FINAL DRAFT UGANDA 
STANDARD  
  FDUS 2225  
First  Edition  
2020 -mm-dd 
 
 Reference number  
FDUS 2225: 2020 
© UNBS 2020   
  
Expanded polystyrene c ap vaults and c offers — Specifications  
 FDUS  2225 : 2020  
ii © UNBS 2020  – All rights reserved  
 Compliance with this standard does not, of itself confer immunity from legal obligations  
A Uganda Standard does not purport to include all necessary provisions of a contr act. Users are 
responsible for its correct application  
© UNBS 2020   
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permission from UNBS.  
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The Executive Director  
Uganda National Bureau of Standards  
P.O. Box 6329  
Kampala  
Uganda  
Tel: +256 417 333 2 50/1/2 
Fax: +256 41 4 286 123  
E-mail: info@unbs.go.ug  
Web: www.unbs.go.ug  FDUS 2225:  2020  
© UNBS 2020  – All rights reserved  iii 
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ............................  iii 
1 Scope  ................................ ................................ ................................ ................................ ......................  1 
2 Normative references  ................................ ................................ ................................ ............................  1 
3 Terms and definitions  ................................ ................................ ................................ ...........................  1 
4 Symbols and abbreviations  ................................ ................................ ................................ ..................  1 
5 Classification for cap vaults and coffers  ................................ ................................ ............................  2 
6 Requirements for cap  vaults and coffers ................................ ................................ ............................  2 
6.1 General requirements  ................................ ................................ ................................ ...........................  2 
6.1.1  Composition  ................................ ................................ ................................ ................................ ...........  2 
6.1.2 Finishing  ................................ ................................ ................................ ................................ .................  2 
6.2 Physical and mechanical requirements  ................................ ................................ ..............................  2 
6.3 Geometric requirements  ................................ ................................ ................................ .......................  2 
7 Quality system  ................................ ................................ ................................ ................................ ....... 4 
7.1 General  ................................ ................................ ................................ ................................ ...................  4 
7.2 Tests for acceptance  ................................ ................................ ................................ .............................  4 
7.3 Sampling plans  ................................ ................................ ................................ ................................ ...... 5 
8 Labelling  ................................ ................................ ................................ ................................ .................  5 
9 Handling , shipping, and storage  ................................ ................................ ................................ ..........  5 
9.1 Handling  ................................ ................................ ................................ ................................ .................  5 
9.2 Shipping  ................................ ................................ ................................ ................................ .................  5 
9.3 Storage  ................................ ................................ ................................ ................................ ...................  5 
10 Delivery  ................................ ................................ ................................ ................................ ...................  6 
Annex  A (informative)  ................................ ................................ ................................ ................................ ........  7 
A.1 Acceptance inspection  ................................ ................................ ................................ .........................  7 
A.2 Sampling plans  ................................ ................................ ................................ ................................ ...... 7 
Annex  B (normative)  Mechanical properties  ................................ ................................ ................................ .. 8 
B.1 Minimum compression strength test with 10 % deformation  ................................ ...........................  8 
B.1.1  Equipment  ................................ ................................ ................................ ................................ ..............  8 
B.1.2  Sample preparation  ................................ ................................ ................................ ...............................  8 
B.1.3  Calculation  ................................ ................................ ................................ ................................ .............  8 
B.2 Minimum flexural strength test  ................................ ................................ ................................ ............  9 
B.2.1  Equipment  ................................ ................................ ................................ ................................ ..............  9 
B.2.2  Sample preparation  ................................ ................................ ................................ ...............................  9 
B.2.3  Procedure  ................................ ................................ ................................ ................................ ...............  9 
B.2.4  Calculation  ................................ ................................ ................................ ................................ ...........  10 
Annex  C (normative)  Determination of density  ................................ ................................ ............................  11 
C.1 Equipment  ................................ ................................ ................................ ................................ ............  11 
C.2 Sample preparation  ................................ ................................ ................................ .............................  11 
C.3 Calculation  ................................ ................................ ................................ ................................ ...........  11 
Bibliography  ................................ ................................ ................................ ................................ ......................  12 
 
