NEPAL NATIONAL BUILDING CODE
NBC 109 : 1994

MASONRY : UNREINFORCED

Government of Nepal

Ministry of Physical Planning and Works
Department of Urban Development and Building Construction
Babar Mahal, Kathmandu, NEPAL

Reprinted : 2064

NBC108V2.RV9

7 December 1993

NEPAL NATIONAL BUILDING CODE
NBC 109 : 1994

MASONRY : UNREINFORCED
This publication represents a standard of good practice and therefore
takes the form of recommendations. Compliance with it does not confer
immunity from relevant legal requirements, including bylaws
tTsflng >L % sf] ;/sf/ -dlGqkl/ifb\_ sf] ldlt @)^).$.!@ sf] lg0f{ofg';f/ :jLs[tGovernment of Nepal

Ministry of Physical Planning and Works
Department of Urban Development and Building Construction
Babar Mahal, Kathmandu, NEPAL

Reprinted : 2064

NBC108V2.RV9

7 December 1993

i

PrefaceThis Nepal Standard was prepared during 1993 as part of a project to prepare a National Building
Code for Nepal.
In 1988 the Ministry of Housing and Physical Planning (MHPP), conscious of the growing needs of
Nepal's urban and shelter sectors, requested technical assistance from the United Nations Development
Programme and their executing agency, United Nations Centre for Human Settlements (UNCHS).
A programme of Policy and Technical Support was set up within the Ministry (UNDP Project
NEP/88/054) and a number of activities have been undertaken within this framework.
The 1988 earthquake in Nepal, and the resulting deaths and damage to both housing and schools, again
drew attention to the need for changes and improvement in current building construction and design
methods.
Until now, Nepal has not had any regulations or documents of its own setting out either requirements
or good practice for achieving satisfactory strength in buildings.
In late 1991 the MHPP and UNCHS requested proposals for the development of such regulations anddocuments from international organisations in response to terms of reference prepared by a panel ofexperts.
This document has been prepared by the subcontractor's team working within the Department of
Building, the team including members of the Department and the MHPP. As part of the proposedmanagement and implementation strategy, it has been prepared so as to conform with the general
presentation requirements of the Nepal Bureau of Standards and Metrology.
The subproject has been undertaken under the aegis of an Advisory Panel to the MHPP.
The Advisory Panel consisted of :Mr. UB Malla, Joint Secretary, MHPP
Director General, Department of Building(Mr. LR Upadhyay)
Mr. AR Pant, Under Secretary, MHPP
Director General, Department of Mines & Geology(Mr. PL Shrestha)
Director General, Nepal Bureau of Standards & Metrology(Mr. PB Manandhar)
Dean, Institute of Engineering, Tribhuvan University(Dr. SB Mathe)
Project Chief, Earthquake Areas Rehabilitation &Reconstruction Project
President, Nepal Engineers Association
Law Officer, MHPP (Mr. RB Dange)
Representative, Society of Consulting Architectural &Engineering Firms (SCAEF)

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ChairmanMemberMemberMemberMemberMemberMemberMemberMemberMember

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Representative, Society of Nepalese Architects (SONA)
Deputy Director General, Department of Building,(Mr. JP Pradhan)

MemberMember-Secretary

The Subcontractor was BECA WORLEY INTERNATIONAL CONSULTANTS LTD. of New
Zealand in conjunction with subconsultants who included :Golder Associates Ltd., Canada
SILT Consultants P. Ltd., Nepal
TAEC Consult (P.) Ltd., Nepal
Urban Regional Research, USA
Principal inputs to this standard came from :Mr. AM Tuladhar, DoB, HMGN
Dr. AS Arya, Professor Emeritus, University of Roorkee, India
Dr. RD Sharpe, BECA (Team Leader)

Revisions and Updated to this code came from :Mr. Purna P. Kadariya, DG, DUDBC
Mr. Kishore Thapa, DDG, DUDBC
Mr. Mani Ratna Tuladhar, Sr. DIV. Engineer, DUDBC
Mr. Jyoti Prasad Pradhan, Ex.DG, DOB
Mr. Bhubaneswor Lal Shrestha, Ex. DDG, DOB
Mr. Uttam Shrestha, Architect, Architects' Module Pvt. Ltd.
Mr. Manohar Lal Rajbhandhari, Sr. Structural Engineer, Mr Associates
Mr. Amrit Man Tuladhar, Civil Engineer, DUDBC

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TABLE OF CONTENTS
Preface......................................................................................................................................................... i0

Foreword...................................................................................................................................... vii

0.1
0.2

Design Aspects Covered ....................................................................................... .......... .......... vii
Related Codes

1

Scope .............................................................................................................................................. 1
1.1
1.2
1.3

2

Interpretation ............................................................................................................................... 1
2.1
2.2
2.3

3

Area Cover ....................................................................................................................... 1
Limitation......................................................................................................................... 1
Provisions for Historical Buildings............................................................................... 1

General.............................................................................................................................. 1
Terminology..................................................................................................................... 1
Symbols............................................................................................................................. 2

Materials........................................................................................................................................ 3
3.1
3.2
3.3
3.4

Material Used................................................................................................................... 3
Masonry Unit ................................................................................................................... 3
Tolerances ........................................................................................................................ 4
Classification of Bricks and Brickwork ....................................................................... 5
3.4.1
3.4.2

3.5
4

First Class Brickwork........................................................................................ 5
Limitation ............................................................................................................ 5

Mortar............................................................................................................................... 5

General Construction and Design Requirements ................................................................... 7
4.1
4.2
4.3
4.4

General.............................................................................................................................. 7
Selection of Mortar ......................................................................................................... 7
Thickness of Walls .......................................................................................................... 7
Stability Requirements ................................................................................................... 8
4.4.1
4.4.2

4.5

Parapets and Compound Walls .................................................................................... 9
4.5.1
4.5.2

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Lateral Support .................................................................................................. 8
Adequate Lateral Support ................................................................................ 8

General........................... ..................................................................................... 9
Free-Standing Walls........................................................................................... 919 May 1994

iv

4.5.3
4.5.4
4.5.5
4.6
4.7

Load Bearing Masonry Elements........................................................ 9
Slenderness Ratio................................................................................... 9
Curtain Walls ....................................................... ....................................9

Structural Design ............................................................................................................ 9
Design Method................................................................................................................ 10
4.7.1
4.7.2
4.7.3

