.0 
b) RC buildings with special moment resisting frame (SMRF) 5.0 
c) Steel buildings with ordinary moment resisting frame (OMRF)a 3.0 
d) Steel buildings with special moment resisting frame (SMRF) 5.0 
ii. Braced Framr Systemsb 
a) Buildings with ordinary braced frame (OBF) having concentric braces 4.0 
b) Buildings with special braced frame (SBF) having concentric braces  4.5 
c) Buildings with special braced frame (SBF) having eccentric braces  5.0 
iii. Structural Wall Systems3 
a) Load bearing masonry buildings 
1) Unreinforced masonry without horizontal RC seismic bandsa 
1.5 
2) Unreinforced masonry with horizontal RC seismic bands  
2.0 
3) Unreinforced masonry with horizontal RC seismic bands and vertical 
reinforcing bars at corners of rooms and jambs of openings  2.5 
4) Reinforced masonry  
3.0 
5) Confined masonry 
3.0 
b) Buildings with ordinary RC structural wallsa 
3.0 
c) Buildings with ductile RC structural walls 
4.0 
iv. Dual systemsc 
a) Buildings with ordinary RC structural walls and RC OMRFsc 3.0 
b) Buildings with ordinary RC structural walls and RC SMRFsa 4.0 
c) Buildings with ductile RC structural walls and RC OMRFsa 4.0 
d) Buildings with ductile RC structural walls and RC SMRFs  5.0 
v. Flat Slab- Structural Wall Systemsd 
RC building with the three given below: 
a) ductile RC structural walls (which are designed to resist 100% of the 
design lateral force); 
b) perimeter RC SMRFs (which are designed to independently resist 25 3.0 DRS 397-4: 2023  
©RSB 2023- All rights reserved                  64 
 percent of the design lateral force), and preferably; and 
c) an outrigger and belt truss system connecting the core ductile RC 
structural walls and the perimeter RC SMRFsa. 
NOTES:. 
a RC and steel structures in seismic zones V, VI and VII shall be designed to be ductile. Hence, this system is not allowed in 
these seismic zones. 
b Eccentric braces shall be used only with SBFs. 
cBuildings with structural walls also include buildings having structural walls and moment frames, but where; 
Frames are not designed to carry design lateral loads, or 
Frames are designed to carry lateral loads, but do not fulfil the requirements of ‘Dual Systems. 
d In these buildings, (a) punching shear failure shall be avoided, and (b) lateral drift at the roof under design lateral force shall not 
exceed 0.1%.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 DRS 397-4: 2022 
1                ©RSB2022- All rights reserved 
 Bibliography 
[1] RS ISO 16293-1: 2008, Glass in building — Basic soda lime silicate glass products — Part 1: 
Definitions and general physical and mechanical properties  
[2] RS ISO 16293-2: 2017, Glass in building — Basic soda lime silicate glass products — Part 2: Float 
glass 
[3] RS ISO 12543-1: 2011, Glass in building — Laminated glass and laminated safety glass — Part 1: 
Definitions and description of component parts  
[4] RS ISO 12543-2: 2011, Glass in building — Laminated glass and laminated safety glass — Part 2: 
Laminated safety glass 
[5] RS ISO 12543-3: 2011, Glass in building — Laminated glass and laminated safety glass — Part 3: 
Laminated glass 
[6] RS ISO 12543-4: 2011, Glass in building — Laminated glass and laminated safety glass — Part 4: 
Test methods for durability 
[7] RS ISO 12543-5: 2011, Glass in building — Laminated glass and laminated safety glass — Part 5: 
Dimensions and edge finishing 
[8] RS ISO 12543-6: 2011, Glass in building — Laminated glass and laminated safety glass — Part 6: 
Appearance 
[9] RS ISO 12540: 2017, Glass in building — Tempered soda lime silicate safety glass  
[10] ISO 16935, Glass in building ― Bullet-resistant security glazing ― Test and classification 
[11] ASTM C 1401-14, Standard Guide For Structural Sealant Glazing  
[12] ASTM C 1184-18, Standard Specification For Structural Silicone Sealants  
 DRS 397-4: 2023 
 
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