Foreword  FDUS  2225 : 2020  
iv © UNBS 2020  – All rights reserved  
 Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry of Trade , Industry and 
Cooperatives established under Cap 327 , of the Laws of Uganda , as amended .  UNBS is mandated to co -
ordinate the elaboration of standards and is  
(a) a member of International Organisation for Standardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex Alimentarius Commission on Food Standards, an d  
(c) the National Enquiry Point on TBT  Agreement  of the World Trade Organisation (WTO).  
The work of preparing Uganda Standards is carried out through Technical Committees. A Technical 
Committee is established to deliberate on standards in a given field or ar ea and consists of key stakeholders 
including government, academia, consumer groups, private sector and other interested parties.  
Draft Uganda Standards adopted by the Technical Committee are widely circulated to stakeholders and the 
general public for co mments. The committee reviews the comments before recommending the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council.  
The committee responsible for this document is Technical Committee UNBS /TC 03, Building a nd construction . 
 FINAL DRAFT UGANDA STANDARD  FDUS 2225: 2020  
 
© UNBS 2020  – All rights reserved  1 
 Expanded polystyrene cap vaults and coffers — Specifications   
1 Scope  
This Final Draft Uganda Standard specifies requirements , sampling and test methods  for expanded 
polystyrene cap vaults and coffers used as a lost formwork for slabs  in intermediate floors and roofs in 
combination with prefabricated concrete joists with inverted (T) shaped section (
 ). 
2 Normative references  
The following  referenced documents 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 docu ment (including any amendments) applies.  
ISO 2859 -1, Sampling procedures for inspection by attributes — Introduction to the ISO 2859 series of 
standards for sampling for inspection by attributes  
3 Terms and definitions  
For the purposes of this docu ment, the following terms and definitions apply.  
ISO and IEC maintain terminological databases for use in standardization at the following addresses:  
— ISO Online browsing platform: available at http://www.iso.org/ob p 
3.1  
cap vaults of expanded polystyrene  
expanded polystyrene element with a flat and polygonal front section that is used in the works as lost 
formwork supported on joists , hence forth, “vault ” 
3.2  
expanded polystyrene coffer  
produc t that is used in construction as a lost formwork element, which replaces wooden and plastic coffer, 
providing greater lightness. Its shape is rectangular and its dimensions vary according to the project, 
hence forth, “coffer” . 
4 Symbols and ab breviations  
 A Distance between the joist’s axes  
 H Total height of the cap vault in millimet res 
 L Length of the vault  
 A1 Width of the lower section of the vault in millimet res  
2 © UNBS 2020  – All rights reserved  
  A2 and A3   Intermediate widths of the vault in millimeters  
 H1, H2, H3 and H4 Intermediate heights of the vault in millimeters  
5 Classification for cap vaults and coffers  
The cap vaults and coffers  shall be  classified by category accord ing to density .  
6 Requirements for cap vaults and coffers  
6.1 General requirements  
6.1.1 Composition  
The vaults and coffers are made of expanded polystyrene of a predetermined density.  
6.1.2 Finishing  
The vault s and the coffer s shall have a regular  surface, with no protuberances or cavities, and in fulfillment 
with the requirements of the project.  
6.2 Physical and mechanical requirements  
Vaults and coffers shall comply with the requirements  given  in Table 1  when tested in accordance with the test 
methods specified therein . 
Table 1 — Physical and mechanical  requirements  for cap vaults and  coffers  
Property  Requirement  Test method  
Nominal density , kg/m3 10 15 20 25 30  
Density range , kg/m3 9.0 - 13.4 13.5 - 17.9 18.0 - 22.4 22.5 - 26.9 ≥27 Annex C  
Minimum compression 
strength with deformation 
at 10  %, kPa - 65 100 140 180 Annex B 
Minimum f lexural 
strength , kPa 50 160 240 325 410 Annex B  
 
6.3 Geometric requirements   
6.3.1  The typical sample nominal dimensions for the vaults  are given in Table 2.  FDUS  2225: 2020 
© UNBS 2020  – All rights reserved  3 
 Table 2 — Nominal dimensions  for vaults  
Vault 
Height H1 H2 H3 H4 Type of 
joist A1 A2 A3 Distance 
between 
the joist’s 
axis L 
mm mm 
170120
 30 10 25 
10555
 Prestressed  
785585
 
825625  20 
900700
 1 000  
170120
 45 0 28 
9747
 Reinforced  
780580
 
830630  25 
900700
 1 000  
NOTE  Shapes and dimensions other than the nominal ones can be established according to the requirements of the 
project.  
 