Design Procedures ................................................................................ 10
Design Loads ......................................................................................... 10
Design of Wall Footings ....................................................................... 10
4.7.3.1 Depth of Footing........................................... ............................10
4.7.3.2 Width of Footing .................. ................................................... 11

4.7.4 Permissible Compressive Stresses........... ............................................... 11
5

General Requirements ............................................................................................................... 12
5.1
5.2

Deforming and Cracking .............................................................................................. 12
Cutting and Chasing...................................................................................................... 125.2.1 Stretches of Masonry ............................................................................... 125.2.2 Horizontal Chases .................................................................................... 125.2.3 Vertical Chases ......................................................................................... 125.2.4 Masonry Directly Above A Recess......................................................... 12

5.3

Workmanship .................................................................................................................. 13
5.3.1 Bedding of Masonry Units ...................................................................................13
5.3.2 Bond ........................................................................................................................ 13

6

Special Considerations for Earthquake Resistance ................................................................ 13
6.1
6.2

Siting ................................................................................................................................. 13
General Concepts ............................................................................................................ 13
6.2.1 Categories of Buildings ........................................................................................ 13
6.2.2 Seismic Zoning....................................................................................................... 14
6.2.3 Importance of Building ........................................................................................ 14

7

Site Considerations ..................................................................................................................... 16
7.1
7.2
7.3
7.4
7.5

8

General............................................................................................................................. 16
General Considerations................................................................................................. 16
Site Investigation Requirements .................................................................................. 16
Allowable Bearing Pressure.......................................................................................... 17
Combination of Parameters.......................................................................................... 17

Openings in Walls ....................................................................................................................... 21

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9Masonry Bond ............................................................................................................................. 22
9.1

10

Vertical Joints between Perpendicular Walls ............................................................ 22

Horizontal Reinforcement in Walls.......................................................................................... 23
10.1

Horizontal Bands or Ring Beams ................................................................................ 23

11

Section of Bands or Ring Beams............................................................................................... 25

12

Dowels at Corners and Junctions ............................................................................................. 28

13

Vertical Reinforcement in Walls .............................................................................................. 31

14

Reinforcement Details for Hollow Block Masonry ................................................................ 33
14.1

15

Vertical Reinforcement .............................................................................................................. 34
15.1

16

Horizontal Band ............................................................................................................. 33

Infill Panels and Non Structural Walls............................................. ........................ 34

Wall Thickness and Spacing......................................................................................................36

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0.

Foreword

0.1

Design Aspect Covered
This Code of Practice covers the structural design aspect of unreinforced masonry elements inthe buildings. It also deals with some aspect of earthquake-resistant design of buildings.
References to seismic zoning, seismic coefficients, important factors, structural performancefactors and performance coefficient are as per NBC 105-94 Seismic Design of Buildings in
Nepal.

0.2

Related Codes
This Code should be read in conjunction with the Indian Standard IS:1905-1987 Code ofPractice for Structural Use of Unreinforced Masonry (Third Revision).

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1

Scope
1.1

CoverageThis is a Code of Practice for the Structural Design Aspects of Unreinforced Masonry
Buildings in Nepal.

1.2

Limitation
The recommendations of this Code of Practice do not cover walls constructed in mud
mortar and should not be used for such case.

1.3

Provisions for Historical Buildings
The provisions of this Code of Practice shall be construed as advisory when being
applied to the repair, alternations or additions necessary for the conservation,
preservation, restoration, rehabilitation, reconstruction or continued use of buildings ofhistorical, architectural, cultural or archaeological significance.

2

Interpretation
2.1

GeneralIn this Code of Practice the word "shall" indicates a requirement that is to be adopted inorder to comply with the Code of Practice, while the word "should" indicatesrecommended practice.

2.2

Terminology
BEDDED AREA means the area of surface of a masonry unit which is in contact withmortar in the plane of joint.
CORBEL means one or more courses of brick projecting from a wall (such as acornice), generally to form a support for wall plates, etc. A brick should not project
more than one quarter of its length beyond the next lower course.
DEFINITIONS : The terminoloty given in Indian Standard IS:1905-1987 in clauses
2.1 to 2.21.3 will apply, except as stated here below.
DIMENSION means the measured dimension of a designed item and, if used todescribe masonry units, means the nominal dimension.
INFILL PANEL means a wall framed on four sides by columns and beams andcontributing to shear resistance in the plane of the frame, but which is not designed toresist vertical loads other than its own weight.

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LATERAL SUPPORT means a masonry structure support which enables a masonryelement to resist lateral load and/or restrains the deflection of the masonry element at
the point of support.
MASONRY means an arrangement of masonry units which may be brick,rectangularised stone, ashlar or cement blocks laid to a bond and joined together withmortar.
MASONRY UNIT means an individual unit which is bonded to similar units with thehelp of mortar to form a masonry element such as a wall, column, pier, buttress, etc.,
and conforming to the Nepal Standard Brick Masonry NS: 1/2035.
PANEL WALL means an exterior non load-bearing wall in framed construction
wholly supported by beams and columns.
PARTITION WALL means an interior non load-bearing wall which is separated so as
not to be part of the seismic resisting structure.
PARTY WALL means a wall built on land belonging to two adjoining owners, it
being the joint property of both the owners.
SLENDERNESS RATIO means the ratio of effective height or effective length to theeffective thickness which ever is less.
SR

2.3

=

Slenderness Ratio=

Effective Height orEffective Thickness

Effective Length
Effective Thickness

Symbols
The following letters, symbols and abbreviation are used for the purposes of thissection and other symbols are specified at their respective places.

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AArea of sectionb

Breadth of masonry unit or shorter dimension of a rectangular column

DL

Dead loadE

Modulus of elasticityeEccentricity

fb

Basic compressive stressfc

Permissible compressive stressfdCompressive stress due to dead load

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3

fs

Permissible shear stressK

Stiffness of memberkaArea factor

kp

Shape modification factor

ks

Stress reduction factor

LL

Live loadlAxial load on a compression member

lefEffective length or spanmModular ratio

W

Total load

WL

Wind loadw

Uniform distributed load

wp

Breadth of crosswall, piers, or buttresses

Z

Modulus of section

Materials
3.1

Permissible Material
The materials used in masonry construction shall be in accordance with NBC 101-94
Marerial Specifications unless otherwise specified.

