Annex 3A

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995

Fire Engine / Ambulance
1777

Non-Emergency Ambulance

Fire Hazard Reporting

1800 280 0000
General Enquiries

1800 286 5555

Legend: Explanations & Illustrations Rationale Note Figures & Tables Revision history

ANNEX 3A - NOTIONAL PERIODS OF FIRE RESISTANCE

A1.0 General

In this Annex:

a. “Class 1 aggregate” means foamed slag, pumice, blast furnace slag, pelleted fly ash, crushed brick and burnt clay products (including expanded clay) well-burnt clinker and crushed limestone.

b. “Class 2 aggregate” means flint gravel, granite, and all crushed natural stones other than limestones.

c. Any reference to plaster means:

(1) in the case of an external wall 1m or more from the relevant boundary, plaster applied on the internal face only;

(2) in the case of any other wall, plaster applied on both faces;

(3) if to plaster of a given thickness on the external face of a wall, except in the case of a reference to vermiculite-gypsum plaster, rendering on the external face of the same thickness; and

(4) if to vermiculite-gypsum plaster, vermiculite-gypsum plaster of a mix within the range of 1½ to 2:1 by volume.

d. In the case of a cavity wall, the load is assumed to be on inner leaf only except for fire resistance period of 4-hrs.

e. Any material or type of construction and its method of preparation or application as referred to in the table, shall conform with the relevant provisions of the Building Control Act (Chapter 29) and the relevant Singapore Standard or Singapore Standard Code of Practice. In the absence of the aforementioned Standard or Code of Practice, the relevant British equivalent or other accepted standard or codes of practice shall be applicable.

A2.0 : WALLS
Construction and Materials	Minimum thickness excluding plaster (in mm) for period of fire resistance of
	Load-bearing						Non-load-bearing
	4 hrs	3 hrs	2 hrs	1½ hrs	1 hr	½ hr	4 hrs	3 hrs	2 hrs	1½ hrs	1 hr	½ hr
A2.1 -- Mansonry Construction
1. Reinforced concrete, minimum concrete cover to main reinforcement of 25mm:
(a) Unplastered (to comply with SS EN 1992–1–2)	-	-	-	-	-	-	-	-	-	-	-	-
(b) 12.5mm cement-sand plaster	180	-	100	100	75	75	-	-	-	-	-	-
(c) 12.5mm gypsum-sand plaster	180	-	100	100	75	75	-	-	-	-	-	-
(d) 12.5mm vermiculite-gypsum plaster	125	-	75	75	63	63	-	-	-	-	-	-
2. No-fines concrete of Class 2 aggregate:
(a) 13mm cement-sand plaster	-	-	-	-	-	-	150	150	150	150	150	150
(b) 13mm gypsum-sand plaster	-	-	-	-	-	-	150	150	150	150	150	150
(c) 13mm vermiculite-gypsum plaster	-	-	-	-	-	-	150	150	150	150	150	150
3. Bricks of clay, concrete or sand-lime:
(a) Unplastered	200	200	100	100	100	100	170	170	100	100	75	75
(b) 13mm cement-sand plaster	200	200	100	100	100	100	170	170	100	100	75	75
(c) 13mm gypsum-sand plaster	200	200	100	100	100	100	170	170	100	100	75	75
(d) 13mm vermiculite-gypsum or perlite-gypsum* plaster	100	-	100	100	100	100	100	-	100	100	75	75
4. Concrete blocks of Class 1 aggregate:
(a) Unplastered	150	-	100	100	100	100	150	-	75	75	75	50
(b) 12.5mm cement-sand plaster	150	-	100	100	100	100	150	-	75	75	75	50
(c) 12.5mm gypsum-sand plaster	150	-	100	100	100	100	150	-	75	75	75	50
(d) 12.5mm vermiculite-gypsum plaster	100	-	100	100	100	100	75	-	75	62	50	50
5. Concrete blocks of Class 2 aggregate:
(a) Unplastered	-	-	100	100	100	100	150	-	100	100	75	50
(b) 12.5mm cement-sand plaster	-	-	100	100	100	100	150	-	100	100	75	50
(c) 12.5mm gypsum-sand plaster	-	-	100	100	100	100	150	-	100	100	75	50
(d) 12.5mm vermiculite-gypsum plaster	100	-	100	100	100	100	100	-	75	75	75	50
6. Autoclaved aerated concrete blocks, density 475 - 1200 kg/m³	180	140	100	100	100	100	100	-	62	62	50	50
7. Hollow concrete blocks, one cell in wall thickness, of Class 1 aggregate:
(a) Unplastered	-	-	100	100	100	100	150	-	100	100	100	75
(b) 12.5mm cement-sand plaster	-	-	100	100	100	100	150	-	100	75	75	75
(c) 12.5mm gypsum-sand plaster	-	-	100	100	100	100	150	-	100	75	75	75
(d) 12.5mm vermiculite-gypsum plaster	-	-	100	100	100	100	150	-	75	75	62	62
8. Hollow concrete blocks, one cell in wall thickness, of Class 2 aggregate:
(a) Unplastered	-	-	-	-	-	-	150	-	150	125	125	125
(b) 12.5mm cement-sand plaster	-	-	-	-	-	-	150	-	150	125	125	100
(c) 12.5mm gypsum-sand plaster	-	-	-	-	-	-	150	-	150	125	125	100
(d) 12.5mm gypsum-sand plaster	-	-	-	-	-	-	125	-	100	100	100	75
9. Cellular clay blocks not less than 50% solid
(a) 12.5mm cement-sand plaster	-	-	-	-	-	-	-	-	-	-	100	75
(b) 12.5mm gypsum-sand plaster	-	-	-	-	-	-	-	-	-	-	100	75
(c) 12.5mm vermiculite-gypsum plaster	-	-	-	-	-	-	200	-	100	100	100	62
10. Cavity wall with outer leaf of bricks or blocks of clay, composition, concrete or sand-lime, not less than 100mm thick and;
(a) inner leaf of bricks or blocks of clay, composition, concrete or sand lime	100	100	100	100	100	100	75	-	75	75	75	75
(b) inner leaf of solid or hollow concrete bricks or blocks of Class 1 aggregate	100	100	100	100	100	100	75	-	75	75	75	75
11. Cavity wall with outer leaf of cellular clay blocks as 9 above and inner leaf of autoclaved aerated concrete blocks, density 480-1200 kg/m³	150	140	100	100	100	100	75	75	75	75	75	75
Note: * - Perlite-gypsum plaster to clay bricks only