6.3.2  The tolerance in the coffer’s dimension are ±5 mm.  The dimension  tolerances of the vaults are  given  
in Table 3.  
Table 3 — Tolerance of the vaults  
Dimension  Tolerance  
Length ( L) ±5 mm  
Width ( A2) ±5 mm  
Height ( H) ±3 mm  
Step Height ( H1) ±2 mm  
Quadrature  3 mm/m  
 
 
Figure 1 — Cap vault   
4 © UNBS 2020  – All rights reserved  
  
 
Figure 2 — Cap vault  
 
 
Figure 3 — Coffer  
7 Quality system  
7.1 General  
In order to ensure the conformity of the product with this standard, an effective and documented quality 
system shall be established and maintained.  
7.2 Tests for acceptance  
7.2.1  The limit for e ach specificat ion shall be evaluated according to the established Acceptable Quality 
Limit  (AQL) , which shall guarantee that this product meets the requirements for quality. The results obtained in 
the acceptance tests performed to the product shall be in acc ordance with the requirements established in 
standard FDUS 2224  
7.2.2 Acceptance tests  shall include the following:  FDUS  2225: 2020 
© UNBS 2020  – All rights reserved  5 
 a) minimum compression strength with 10 % deformation (according to Annex B) ; and  
b) density (according to Annex C). 
7.2.3  Discretiona ry tests  shall include minimum flexural strength (according to Annex B) . 
Table 4 — Sampling plan  
Density  
Minimum flexural strength  
Minimum compressive strength with 10% deformation  ISO 2859 -1  
Inspection by variables  
AQL 4.0  % 
Level S - 3  
Norm al inspection  
 
7.3 Sampling plans  
For preparation of the sampling plans shown in Table 4 and their statistical interpretation in Annex A 
(normative) of this standard .  
8 Labelling  
Each commercial batch of vaults and coffers shall be legibly  and indelibly  marked with the following 
information:  
a) manufacturer  identification ; 
b) date of manufacture ; 
c) classification and class type . 
9 Handling , shipping, an d storage  
9.1 Handling  
Handling of  vaults and coffers shall be done in such a way as not to damage the product.  
9.2 Shipping  
Transportation will be preferably in containers. Shipping may be also carried out in vehicles whose bed has a 
regula r surface and free from obstacles and/or substances that can damage the product. In this type of 
transport, the load will be  placed on pallets or two suitable supports , placing the vaults and coffers horizontally 
in pallets that reach a maximum height o f 1.7 m above the bed of the vehicle. For this type of transport, the 
load shall also be tied with ropes or straps and the edges of the vaults and the upper coffers will be protected  
with wooden or metal angles to avoid deterioration.  
9.3 Storage  
The vau lts and coffers should be stored under roof and on pallets or wooden supports placed horizontally 
forming pallets that reach heights from 2  400 mm to 3  700 mm. Higher storage heights are allowed, as long as 
there are conditions for the lifting and handling  of the vaults and coffers without causing any damage that 
affects their quality .  
6 © UNBS 2020  – All rights reserved  
 10 Delivery  
10.1 The product shall be delivered with its corresponding certificate of conformity.  
10.2 The certificate of conformity  shall at least bear the following informa tion: 
a) name and address of the manufacturer ; 
b) batch number and date of manufacture ; 
c) quantity of the product ; 
d) nomenclature of the product ; 
e) classification by type and quality class ; 
f) reference number of this Uganda standard ; 
g) identification of the quality inspec tor who evaluated the product;  
h) signature of the person issuing the certificate ; and  
i) date of delivery . FDUS  2225: 2020 
© UNBS 2020  – All rights reserved  7 
 Annex  A 
(normative)  
 