3.2

Masonry Unit
The specification and properties of the masonry shall conform to the Nepal Standard
Brick Masonry NS: 1/2035. Its size is given below :NBC109V1.RV7

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Dimensions of Nepal Standard Brick (mm)LengthBreadthHeightVerticalMortar Joint

Remark

240

115

57

10

For 10 mm mortar joint

Table 3.1 : Dimensions of a Nepal Standard Birck
Note : Length of Birck = 2 x Width of Birck + 1 Vertical Mortar Joint
3.3

Tolerances
Tolerance for First and Second Class bricks are as in given Tables 3.2. and 3.3

Individual Brick Size
(Nominal Dimensions) (mm)Length of 20 Bricks
(mm)

Class

LengthBreadthHeightMinimum

Maximum

A
A
A

240
-

115
-

57

4700
2240
1170

4860
2360
1270

Table 3.2 :Individual Brick Size And Length of 20 Bricks (Class A)

Individual Brick Size
(Nominal Dimensions) (mm)Class

LengthBreadthHeightMinimum

Maximum

B
B
B

240
-

115
-

57

4660
2200
1150

4880
2360
1270

Table 3.3 :NBC109V1.RV7

Length of 20 Bricks(mm)Individual Brick Size and Length of 20 Bricks (Class B)

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3.4

Classification of Bricks and Brickwork
3.4.1

First Class Brickwork
All the bricks used for masonry construction shall be thoroughly burnt, deepcherry red or copper in colour, regular in standard shape and size, free fromcracks, emit a clear ringing sound on tapping with a steel trowel and have acrushing strength as per the Nepal Standard Brick Masonry NS: 1/2035. A
brick shall not absorb more water than 15 % of its weight after 24 hours ofsoaking in water at normal temperatures. However, hand-made bricks withkeys may have water absorption up to 25 % of their weight. For first classbrickwork, the corresponding mortar types should be H1 and H2.

3.4.2

Limitation
Masonry units that have been previously used should not be re-used in brickwork or brickwork construction unless they have been thoroughly cleaned andshown to conform to the Nepal Standard Brick Masonry NS: 1/2035.

3.5

MortarMortar used in masonry construction shall, unless otherwise specified, conform to thespecification listed in NBC 101 – Material Specifications.
Some of the commonly-used mortars in Nepal and their mix proportions, along with
their strengths, are listed in Table 3.4.

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SerialNo.

*

Mix(by volume)

MinimumCompressive
Strength at
28 days(N/mm2)*MortarType

Cement

Lime

Sand

1

1

0 to 0.25 C

3

10.0

H1

2(a)
2(b)

1
1

0
0.5 C

4
4.5

7.5
6.0

H2
H2

3(a)
3(b)

1
1

0
1C

5
6

5.0
3.0

M1
M1

4(a)
4(b)
4(c)

1
1
0

0
2C
1A

6
9
2 to 3

3.0
2.0
2.0

M2
M2
M2

5(a)
5(b)

1
1

0
3C

8
12

0.7
0.7

L1
L1

6

0

1 B or C

2 to 3

0.5

L2

1 N/mm2 = 1 MPa = 10.2 kg/cm2

Table 3.4 : Mix Proportions and Strength of Commonly- Used Mortars for
Masonry
Notes :i)

The strength of mortar may vary appreciably depending on the angularity, grading andfineness of the sand. The quantity of sand in the mix may, therefore, be decreased
where found necessary to attain the desired strength.

ii)

A, B and C denote eminently hydraulic lime, semi-hydraulic lime and fat lime
respectively.

iii)

When using plain cement sand mortars [S. No. 2(a), 3(a), 4(a), and 5(a)], it is desirable
to include a plasticizer in the mix to improve workability.

iv)

For mortar to S. No. 6, if lime C is used, part of the sand should be replaced by some
pozzolanic materials (eg., burnt clay or fly ash), in order to obtain the requiredcompressive stress.

v)

In this table, the classification of mortars as types H1, H2, M1, M2, L1 or L2 has been
given for convenience of reference in design calculations, the letter H standing for highstrength, M for medium strength and L for low strength.

vi)

For mortar types H2, M1, and M2, although the compressive strength of composite

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mortars (that is, cement and lime mortars) is somewhat less than that of cement
mortars, the masonry strength may not be significantly affected.
4

General Construction and Design Requirements
4.1

GeneralThe porvisions in clause 4.1 to 4.7 of the Indian Standard IS:1905-1987 shall beapplicable for designing masonry structures. In addition, the following clauses will
also be equally applicable :4.2

Selection of Mortar
The requirements of a good mortar for masonry structure are workability, strength,water retentively and low drying shrinkage. Mortar strength in general should not begreater than that of the masonry unit. For commonly-used mortars conforming toTable 3.4, the optimum mortar mixes from a brick strength consideration are given in
Table 4.1.

Table 4.1 :4.3

Mortar Typebelow 5M2

5 to 14.9

M1

15 to 24.9

H2

25 or above

H1

Optimum Mortar Mixes For Maximum Masonry Strength with
Masonry Units of Various Strengths

Thickness of Wallsa)

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Masonry Unit Strength(N/mm2)The thickness of a load-bearing wall shall be sufficient at all points to ensurethat stresses due to the worst condition of loading for which the wall is designed
are within the safe limit. The thickness of non load-bearing walls shall be
sufficient to meet considerations of stability and strength against lateral forces.

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4.4

b)

The thickness used for design calculation shall be the actual thickness of themasonry, not the nominal thickness. The actual thickness shall be computed as
the sum of the average dimensions of the masonry units as specified in the
Nepal Standard Brick Masonry NS:1/2035, together with the specified joint
thickness. In masonry with raked joints, the thickness shall be reduced by thedepth of raking. However, if joints are raked to provide a key for subsequent
plastering and the mix of mortar for plastering is not weaker than the masonrymortar, raking may be ignored. Also, if the raking of joints is to be followedby flush-pointing using a mortar of the same or better strength, the raking may
be ignored.

c)

The thickness of a wall determined from strength considerations may not be
always sufficient to satisfy requirements with regard to other properties of thewall such as resistance to fire, thermal insulation, sound insulation or resistanceto rain penetration.

Stability Requirements
4.4.1

Lateral Support
Lateral support for a masonry element such as a wall or column is required:

4.4.2

a)

to resist horizontal components of the forces so as to ensure stability ofthe structure against over-turning; andb)to limit the slenderness of masonry elements in order to prevent failure
by buckling.

Adequate Lateral Support
A wall or column may be considered to be provided with adequate lateralsupport if the construction providing the support is capable of resisting thegreater of the following lateral forces :a)

The simple static reactions at the point of lateral support to the total
applied horizontal forces ; or 2.5 percent of the total vertical load thatthe wall or column is designed to carry at the point of lateral support.