A2.0 : WALLS
Construction and Materials	Period of Fire Resistance hrs
A2.2 - Framed and Composite Construction (non-load-bearing)
1. Steel frame with external cladding of 16mm rendering on metal lathing and internal lining of autoclaved aerated concrete blocks, density 480-1120 kg/m³ of thickness of –
(a) 50mm	2
(b) 62mm	3
(c) 75mm	4
2. Steel frame with external cladding of 100mm concrete blocks and internal lining of 16mm gypsum plaster on metal lathing	4
3. Steel frame with external cladding of 16mm rendering on metal lathing and internal lining of 16mm gypsum plaster on metal lathing	1
4. Steel or timber frame with facings on each side of -
(a) metal lathing with cement-sand or gypsum plaster of thickness of-
(1) 19mm	1
(2) 12.5mm	½
(b) metal lathing with vermiculite-gypsum or perlite-gypsum plaster of thickness of-
(1) 25mm	2
(2) 19mm	1½
(3) 12.5mm	1
(c) 9.5mm plasterboard with gypsum plaster of thickness of 5mm	½
(d) 9.5mm plasterboard with vermiculite-gypsum of thickness of-
(1) 25mm	2
(2) 16mm	1½
(3) 10mm	1
(4) 5mm	½
(e) 12.5mm plasterboard
(1) unplastered	½
(2) with gypsum plaster of thickness of 12.5mm	1
(f) 12.5mm plasterboard with vermiculite-gypsum plaster of thickness of-
(1) 25mm	2
(2) 16mm	1 ½
(3) 10mm	1
(g) 19mm plasterboard (or two layers of 9.5mm fixed to break joint) without finish	1
(h) 19mm plasterboard for two layers of 9.5mm with vermiculite-gypsum plaster of thickness of-
(1) 16mm	2
(2) 10mm	1 ½
(i) 12.5mm fibre insulating board with gypsum plaster of thickness of 12.5mm	½
(j) 25mm wood wool slabs with gypsum plaster of thickness of 12.5mm	1
5. Compressed straw slabs in timber frames finished on both faces with gypsum plaster of thickness of 5mm	1
6. Plasterboard 9.5mm cellular core partition-
(a) unplastered	½
(b) 12.5mm gypsum plaster	½
(c) 22mm vermiculite-gypsum plaster	2
7. Plasterboard 12.5mm cellular core partition-
(a) unplastered	½
(b) 12.5mm gypsum plaster	1
(c) 16mm vermiculite-gypsum plaster	2
8. Plasterboard 19mm finished on both faces with 16mm gypsum plaster	1
9. Plasterboard 12.5mm bonded with neat gypsum plaster to each side of 19mm plasterboard	1
10. Three layers of 19mm plasterboard bonded with heat gypsum plaster	2
11. Wood wool slab with 12.5mm rendering or plaster of thickness of-
(a) 75mm	2
(b) 50mm	1
12. Compressed straw slabs, with 75mm by 12.5mm wood cover strips to joints, of thickness of 50mm	½
Note : * - The presence of a combustible vapour barrier within the thickness of these constructions shall not be regarded as affecting these periods of fire resistance

