Highlights of the Code of Practice for Fire Safety in Buildings 2011

7/27/2019 Highlights of the Code of Practice for Fire Safety in Buildings 2011

1/12

Structural Engineering Branch, ArchSD Page 1 of 12 File Code: FS Code.doc

Information PaperCoP for FS in Buildings 2011 MKL/SCF/CHMIssue No./Revision No. : 1/- First Issue Date : June 2012

Information Paper

Highlights

of

The Code of Practice for F ir e Safety in Buildings 2011

STRUCTURAL ENGINEERING BRANCH

ARCHITECTURAL SERVICES DEPARTMENT

June 2012


2/12



1. Introduction

1.1 Regulations 41(1), 41A, 41B, 41C and 41D in the Building (Planning)Regulations and Regulation 90 of the Building (Construction) Regulations.

specify requirements for buildings to be designed in such a way that they exhibit

an acceptable level of performance in the event of fire. Over the years,Buildings Department and Fire Services Department have issued the following

codes on the performance requirements complying the statutory requirements:

a) the Code of Practice for the Provision of Means of Escape 1996(the MOECode);

b) the Code of Practice for Fire Resisting Construction 1996 (the FRCCode);

c) the Code of Practice for Means of Access for Firefighting and Rescue 2004 (the MOA Code);

d) the Code of Practice for Minimum Fire Service Installations andEquipment; and

e) the Code of Practice for Inspection and Testing and Maintenance ofInstallations and Equipment.

1.2 In September 2011, Buildings Department issued the Code of Practice for FireSafety in Buildings 2011(the FS Code), which consolidates and replaces the

requirements of the MOE Code (now Part B of the FS Code), the FRC Code

(now Part C of the FS Code) and the MOA Code (now Part D of the FS Code).

1.3 The Statutory Compliance Checking Unit (the SCCU) of ArchSD hasuploaded a soft copy of the FS Code with highlights of the changes onto

ArchSD Intranet at the following URL:

http://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_f

or_Fire_Safety/Code%20of%20Practice%20for%20Fire%20Safety%20in

%20Buildings%202011%20(amendments%20highlighted%20in%20color

).pdf

The SCCU has further provided detailed comparison the FS Code with the

MOE, FRC and MOA together with summary of key points in powerpoint formand recorded videos of the briefing sessions arranged by Buildings Department

in the following URL:

http://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_f

or_Fire_Safety/Code_of_Practice_for_Fire_Safety.htm

1.4 Section 2 of this paper will highlight:a) the major changes in the FS Code that is most relevant to structural

engineers;

b) the fire resistance rating of hollow-block floors; andc) a summary of the percentage of reinforcement to be provided for reinforced

concrete wall according to the fire resistance rating in the FS Code.
http://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_for_Fire_Safety/Code%20of%20Practice%20for%20Fire%20Safety%20in%20Buildings%202011%20(amendments%20highlighted%20in%20color).pdfhttp://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_for_Fire_Safety/Code%20of%20Practice%20for%20Fire%20Safety%20in%20Buildings%202011%20(amendments%20highlighted%20in%20color).pdfhttp://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_for_Fire_Safety/Code%20of%20Practice%20for%20Fire%20Safety%20in%20Buildings%202011%20(amendments%20highlighted%20in%20color).pdfhttp://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_for_Fire_Safety/Code%20of%20Practice%20for%20Fire%20Safety%20in%20Buildings%202011%20(amendments%20highlighted%20in%20color).pdfhttp://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_for_Fire_Safety/Code%20of%20Practice%20for%20Fire%20Safety%20in%20Buildings%202011%20(amendments%20highlighted%20in%20color).pdfhttp://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_for_Fire_Safety/Code_of_Practice_for_Fire_Safety.htmhttp://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_for_Fire_Safety/Code_of_Practice_for_Fire_Safety.htmhttp://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_for_Fire_Safety/Code_of_Practice_for_Fire_Safety.htmhttp://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_for_Fire_Safety/Code_of_Practice_for_Fire_Safety.htmhttp://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_for_Fire_Safety/Code_of_Practice_for_Fire_Safety.htmhttp://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_for_Fire_Safety/Code%20of%20Practice%20for%20Fire%20Safety%20in%20Buildings%202011%20(amendments%20highlighted%20in%20color).pdfhttp://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_for_Fire_Safety/Code%20of%20Practice%20for%20Fire%20Safety%20in%20Buildings%202011%20(amendments%20highlighted%20in%20color).pdfhttp://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_for_Fire_Safety/Code%20of%20Practice%20for%20Fire%20Safety%20in%20Buildings%202011%20(amendments%20highlighted%20in%20color).pdfhttp://asdiis/cmbiis/cmbiis_a/circulars/SCCU_Corner/Code_of_Practice_for_Fire_Safety/Code%20of%20Practice%20for%20Fire%20Safety%20in%20Buildings%202011%20(amendments%20highlighted%20in%20color).pdf


3/12


4/12



2.3 FRR of Construction and Building Materials

2.3.1 The FS Code Tables E3-E7 (extract as follows) set out minimum dimensions of

different building components for different construction and building materials

for different FRR, which are the same as the FRC Code Tables A-F. There are

no changes on the minimum thickness (including cover for rc construction) forstructural elements (slabs, beams, walls, stairs, columns, etc).