Lateral support may be provided in either the vertical or horizontal direction.
Horizontal lateral support could consist of the floor/roof acting as a horizontal
girder capable of transmitting without excessive stresses the horizontal forces tocross-walls acting as stiffening walls. Vertical support could consist of
cross-walls/piers/buttresses capable of transmitting without excessive stresses
the horizontal forces to the foundation.

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4.5

Parapets and Compound Walls
4.5.1

GeneralSince, in the case of a free-standing wall such as a compound wall or parapet
wall, there is no lateral support at its top and no cross-walls to brace the same,stability shall be achieved by designing the wall as a gravity structure such thatthe factor of safety against overturning is at least 1.5. As straight walls
designed on this basis tend to be heavy, the stability of free-standing walls
greater than 0.9 m in height should be achieved by staggering or by theprovision of piers or buttresses. Even though a straight free-standing wall may
be stable with the stipulated factor of safety (1.5), it will have some tension,
because a condition of zero tension corresponds to a factor of safety of 3 against
overturning. Mortar used in masonry of a straight, free-standing wall should
not normally be weaker than type M1 indicated in Table 4.1 unless walls are
thick enough in relation to their height so as to be free from any tension.

4.5.2

Free-Standing Walls
A free-standing wall must be designed to be safe as a vertical cantilever. All
partition walls inside a building must be held on their sides as well as at their
tops.

4.5.3

Load Bearing Masonry Elements
In the case of an unreinforced load-bearing wall using ordinary Portland
cement, the slenderness ratio shall not exceed 17.

4.5.4

Slenderness Ratio
The slenderness ratio for a load-bearing column shall not exceed 12.

4.5.5

Curtain Walls
Curtain walls shall be designed as panel walls to resist lateral forces caused bywind or earthquakes in addition to their own weight. The junction details at thelateral supports shall be such that any vertical deformations or rotations of thestructural members providing the lateral support are not transferred to thecurtain wall. Similarly, there shall be freedom for the curtain wall to have
deformation in the vertical direction.

4.6

Structural Design
The specificaton laid down in clauses 5.1 to 5.5.5 of Indian Standard IS:1905-1987
shall apply to the structural design of masonry. The additional clauses as given here
under shall also apply.

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4.7

Design Method
The structural design of non-reinforced masonry shall be as per the design procedures
given below :4.7.1

Design Procedures
The building as a whole shall be analysed by accepted principle of mechanics toensure the safe and proper functioning in service of its component parts relative
to the whole building. All component parts of the structure shall be capable ofsustaining the most adverse combinations of loads to which the building may bereasonably expected to be subjected during or after erection.

4.7.2

Design Loads
Loads to be taken into consideration for designing masonry components of astructure are :

4.7.3

a)

dead load of walls, column, floors and roofs;b)live load on floors and roof;c)wind load on walls and roof; andd)seismic forces.

Design of Wall Footings
4.7.3.1 Depth of Footing
The net safe bearing capacity of the soil and the depth of foundation in
the soil are best determined by modern soil investigation methods. In
the absence of such an investigation report, a conservative minimum
depth of footing may be determined using the following formula :P
1 − Sinλ
1 + Sinλ

D=

2

W
where :
D = minimum depth of footing in metres.
P = net safe bearing capacity of soil (kPa).
W = unit weight of soil (kN/m3).
λ = angle of repose of soil in degrees.
Note :

NBC109V1.RV7

The above formula is not valid if the soil condition is Soft or
Weak as categorised in Table 7.1. In all

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cases, the footing should be founded below seasonal moisturevariation and to consistent bearing

4.7.3.2 Width of Footing
The minimum width of the footing, B, shall be obtained by dividing thetotal load (including dead loads), live and wind load) by the allowablebearing capacity of the soil :TB=P
where :

B = width of footing in metres.
T = total load per metre.
P = safe bearing capacity.
Note :

4.7.4

The above formula is not valid if the soil condition is Soft or
Weak as categorised in Table 7.1.

Permissible Compressive Stresses
The permissible compressive stresses shall be in accordance with the IndianStandard IS : 1905-1987 in which the design value of permissible compressive
stress, fc , depends on a combination of the following factors :1)

basic compressive stress based on type and strength of the masonryunits and mix of mortar, fb

2)factor for slenderness ratio and eccentricity of masonry elements, kse

3)factor for shape and size of the masonry unit, kp

4)

factor for cross-sectional area of masonry, ka and5)factor for load type, kl

so that :fc= fb kse kp ka kl
The values of the basic compressive stresses and the various factors are given in
IS : 1905-1987, clause 5 and its subclauses.

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5

General Requirements
5.1

Deforming and Cracking
Special provisions shall be made to control or isolate thermal and other movements sothat damage to the fabric of the building is avoided and its structural sufficiency ispreserved. The design and installation of joints shall be done in accordance withaccepted practice.

5.2

Cutting and Chasing
As far as possible, service (Electrical, Plumbing, etc.) should be planned with the helpof vertical chases. Horizontal chases should be avoided.
For load-bearing walls, the depth of vertical chases and horizontal chases shall not
exceed one-third and one-sixth of the thickness of the masonry, respectively.
No chase shall be permitted in a half-brick load-bearing wall.

5.2.1

Stretches of Masonry
When narrow stretches of masonry (or short lengths of wall), such as between
doors and windows, cannot be avoided, they should not be pierced with
openings for soil pipes or waste pipes or timber joists, etc. Where there is apossibility of load concentration, such narrow lengths of walls shall be checked
for stresses and high-strength bricks/mortar or concrete walls provided, if
required.

5.2.2

Horizontal Chases
Horizontal chases, when unavoidable, shall be located in the upper or lower
thirds of a storey and not more than three chases should be permitted in any
stretch of a wall. No continuous horizontal chase shall exceed one metre in
length.

5.2.3

Vertical Chases
Vertical chases shall not be closer than two metres in any stretch of a wall.
These shall be kept away from the bearing of beams and lintels. If unavoidable,
stresses in the affected area should be checked and kept within permissible
limits.

5.2.4

Masonry Directly Above A Recess
Masonry directly above a recess, if wider than 30 cm (horizontal dimension),should be supported on lintel. Holes in masonry up to 30 cm width x 30 cm
high may be provided without a lintel. In the case of circular holes in masonry,a lintel should be provided only if arch action can not be achieved.