A2.0 : WALLS
Construction and Materials	Period of Fire Resistance hrs
A2.3 - External walls (non-loadbearing) more than 1m from the relevant boundary
1. Steel frame with external cladding of non-combustible sheets and internal lining of-
(a) 12.5mm cement-sand or gypsum plaster on metal lathing	4
(b) two layers of 9.5mm plasterboard	½
(c) 9.5mm plasterboard finished with gypsum plaster of thickness of 12.5mm	½
(d) 12.5mm plasterboard finished with 5mm gypsum plaster	½
(e) 50mm compressed straw slabs	½
(f) 50mm compressed straw slabs finished with 5mm gypsum plaster	2
2 *Timber frame with external cladding of 10mm cement-sand or cement-lime rendering and internal lining of-
(a) 16mm gypsum plaster on metal lathing	1
(b) 9.5mm plasterboard finished with12.5 mm gypsum plaster	1
(c) 12.5mm plasterboard finished with 5mm gypsum plaster	1
(d) 50mm compressed straw slabs	1
(e) aerated concrete blocks	1
(1) 50mm	3
(2) 62mm	4
(3) 75mm	4
(4) 100mm	4
3 Timber frame with external cladding of 100mm clay, concrete or sand-lime bricks of blocks, finished internally with 16mm gypsum plaster on metal lathing	4
4. *Timber frame with external cladding of weather boarding or 9.5 mm plywood and internal lining of-
(a) 16mm gypsum plaster on metal lathing	½
(b) 9.5mm plasterboard finished with 12.5mm gypsum plaster	½
(c) 12.5mm plasterboard finished with 5mm gypsum plaster	½
(d) 50mm compressed straw slabs	½
(e) aerated concrete blocks-
(1) 50mm	3
(2) 62mm	4
(3) 75mm	4
(4) 100mm	4
Note: * - The presence of a combustible vapour barrier within the thickness of these constructions shall not be regarded as affecting these periods of fire resistance

A3.0: REINFORCED CONCRETE BEAMS
Description	Minimum Dimension (mm) of Concrete to give a Fire Resistance of:-
Description	4 hrs	3 hrs	2 hrs	1 ½ hrs	1 hr	½ hr
1 Siliceous aggregate concrete:
(a) average concrete cover to main reinforcement	65*	55*	45*	35	25	15
(b) beam width	280	240	180	140	110	80
2. As (1) with cement or gypsum plaster 15mm thick on light mesh reinforcement
(a) average concrete cover to main reinforcement	50*	40	30	20	15	15
(b) beam width	250	210	170	110	85	70
3. As (1) with vermiculite/ gypsum plaster⁺ 15mm thick:
(a) average concrete cover to main reinforcement	25	15	15	15	15	15
(b) beam width	175	145	125	85	60	60
4. Light weight aggregate concrete:
(a) average concrete cover to main reinforcement	50	45	35	30	20	15
(b) beam width	250	200	160	130	100	80
Note: * - Supplementary reinforcement, to hold the concrete cover in position, may be necessary ⁺ - Vermiculite/ gypsum plaster should have a mix ratio in the range of 1 ½ - 2: 1 by volume

A4.0: PRESTRESSED CONCRETE BEAMS
Description	Minimum Dimension (mm) of Concrete to give a Fire Resistance of:-
Description	4 hrs	3 hrs	2 hrs	1 ½ hrs	1 hr	½ hr
1 Siliceous aggregate concrete:
(a) average concrete cover to tendons	100*	85*	65*	50*	40	25
(b) beam width	280	240	180	140	110	80
2. As (1) with vermiculite concrete slabs 15mm thick , used as permanent shuttering:
(a) average concrete cover to tendons	75*	60	45	35	25	15
(b) beam width	210	170	125	100	70	70
3. As (2) but with 25mm thick slabs:
(a) average concrete cover to tendons	65	50	35	25	15	15
(b) beam width	180	140	100	70	60	60
4. As (1) with 15mm thick gypsum plaster with light mesh reinforcement:
(a) average concrete cover to tendons	90*	75	50	40	30	15
(b) beam width	250	210	170	110	85	70
5. As (1) with vermiculite/gypsum plaster⁺ 15m thick:
(a) average concrete cover to tendons	75*	60	45	30	25	15
(b) beam width	170	145	125	85	60	60
6. As (5) but with 25mm thick coating:
(a) average concrete cover to tendons	50	45	30	25	15	15
(b) beam width	140	125	85	70	60	60
7. Lightweight aggregate concrete:
(a) average concrete cover to tendons	80	65	50	40	30	20
(b) beam width	250	200	160	130	100	80
Note: * - Supplementary reinforcement, to hold the concrete cover in position, may be necessary ⁺ - Vermiculite/gypsum plaster should have a mix ratio in the range of 1 ½ - 2: 1 by volume