 
A.1 Acceptance inspection  
The acceptance inspection will be carried out by the manufacturer, the project designer, or any other 
authorized body.  
A.2 Sampling plans  
Inspection by attribute ; The AQL for the defects of the slabs and semi -cylinders is 6.5  %. For the inspection by 
attribute, a double sampling plan is established  with a level II for the quality class in accordance with  ISO 
28590 .  
8 © UNBS 2020  – All rights reserved  
 Annex  B 
(normative)  
 
Mechanical properties  
B.1 Minimum compression strength test with 10 % deformation  
B.1.1  Equipment  
B.1.1.1  Test machine  with reading error less than 1 %, constant crushing speed of (10 ± 2) mm/min. It 
shall guarantee the measurement of the deformation with an accuracy of ±0.2 mm.  
B.1.1.2  Scale  with ±0.1 g precision  
B.1.1.3  Vernier callip er with ±0.1 mm precision  
B.1.2  Sample preparation  
B.1.2.1  Three specimens are taken from each sample unit, one from the centre and two from the distance 
of 50 mm of the edge of the sample, with dimensions of (50 X 50) mm. The wet mass is determined on th e 
scale and placed in an oven, maintaining a temperature of (60 ± 2) °C for a time of 3 h. The specimens are 
cooled in a desiccator with calcium chloride anhydrous for 0.5 h and the mass is determined.  
B.1.2.2  The humidity ( W) of the specimens expressed as  a percentage shall be calculated by the 
following equation.  
 
where  
m is mass , in grams, of the wet specimen;  
m1 is mass, in grams,  of the dry specime n. 
B.1.2.3  After determining the length and width of the specimen, it is placed on the support plate of t he test 
machine, so that the compression force acts on the axis of the specimen. Load will be applied until the 
required value for 10 % deformation is obtained.  
B.1.3  Calculation  
B.1.3.1 The minimum compressive strength with deformation at 10 % of deformat ion (Rc), expressed in 
kiloPascals, shall be calculated as shown below.  
 
where  
P is the load at 10  % of deformation ; 
L is the length, in millimetres,  of the specimen;  and FDUS  2225: 2020 
© UNBS 2020  – All rights reserved  9 
 b is the  width,  in millimetres , of the specimen.  
B.1.3.2 As a final result of the t ests, the arithmetic mean (average) of the results obtained shall be taken, 
which shall be in accordance with the specifications in Table 1.  
B.2 Minimum flexural strength test  
B.2.1  Equipment  
B.2.1.1  Any type of machine that is used in the tests of res istance to flexion that allows the displacement 
of the load at a constant speed and that indicates the load with an error not higher than 1 %. Furthermore, the 
apparatus shall allow the placement of the specimen between two parallel supports and separated at a 
chosen distance depending on the thickness of the specimen.  
B.2.1.2  The radius of the supports and the pressure tip will have a minimum value of (3 ± 0.1) mm. For 
thicknesses greater than 3 mm, this value can be 1.5 times the thickness of the specimen . 
B.2.1.3  Vernier caliper  with ± 0.1 mm of precision  
B.2.2 Sample  preparation  
B.2.2.1  Ten (10) specimens are used: five (5) of them cut in the longitudinal axis of the slab and the other 
five (5) in the axis perpendicular to the previous one. The measuremen ts of the specimens are presented in 
Table B.1. 
B.2.2.2  For intermediate values to those specified in Table B.1, the next higher will be taken. If the 
thicknesses are greater than those specified, the samples will be machined by their upper and lower faces  
until achieving one of the mentioned thicknesses. The specimens shall have their edges clean. Before the 
test, they will remain at (23 ± 2) °C and environmental humidity for 4 h.  
Table B.1 — Specimens dimensions  
Thickness  
mm Width  
mm Tolerance  Length , min. 
mm 
0.8 25 
±0.5 50 
1.5 25 50 
2.5 25 60 
3.0 25 80 
5.0 15 100 
6.5 15 130 
9.5 15 190 
12.5 20 250 
19.5 20 380 
25.0 20 500 
 