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5.3

WorkmanshipThe quality of workmanship has considerable effect on the strength of masonry and badworkmanship may reduce the strength of brick masonry to as low as half the intended
strength. The basic compressive stress values for masonry given in IS : 1905-1987,
Table 8 are appropriate for commercially-obtainable standards of workmanship with areasonable degree of supervision. If the work is going to be inadequately supervised,
design strengths should be reduced to three-quarters of these values.

5.3.1

Bedding of Masonry Units
Masonry units shall be laid on a full bed of mortar with the frog, if any, upward
and so that cross-joints and bed-joints are completely filled with mortar.
Masonry units which are moved after their initial placement shall be re-laid infresh mortar. Old or disturbed mortar shall be discarded.

5.3.2

Bond
The cross-joints in any course of one brick thick masonry walls shall be not lessthan one quarter of a masonry unit in horizontal measurement from thecross-joints in the course below. In masonry walls more than one brick inthickness, bonding through the thickness of the wall shall be provided by either
header units or by other equivalent means.

6Special Considerations for Earthquake Resistance
6.1

Siting
The site should be free from landslide and rock fall areas and liquefaction potential(loose, saturated sand up to about six metres depth below the ground surface). See
NBC 108-94 Site Considerations for more details.

6.2

General Concepts
6.2.1

Categories of Buildings
For categorizing buildings for the purpose of achieving seismic resistance ateconomical cost, three parameters turn out to be significant :a)

Seismic Intensity Zoning where the building is located,b)

Important of the building andc)

Stiffness of the foundation soil.

A combination of these parameters will determine the extent of appropriate
seismic strengthening of the building.

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14

6.2.2

Seismic Zoning
The variation in seismic hazard with location in Nepal is defined for design
purposes in Figure 8.2 of NBC105-94 Seismic Design of Buildings in Nepal.
For the purpose of the design of unreinforced masonry, a simplified zonation
based on this figure shall be used.
Three zones A, B and C are defined in Table 6.1 and are shown in Figure 6.1
below.
Zone

Zone CoefficientA

Z ≥ 1.0B

0.8 ≥ Z > 1.0

Moderate Damage

C

Z < 0.8

Minor Damage

Table 6.1 :
6.2.3

Risk
Widespread Collapse and Heavy Damage

Seismic Zones for Unreinforced Masonry

Importance of Building
The importance of the building should be a factor in grading it for strengthening
purposes. Importance depends upon its occupancy, use and need before andafter a disaster as given in Table 6.2.

0.8

Zone A

Zone C

0.8

Zone B

0.9

1.0
1.0
0.8

Kathmandu

Zone B
Zone C

0.9

Zone A

Figure 1.1: Seismic Zoning Map of Nepal for this MRT

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15

Occupancy Category

Occupancy Type or Function of Structure

IMPORTANT CATEGORY
Hospital and other medical facilities

1. Essential Facilities

Fire and Police Station
Tanks or other structures containing, housing or
supporting water or other fire-suppression material or
equipment required for the protection of essential or
hazardous facilities.
Emergency vehicle shelter and garage
Structures and equipment in emergency-preparedness
centres and relief stores.
Power stations and standby power-generating
equipment for essential facilities
Structures and equipment in communication centres eg.
radio, television facility, telephone exchange etc.
Food storage structures
Offices and quarters for personnel related to central anddistrict level rescue and relief operations eg. ministers,
secretaries, police and army chiefs, CDO, LDO, DDC
chairman, district level army and police chiefs
2. Places of Assembly

Schools, colleges, hostels
cinema hall, culture, covered hall convention halls,
temples, dharmashalas

3. Monumental Buildings

Historic buildings, palaces

4. Distribution Facilities

Gas or petroleum products in urban areas

5. Hazardous Facilities

Structures housing, supporting or containing sufficientquantities of toxic or explosive substances to be
dangerous to the safety of the general public if release

ORDINARY CATEGORY
6. Ordinary Occupancy
Structures

Table 6.2 :NBC109V1.RV7

Any structure / building not described above eg
residential, offices, etc.

Occupancy Category

19 May 1994

16

The buildings under the Important category have been subdivided into two groups from a
constructions point of view. These are :7

A.

Buildings in accessible areas where modern materials such as cement and reinforcing
bars can be easily transported

B.

Buildings in remote inaccessible areas to where modern materials can not easily betransported.

Site Considerations
7.1

GeneralThis section sets out some of the requirements to be considered during site selection forthe construction of buildings in order to minimise the risks to buildings from bothprimary geological hazards and secondary seismic hazards such as fault rupture,landslide and liquefaction. Since this is the first such effort to introduce the importanceof geotechnical conditions and the nature of foundation soil in the stability of Nepalesebuilding, the requirements set out here have deliberately been kept low to encourage
effective implementation.

7.2

General Considerations
As a good practice during the construction of a building, it is necessary to examine all
existing local knowledge and the performance histories of existing building. The
designer should thus be able to identify any dangers from an inherent naturalsusceptibility of the land to the processes of sliding, erosion, land subsidence andliquefaction during past earthquakes, or from any other natural/geological process
likely to threaten the integrity of the building. The local practice of managing suchhazards, if any, should be judged against the required level of acceptable risk.

7.3

Site Investigation Requirements
For load-bearing masonry buildings and reinforced concrete (RC) frame buildings withmasonry infills, site exploration should be carried out by digging test pits, two as aminimum, and more if the subsurface soil conditions show a variation in soil types.
Generally the depth of exploration for the buildings should be a minimum of two
metres. In hilly areas, exploration up to the depth of sound bed rock, if it lies shallower
than two metres, should suffice.
No exploration shall be required if the site is located on rock or on fluvial terraces (Tar)with boulder beds.

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17

The soils encountered in the test pits should be classified as per Table 7.1.

7.4

Allowable Bearing Pressure
The allowable bearing pressure could be calculated using the Table 7.1. in conjunction
with the visual classification of the subsurface soil type.

Foundation
Classification

Presumed Safe
Bearing
Capacity(kN/m2)Rocks in different state of weathering;boulder beds; gravel; sandy gravel and sandgravel mixtures; dense or loose coarse to
medium sand; offering high resistance topenetration when excavated by tools; stiff tomedium clay which is readily indented with athumb nail.

Hard

≥ 200

Fine sand and silt (dry lumps easily
pulverised by the finger); moist clay andsand-clay mixtures which can be indented
with strong thumb pressure.

Medium≥ 150 and < 200

Fine sand; loose and dry; soft clay indented
with moderate thumb pressure.

Soft≥ 100 and < 150

Very soft clay which can be penetrated
several centimetres with the thumb; wet clays.