2.3.2 Hollow-block Floors

2.3.2.1 Same as that in FRC Code, the minimum dimensions or cover to

reinforcement for hollow-block floors (or hollow tile floors) are not

mentioned in the FS Code. However, hollow-block floors were commonly

used from the 1950s to 1970s in Hong Kong. They were constructed by

placing precast clay or cement sand blocks (Figure 1) on formwork, and

concrete is then cast to form ribs spanning in one direction (Figure 2). Its

advantages are its lightweight, the excellent sound insulation and thermalinsulation. The clay or cement sand blocks were not usually included in the

design, and hence the topping can be very thin (may be of 50mm). Similarly,

the width of the ribs can be as small as 50mm. Such floor construction is

seldom used nowadays. However, in renovation projects, project officer has

difficulties in assessing the adequacy of its FRR, as there is no provision in the

FS Code on this specific type of floor construction. Applying the minimum

thickness for solid floor construction in the FS Code Table E4, the topping can

hardly achieve a FRR of 60 mins (minimum 100mm), and applying the

minimum width for beam in the FS Code Table E6, the width of the ribs can

again hardly achieve a FRR of 60 mins (minimum 200mm).

Figure 1 Precast Clay or Cement Sand Block

Figure 2 Section of Hollow-block Floor


5/12



2.3.2.2 It seems that ignoring the contribution of the clay blocks in fire resistance is

not a correct assumption, as one of the advantages of hollow-block floors is its

good thermal insulation of the hollow blocks. As a matter of fact, the then

Building (Construction) Regulations 1985 states that the minimum thickness

of the topping (excluding non-combustible finish) for hollow-block floor for

FRR of 30 mins, 60 mins, 120 mins and 240 mins to be respectively 65mm,75mm, 90mm and 125mm. CP 110:Part 1:1972 also specifies the overall

depth (excluding non-combustible finish) for such floor for FRR of 30 mins,

60 mins, 120 mins and 240 mins to be respectively 100mm, 110mm, 160mm

and 190mm. It further specifies the minimum width of the ribs for FRR of 30

mins, 60 mins, 120 mins and 240 mins to be respectively 50mm, 70mm,

90mm and 125mm.

2.3.2.3 The current provision of minimum dimension for hollow-block floors can be

referred to BS 8110-2:1985, which recommends that such type of floor

construction can be treated as solid construction in calculating its fire

resistance by including the contribution of the cement sand or clay blocksusing the effective thickness te given by the following equation:

fe tht

where h is the overall actual thickness of slab;

is the proportion of solid material per unit width of slab;

and tf is the thickness of non-combustible finish.

In some cases, without carrying out detailed measurement of the hollow

blocks to calculate , the topping plus the non-combustible finish may already

be able to achieve the required FRR. Koon (2010) further considered that in

addition to non-combustible plaster, tiles and floor screed may also beincluded as the cover to the reinforcement. Koon (2010) also recommended

the same approach can be used to resolve the requirements of cover for

structural elements in other structural forms (e.g. beam-and-slab construction).

The following example illustrates the calculation of the effective thickness te:

Consider a hollow-block floor with a topping of 75mm, and ribs of width

80mm and depth of 350mm at 500mm c/c as shown in Figure 3. The

thickness of the clay blocks is 20mm. There is also cement sand floor screed

of 25mm.

Figure 3 Typical Hollow-block Floor


6/12



= the proportion of solid material per unit width of slab

=350500

2353601

= 0.517

tf= the thickness of non-combustible finish = 25mm

h = the overall actual thickness of slab = 350mm

Hence, the effective thickness te fth

25517.0350 =277mm

For a FRR of 60 mins, the minimum thickness as specified in the FS Code

Table E4 is 100mm, and hence the effective thickness of the hollow-block

floor slab far exceeds the minimum requirements. Indeed, even ignoring the

contribution of the floor screed, the effective thickness of the hollow-block

slab is 241mm, which already exceeds the specified 100mm. Alternatively,

ignoring the contribution of the clay blocks, the effective thickness of the

hollow-block slab including the floor screed is 100mm, which also meets thespecified 100mm.


7/12




8/12




9/12



2.4 Minimum Percentage of Reinforcement in Reinforced Concrete Walls

2.4.1 Table 1 and Table 2 show respectively the recommended thickness and cover of

reinforced concrete wall with different FRRs and different percentages of

reinforcement as stipulated in the FS Code andBS 8110-2: 1985, and they tallywith each other.