B.2.3 Procedure  
The dimensions of the specimens are determined in  the calibrated area of each specimen with an a ccuracy of 
±0.5 mm for the width and ±0.2 mm for the thickness. Next, the specimen is placed between the supports, the 
load is applied progressively at a speed chosen according to the thickness of the specimen ( see Table B.2),  
10 © UNBS 2020  – All rights reserved  
 until it breaks. At that mome nt, the value of the load is written down. When the breaking does not occur in the 
central third of the specimen, the test is rejected and a new specimen is retested. It is recommended to plot 
the stress - strain curve.  
Table B.2 — Speed of the test  
Thickn ess 
mm Bridge width  
mm Test speed  
mm/min  
0.8 16 0.5 
1.5 25 0.8 
2.5 40 1.0 
3.0 50 1.5 
5.0 80 2.0 
6.5 100 2.5 
9.5 150 4.0 
12.5 200 5.0 
19.0 300 8.0 
25.0 400 10.0 
NOTE  The speeds should not vary by more than ±50 %  over the referred values .  
 
B.2.4 Calculation  
B.2.4.1  The flexural strength , expressed in Mega Pascals , shall be determined by the following equation.  
 
where  
Ft is the flexural strength, in Mega Pascal s;  
F is the load, in Newtons, at the moment of the break ; 
l is the distance , in millim etres, between the two supports;  
b is the width , in millimetres, of the specimen ; and 
e is thickness , in millimetres, of the specimen . 
B.2.4.2  The value of the flexural strength shall be the arithmetic mean (average) of the values obtained 
with the five te st pieces tested in each direction.  
B.2.4.3  For each direction, the final result of the test shall be indicated, which shall be according to the 
specifications in Table 1.  FDUS  2225: 2020 
© UNBS 2020  – All rights reserved  11 
 Annex  C 
(normative)  
 
Determinatio n of density  
C.1 Equipment  
C.1.1 Scale  with ±0.1 g of precision  
C.1.2 Vernier calliper  with ±0.1 mm of precision   
C.2 Sample  preparation  
C.2.1 A specimen with dimensions (50 x 50) mm is taken from each unit sample. The mass is determined, 
then the width , length and thickness are measured (the thickness will be measured at three points and the 
arithmetic mean taken) and the volume of the specimen is calculated.  
C.2.2 For the determination of the humidity, the procedure used in the minimum stress test with 10 % 
deformation shall be followed.  
C.3 Calculation  
C.3.1 The density , expressed in kilogram s per square meters , shall be calculated by the formula below.  
 
where  
m is the mass , in kilograms , of the specimen;  
V is the volume , in cubic metres,  of the spe cimen;  
w is the humidity , in percentage, of the specimen.  
C.3.2 As a final result of the tests, the arithmetic mean of the results obtained shall be taken, which shall 
comply with the requirement s in Table 1.   
12 © UNBS 2020  – All rights reserved  
 Bibliography  
[1] Europe,  EN 13163:2001 / AC: 2005 , Thermal insulation products for buildings  — Factory made 
products of expanded polystyrene (EPS)  — Specifications  
[2] Germany, DIN 18164: 1991, Rigid cellular plastics insulating building materials. Polystyrene foam 
impact sound insulating m aterials   
[3] Russia, ROCT 12998 -85, Polystyrene film. Specifications  
[4] Venezuela, COVENIN 2344 – 1986, Poliestireno expandible (EPS)  
[5] Venezuela, COVENIN 2345 – 1986 Espumas rígidas de poliestireno expand ido. Determinación de las 
propiedades de flexión   
 US 2225: 2020  
© UNBS 2020  – All rights reserved  13 
 Certification marking  
Products that conform to Uganda standards may be marked with Uganda National Bureau of Standards 
(UNBS) Certification Ma rk shown in the figure below.  
The use of the UNBS Certification Mark is governed by the Standards Act, and the Regulations made 
thereunder. This mark can be used only by those licensed under the certification mark scheme operated by 
the Uganda National Bu reau of Standards and in conjunction with the relevant Uganda Standard. The 
presence of this mark on a product or in relation to a product is an assurance that the goods comply with the 
requirements of that standard under a system of supervision, control a nd testing in accordance with the 
certification mark scheme of the Uganda National Bureau of Standards. UNBS marked products are 
continually checked by UNBS for conformity to that standard.  
Further particulars of the terms and conditions of licensing may be obtained from the Director, Uganda 
National Bureau of Standards.  
 
 US 2225: 2020    
 
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