Weak

≥50

Type of Soil/Rock

Table 7.1 :Classification of Foundaton Soil And Safe Bearing Capacity

Buildings can be constructed on hard, medium and soft soils but it will be dangerous tobuild them on weak soils. Hence, appropriate soil investigation should be carried out toestablish the allowable bearing capacity and nature of soils. Weak soils must be
avoided or compacted to improve them so that they qualify as at least Medium or Softsoils.

7.5

Combination of Parameters
For determining the categories of building for seismic strengthening purposes four
categories (I to IV) are defined in Table 7.2 in which category I will require maximum
strengthening and category IV the least. The general planning and designing principles
are, however, equally applicable to all categories.

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18

Category

Combination of Conditions for the Category

I

Important Building on Soft Soil in Zone A

II

Important Building on Firm Soil in Zone A
Important Building on Soft Soil in Zone B
Ordinary Building on Firm Soil in Zone A

III

Important Building on Firm Soil in Zone B
Important Building on Soft Soil in Zone C
Ordinary Building on Firm Soil in Zone A
Ordinary Building on Soft Soil in Zone B

IV

Important Building on Firm Soil in Zone C
Ordinary Building on Firm Soil in Zone B
Ordinary Building on Firm Soil in Zone C
Ordinary Building on Soft Soil in Zone C

Table 7.2 : Categories of Buildings for Strengthening Purposes
Notes :

NBC109V1.RV7

i)Seismic Zones A, B and C are as per Figure 6.1

ii)

Weak soils liable to compaction and liquefaction under earthquake conditions
are not covered here.

19 May 1994

19

Crosswal

L1

L2

h1

b5

b7

b6

h2

b3

h2

b2

b1

h3

b9

b4

b4

b4

b4

Note:
i)

b1+b2+b3<0.5 L1 for one storey,<0.42 L1 for two-storeyed,<0.33 L1 for three-storeyed

ii)

b6+b7

<0.5 L1 for one storey,<0.42 L1 for two-storeyed,<0.33 L1 for three-storeyed

iii)

b4

>0.5 h, but not less than 600 mm

iv)

b5

>0.25 h, but not less than 600 mmv)

b3> 600 mm and > 0.5 (bigger of b2 and b9)

Figure 7.1 : Recommendations Regarding Opeinings in Bearing Walls

NBC109V1.RV7

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20

ALTERNATIVE - 1

ALTERNATIVE - 2

V = 2, ØV = 1, Ø

SECTIONAL PLAN AT Y - Y

40d

40d

40d

40d

t1

Lintel band

W

W

t1

t1

or

V

V

SECTION AT X - X

1/2 L

3/4 L

L

25

1/2 L

V

V

2nd COURSE

1st COURSE∅ -- Diameter,

W -- Window,

V --- Vertical Reinforcing bar,t -- Thickness of wall ( minimu l brick length) ,t1 -- Minimum thickness 75 mm.,

L -- Length of brick unit.

Figure 7.2 : Strengthening of Masonry Around Openings

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21

8

Openings in Wallsa)Openings shall be located away from the inside corner by a clear distance equal to atleast one-quarter of the height of openings, but not less than 600 mm.

b)

The total length of openings shall not exceed 50 % of the length of the wall between
consecutive cross-walls in single-storey construction, 42 % in two-storey construction
and 33 % in three-storey buildings.

c)

The horizontal distance (pier width) between two openings shall not be less than onehalf of the height of the shorter opening (Figure 7.1), but not less than 600 mm.

d)

The vertical distance from an opening to an opening directly above it shall not be lessthan 600 mm, nor less than one-half of the width of the smaller opening (Figure 7.1)e)When openings do not comply with requirements (a) to (b), they should be boxed inreinforced jambs through the masonry (Figure 7.2)

f)Tops of openings in a storey should preferably be at the same level, so that acontinuous band which includes the lintels throughout the building can be provided.

g)

If a window or ventilator is to be projected out, the projection shall be in reinforced
masonry or concrete and well-anchored.

h)

If an opening is tall enough with respect to the full height of wall so as to divide
effectively the wall into two portions, these portions shall be reinforced with at least 6
mm diameter horizontal bars at not more than 600 mm intervals on both the inner andouter faces. This steel at jambs and at corners or junctions of walls.

i)

The use of arches to span over the openings is a source of weakness and shall be
avoided unless steel ties are provided.

j)

All the walls must be effectively tied together to avoid separation at vertical joints due
to ground-shaking during an earthquake.

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22

9

Masonry Bond
9.1

Vertical Joints between Perpendicular Walls
A sloped or stepped joint should be made in order to obtain full bond by making thecorners first to a height of 600 mm and then building the wall in between them.
Alternatively, a toothed joint should be made in each wall alternately in lifts of about
450 mm, as shown in Figure 9.1.

230

c

B
c

A

450

b

450

230

450

450

230

c

a
c
b
a

All dimensions are in mm.
a, b, c Toothed joint in walls A, B and C( Alternating toothed joint in walls at corner and T-junctions )Figure 9.1: A Typical Detail of Jointing in Masonry

NBC109V1.RV7

19 May 1994

23

10

Horizontal Reinforcement in Walls
Horizontal reinforcing of walls is required to give to them horizontal bending strength against
plate-action for out-of-plane inertia loads, and for tying orthogonal walls together.

10.1

Horizontal Bands or Ring Beamsa)

Plinth BandA plinth band should be provided in all cases where the soil is soft or uneven inits properties.

b)

Lintel BandThe lintel band shall incorporate all door and window lintels, the reinforcementof which should be extra to the lintel band steel. It must be provided in all
storeys in all walls of the buildings as per Table 11.1.

c)Roof BandA roof band shall be provided at the eave-level of trussed roofs (Figure 4), andalso below or in the level of such floors that consist of joists and covering
elements so as to properly integrate them at their ends and fix them into thewalls.

d)

Gable Band
Masonry gable-ends must have the triangular portion of masonry enclosed in aband, the horizontal part of which will be continuous with the eave-level bandon longitudinal walls (Figure 10.1).

NBC109V1.RV7

19 May 1994

24

G
G

R

R

1

L

2
1

( a)

2500

R

L - Lintel band,( b )DETAIL AT - 1
Note:

R - Roof band
G - Gable band( c ) DETAIL AT - 2( Fixing of roof to wall )i) As an alternative to the gable masonry, a truss or open gable may be used and the openings
covered with a light material such as sheeting, matting etc.
ii) If the wall-height up to eave-level is less than or equal to 2.5 m , the lintel-level band may beommitted and the lintel integrated with the eave-level band as shown in Detail 2.