10/12



Table 1: Minimum thickness and cover of rc wall in the FS Code

Reinforced Concrete Wall

Minimum thickness in mm (excluding

plaster) for FRR of

240 mins 120 mins 60 mins

(a) Containing not less than 1% ofvertical reinforcement

180 100 75

Concrete cover to main

reinforcement25 25 15

(b) Containing less than 1% ofvertical reinforcement

240 160 120

Concrete cover to main

reinforcement25 25 25

* where finished with 13mm gypsum plaster on each side, the thickness may be reduced to100mm

(Sources: The FS Code Table E.2)

Table 2: Minimum thickness and cover of r.c. wall in BS 8110

Reinforced Concrete

Wall

Minimum dimensions (in mm) excluding any

combustible finish for a fire resistance of:


Containing over 1.0%

reinforcement

Thickness 180 100 75

Cover 25 25 15

Containing with 0.4% to

1.0% reinforcement

Thickness 240 160 120

Cover 25 25 25

(Sources: BS8110 Table 4.6)

2.4.2 SEB has incorporated the above minimum requirements (Table 3) in the SEB

Standard Drawings no. SD/008 and /009 (URL:

http://asdiis/sebiis/2k/MAIN%20DOC/std_draw/index.htm), and Explanatory

Notes on the Code of Practice for Structural Use of Concrete 2004 (URL:

http://asdiis/sebiis/2k/MAIN%20DOC/info_paper/upload/cop2004_ep.pdf)

further contains the corresponding discussion on the minimum requirements.

Project officer should note that the above minimum provisions are conservative,

as Eurocode 2 now specifies a smaller minimum thickness (Table 4)

irrespective of the cover and percentage of reinforcement for non-load bearingpartition walls.
http://asdiis/sebiis/2k/MAIN%20DOC/std_draw/index.htmhttp://asdiis/sebiis/2k/MAIN%20DOC/std_draw/index.htmhttp://asdiis/sebiis/2k/MAIN%20DOC/info_paper/upload/cop2004_ep.pdfhttp://asdiis/sebiis/2k/MAIN%20DOC/info_paper/upload/cop2004_ep.pdfhttp://asdiis/sebiis/2k/MAIN%20DOC/info_paper/upload/cop2004_ep.pdfhttp://asdiis/sebiis/2k/MAIN%20DOC/std_draw/index.htm


11/12



Table 3(a): Minimum reinforcement for non-load bearing partition wall

Table 3(b): Minimum reinforcement for load bearing wall

Table 4: Minimum thickness of wall in Eurocode 2

Minimum thickness (in mm) for a fire resistance of:


175 120 80(Sources: Eurocode 2 Table 5.3)

2.5 Fire Engineering Approach

The FS Code Part G now replaces APP-87: Guide to Fire EngineeringApproach and dedicates a full section providing guidance and methods on using

the fire engineering approach. Fire engineering approach (or termed as

Alternative Solution in the FS Code) is a performance based method, which is

to ensure that an equivalent level of safety of the building environment is not

eroded without following the Prescriptive Requirements in the FS Code. Forthe structural aspects, SEB is now preparing guidelines on the behaviour of fire

and the structural behaviour of structural steel, reinforced concrete, composite

structure and timber at elevated temperature. Part I of this set of guidelines has

been promulgated and is available in SEB Resource Centre (URL:

http://asdiis/sebiis/2k/resource_centre/).
http://asdiis/sebiis/2k/resource_centre/http://asdiis/sebiis/2k/resource_centre/http://asdiis/sebiis/2k/resource_centre/


12/12



References

Approved document B - Fire safety (2007) (London: NBS/RIBA Publishing)

(available:

http://www.planningportal.gov.uk/buildingregulations/approveddocuments/part

b/; accessed: 2 March 2012)

BSI (1972), CP 110:Part 1:1972- Structural Use of Concrete: Code of Practice

for Design and Construction (London: BSI).

BSI (1985),BS 8110-2: 1985- Structural Use of Concrete: Code of Practice for

Special Circumstances (London: BSI).

Koon, C M (2010), Structural Appraisal of Reinforced Concrete Buildings

with Historic Values,Presented at Seminar on Concrete Damage Assessment,

Concrete Repair and Concrete Mix Technology, Hong Kong, China, 2 February

2010.
http://www.planningportal.gov.uk/buildingregulations/approveddocuments/partb/http://www.planningportal.gov.uk/buildingregulations/approveddocuments/partb/http://www.planningportal.gov.uk/buildingregulations/approveddocuments/partb/http://www.planningportal.gov.uk/buildingregulations/approveddocuments/partb/http://www.planningportal.gov.uk/buildingregulations/approveddocuments/partb/

Documents

Highlights of the Code of Practice for Fire Safety in Buildings 2011