Figure 10.1 : Gable Band and Roof Band in Barrack-Type Buildings

NBC109V1.RV7

19 May 1994

25

11

Section of Bands or Ring Beams
A band consists of two (or four) longitudinal steel bars with stirrups embedded in 75 mm (or150m mm) thick concrete (Figure 11.1 and 11.2).
The thickness of the band may be made equal to, or a multiple of, a masonry unit, and its width
shall equal the thickness of the wall.
The steel bars shall be located close to the wall faces with 25 mm cover, and full continuity
shall be provided at corners and junctions.

10Øs or 75mm whichever is greater

30

10Øs or 75mm whichever is greater
30

75

150

30

b
b

a) CROSS SECTION OF R.C. BAND FOR TWO BARS AND FOUR BARS OF DIA. '
b1

Ø'

b1

b2

> 150

> 150

b2

b) R. C. BAND REINFORCEMENT DETAILS AT CORNER AND T-JUCTIONb, b1, b2 = Wall thickness
2 strength.
Concrete
1 : 2 : 4 or 15 N/ mm cube

Note:

Provide overlaps for slicing bars outside the corner length of overlap
to develop full band say 50 d.

Figure 11.1 : Reinforced Concrete Band and Details

NBC109V1.RV7

19 May 1994

26

60

60

60

30

75

150

30

30

b

6Ø@150or5b

6Ø@150or5a) CROSSSECTIONOFR.C.C. BANDFORTWOBARSANDFOURBARS
b1

b1

b2

b2

b) R. C. BANDREINFORCEMENTDETAILSATCORNERANDT-JUCTIONb, b1, b2 = Wall thickness
2 strength.
Concrete 1 : 2 : 4or 15 N/ mm cube

Note:

Provideoverlaps for slicing bars outside the corner lengthof overlap
todevelop full band say50d.

Figure 11.2: Reinforcement inReinforcedConcreteBand

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27

Longitudinal steel in Reinforced Concrete (RC) Bands
Span ofwall
between
cross
wall
(m)

Category I
No.
of
Bars

Category II

Bar Dia.
(mm)
T*

K*

No.
of
Bars

Category III

Bar Dia.
(mm)
T

K

No.
of
Bars

Category IV

Bar Dia.
(mm)
T

K

No.
of
Bars

Bar Dia.
(mm)
T

K

5 or
Less

2

10

9

2

10

9

2

10

9

2

10

9

6

2

12

-

2

10

9

2

10

9

2

10

9

7

2

12

-

2

12

-

2

10

9

2

10

9

* T = High strength bar having an fy of 415 N/mm² (Fe 415 Grade)
K = High strength bar having an fy of 550 N/mm² (Fe 550 Grade)

Table 11.1 : Recommendation for Steel in RC Bands
Notes :
i)

Width of the RC band is assumed to be the same as the thickness of wall. Wall thickness
shall be 230 mm minimum. A cover of 25 mm from face of wall shall be maintained.

ii)

The vertical thickness of a RC band may be kept to a minimum of 75 mm where twolongitudinal bars are specified and 150 mm where four longitudinal bars are specified.

iii)

Concrete mix to be 1:2:4 by volume or to have an M15 Grade cube crushing strength
at 28 days.

iv)

The longitudinal bars shall be held in position by steel stirrups 6 mm in diameter
spaced no more than 150 mm apart.

NBC109V1.RV7

19 May 1994

28

12

Dowels at Corners and Junctions
Steel dowel bars shall be used at corners and T-junctions to integrate the box action of walls.
Dowels (Figures 12.1, 12.2, 12.3 and 12.4) are to be taken into the walls to a sufficient length
so as to provide their full bond strength.

t11.20 - 1.50 m

Ø5 - 8 mm
1.20 - 1.50 m

Ø5 - 8 mm

Ø5 - 8 mm

1.20 - 1.50 m

l1.20 - 1.50 m

Ø5 - 8 mm

t2

Ø5 - 8 mm

1

Ø5 - 8 mm

500 - 700 mm

2

500 - 700 mm

2

2

t 1, t 2 = Wall thickness
1= Cross links
2= Thick joints to receive dowels

Figure 12.1 : Corner-Strengthening by Dowel Reinforcement Placed in One Joint

NBC109V1.RV7

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29

t1

1.20 - 1.50m

Ø5 - 8mm
1.20 - 1.50 m

Ø5 - 8mm

1.20 - 1.50m

1.20 - 1.50 m

1

Ø5 - 8mm
Ø5 - 8mmt2

1

Ø5 - 8mm

Ø5 - 8mm22500 - 700 mm

2
2

500 - 700 mm
500 - 700 mm

2
2

t 1, t 2 = Wall thickness
1= Cross links
2= Thick joints to receive dowels

Figure 12.1 : Corner-Strengthening by Dowel Reinforcement Placed in Two Consecutive
Joint

NBC109V1.RV7

19 May 1994

30

t2

1.20 - 1.50 m

l

l

t1

Rods Ø 5 - 8 mm

Ø 5 - 8 mm

1.20 - 1.50 m

1.20 - 1.50 m

t 1, t 2 = Wall thickness,l = Cross links

Figure 12.3 : T-Junction Strengthening by Dowel Reinforcement1

1.20 - 1.50 m

1.20 - 1.50 m

1

2

2

Figure 12.4 : Strengthening by Wire Fabric at Junctions and Corners

NBC109V1.RV7

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31

13

Vertical Reinforcement in Walls
Steel bars shall be installed at the critical sections (i.e. the corners of walls and jambs of doors
right from the foundation concrete) and covered with cement concrete in cavities made aroundthem during masonry construction (Figure 13.1). This concrete mix should be 1:2:4 byvolume or stronger.
The vertical steel at an opening may be stopped by bending it into the lintel band but thevertical steel at corners and junctions of walls must be taken into the floor slab, roof slab, orroof band.

NumberofStoreysStoreyOne

Diameter of mild steel single bar in mm at eachcritical section by Category
Category I

Category II

Category III

12

10

10

Two

Top
Bottom

12
16

10
12

10
12

Three

Top
MiddleBottom

12
16
16

10
12
12

10
10
12

Table 13.1 :Recommendation for Vertical Steel at Critical Sectionsi)

The above vertical reinforcement in walls is valid for up to threestoreyed buildingsii)

Four-storeyed and above load-bearing wall construction may not be
used for categories I and II buildings.

Notes :

NBC109V1.RV7

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32

1

1/2 1/2 1/4 1/2 1/2 1/2

1

1 /2

1 /2 1 /4 1 /2

V

1

1

1/2 1/2

1

V

1 /2

1 /2 1 /2

F I R S T LAYER

1 /2

1

S E C O N D LAYERC OR N E R JU N C TION D ET A ILS F OR O N E B R IC K W A L L FOR
P R O VID IN G V ER TIC A L ST EE L.
1 1 /2
1/2 1/2 1/2 1/2 1/2
1 1/2
1 /2

1 /2

1 /2 1 /2 1 /2V

1/2 1/2 1/2

V

1 /2 1 /2 1 /2

1 1/2

1/2 1/2 1/4 1/2 1/2 1/2 1/2 1/2

1 1 /2

1 /2 1 /2 1 /4 1 /2 1 /2 1 /2 1 /2 1 /2

F I R S T LAYERS E C O N D LAYERC OR N E R JU N C TION D ET A ILS F OR O N E A N D H A L F B R IC K
W A L L F O R P R O V ID IN G VER TIC A L STEEL.

1 1/2

V

1 /2 1 /2 1 /4 1 /2

1 /2 1 /2 1 /2 1 /2

1 /2 1 /2 1 /4 1 /2 1 /2

F I R S T LAYER

1 /2

1 1/2

1/2 1/2 1/2 1/2 1/2 1/2 1/2V

1/2 1/2 1/2 1/41/2 1/2 1/2

1 1 /21 1 /2

1 /2 1 /2 1 /2 1 /2

S E C O N D LAYER

T - JU N C TION D ET A ILS F OR O N E A N D H A L F B R IC K W A LL
F OR P R O VID IN G V ER TIC A L ST EE L.
1

14, 2 , and 1 indic ates:
V - Vertic al Bar

1

4

Brick wid e,

1

2 Brick wid e, 1 B ric k long etc.,

F ig u re 13.1 : V e rtic a l R e in fo rcem ent in W alls

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33

14

Reinforcement Details for Hollow Block Masonry
14.1

Horizontal BandU-shaped blocks should be used for the construction of horizontal bands at various
levels of the storey as per seismic requirements as shown in Figure 4.1.
The amount of horizontal reinforcement shall be taken as 25 % more than that given in
Table 11.1 and provided by using four bars and 6 mm diameter stirrups.

1

2

3

1 - Lintel Band
2 - Roof Band ( only for pitched roofs and under roofs and floor )3 - Vertical steel.

Figure 14.1 : Overall Arrangement of Reinforcing Masonry Buildings

NBC109V1.RV7

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34

15

Vertical Reinforcement
The vertical bars specified in Table 13.1 can be conveniently located inside the cavities of thehollow blocks - one bar in one cavity. Where more than one bar is planned, these can belocated in two or three consecutive cavities as shown in Figures 15.1 and 15.2.

15.1

NBC109V1.RV7

Infill Panels and Non-Structural Wallsa)

In-fill panel walls in a building shall be designed to ensure that they act together
with the frame in full composite action.

b)

The seismic load at each level shall be distributed to the individual wall in
proportion to the product of each wall's thickness and length. This product isrepresentative of the diagonal strut area and thus of the wall's shear stiffness.

c)

Any frame is to be designed to resist all the gravity loads without any assistancefrom the infill walls as these walls may either fail or be very severely damaged
in a large earthquake.

d)

The centre of rigidity of the infill walls (except face wall) shall be as near as
possible to the centre of rigidity of the complete system of walls.

e)

An infill wall shall be so designed that it sustains minimum damage during any
deflection of the supporting structure during an earthquake and shall be
designed to resist all action resulting from in-plane and face loads.

f)

The minimum thickness of an infilled wall shall be the same as that of partition
walls, and its openings should be as small as possible and cover not more than
10 % of the panel area. The preferable location of an opening in a wall is
outside the central two-thirds of the sides and away from the corners. If the
opening must be near the centre of the wall, it shall be bounded by a reinforced
concrete beam 75 mm thick, the other dimension to be equal to thickness ofwall and reinforced with two 10 mm diameter Fe 415 grade bars longitudinallyand 5 mm diameter Fe 550 grade bar link ties .

g)Partition walls shall have a minimum thickness shall have horizontal
reinforcement (one 6 mm diameter bar in each face) in every sixth course ofblockwork.

h)

If the infill wall is constructed in a Category I or II building, the thickness ofinfill wall shall not be less than 230 mm.

19 May 1994

35

30 Ø

30 Ø

Figure 15.1 : Vertical Reinforcement inBlockwork Cavities

Ø

( a)
( b)

Figure 15.2 : Vertical Reinforcement inCavities

NBC109V1.RV7

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36

16

Wall Thickness and Spacing

The minimun thicknesses and maximum spacings of masonry walls shall be as dexcribed inTables 16.1 and 16.2.

*

Height of Wall (m)Length of Wall (m)Thickness of Wall at
Base (Bricks)

1.

Up to 4.5

Any*

1.5

2.

4.5 to 7.5

Any*

1.5

3.

7.5 to 9

Up to 14
Above 14

1.5
2

4.

9 to 12Up to 99 to 14
14 to 18

1.5
2
2.5

5.

12 to 15

Up to 99 to 182
2.5

6.

15 to 18

Up to 99 to 14

2.5
3Provision should be made for expansion/contraction joints.

Table 16.1 :Buildings

Thickness of Walls for Public Buildings, Warehouse and Incustrial

Notes :

NBC109V1.RV7(i)

An additional thickness of one-half a brick at the base will usually be
sufficient where vibrating machinery is used.

(ii)

The base thickness is reduced towards the top; for 5 m from the top ofwall, the thickness should be 1.5 bricks, but where the wall does notexceed 9 m in height, the wall for 3.5 m from the top may be one brickthick if the wall is in a cement mortar.

19 May 1994

37

Thicknessof LoadBearing
Wall to be
Stiffened(mm)

Height* ofStorey not
to exceed(m)

Stiffening Wall*
Thickness not less than(mm)

1 to 3storeysMax.
Spacing(m)

4 to 6
storeys

1.
100
3.2
240
4.5
2.
240
3.2
360
480
6.0
*
Storey height and maximum spacing are given as centre-to-centre dimensions.

Table 16.2 :NBC109V1.RV7

Thickness and Spacing of Stiffening Walls

19 May 1994