A5.0: REINFORCED CONCRETE COLUMNS
Description	Minimum Dimension (mm) of Concrete to give a Fire Resistance of:-
Description	4 hrs	3 hrs	2 hrs	1½ hrs	1 hr	½ hr
A5.1 - All Face Exposed
1. Siliceous aggregate concrete:
(a) without additional protection	450	400	300	250	200	150
(b) with cement or gypsum plaster 15mm thick on light mesh reinforcement	300	275	225	150	150	150
(c) with vermiculite/ gypsum plaster*	275	225	200	150	120	120
2. Limestone aggregate concrete or siliceous aggregate:
(a) concrete with supplementary reinforcement in concrete cover	300	275	225	200	190	150
3. Lightweight aggregate concrete	300	275	225	200	150	150
A5.2 - One Face Exposed
1. Siliceous aggregate concrete
(a) without additional protection	180	150	100	100	75	75
(b) with vermiculite/ gypsum plaster* 15mm thick on exposed faces	125	100	75	75	65	65
Note: ⁺ - Vermiculite/gypsum plaster should have a mix ratio in the range of 1 ½ - 2: 1 by volume

A6.0: STRUCTURAL STEEL
A6.1 - Encased Steel Stanchions (Mass per metre not less than 45kg)
Description	Minimum Thickness (mm) of Protection for a Fire Resistance of:
Description	4 hrs	3 hrs	2 hrs	1 ½hrs	1 hr	½hr
A. Solid Protection* (Unplastered)
1. Concrete not leaner than 1:2:4 mix with natural aggregates-
(a) concrete not assumed to be load- bearing reinforced⁺	50	-	25	25	25	25
(b) concrete assumed to be load-bearing, reinforced in accordance with SS EN 1992 and SS EN 1994	75	-	50	50	50	50
2. Solid bricks of clay, composition or sand-lime	100	75	50	50	50	50
3. Solid blocks of foamed slag or pumice concrete reinforced⁺ in every horizontal joint	75	60	50	50	50	50
4. Sprayed vermiculite-cement	-	-	38	32	19	12.5
B. Hollow Protection⁺⁺
1. Solid bricks of clay, composition or sandlime reinforced in every horizontal joint, unplastered	115	-	50	50	50	50
2. Solid blocks of foamed slag or pumice concrete reinforced⁺ in every horizontal joint, unplastered	75	-	50	50	50	50
3. Metal lathing with gypsum or cement- lime plaster of thickness of -	-	-	38^§	25	19	12.5
4. Metal lathing:-
(a) with vermiculite-gypsum or perlite-gypsum plaster of thickness of	50^§	-	19	16	12.5	12.5
(b) spaced 25mm from flanges with vermiculite-gypsum or perlite-gypsum plaster of thickness of	44	-	19	12.5	12.5	12.5
5. Gypsum plasterboard with 1.6mm wire binding at 100mm pitch -
(a) 9.5mm Plasterboard with gypsum plaster of thickness of	-	-	-	-	12.5	12.5
(b) 19mm Plasterboard with gypsum plaster of thickness of	-	-	12.5	10	7	7
6. Gypsum plasterboard with 1.6mm wire binding at 100mm pitch-
(a) 9.5mm plasterboard with vermiculite-gypsum plaster of thickness of	-	-	16	15	10	10
(b) 19mm plasterboard with vermiculite-gypsum plaster of thickness of	38^§	-	20	13	10	10
7. Vermiculite-cement slabs of 4:1 mix reinforced with wire mesh and finished with plaster skim. Slabs of thickness of	63	-	25	25	25	25
Note: * - Solid protection means a casing which is bedded close to the steel without intervening cavities and with all joints in that casing made full and solid ⁺ - Reinforcement shall consist of steel binding wire not less than 2.3mm in thickness, or a steel mesh weighing not less than 0.48 kg/m². In concrete protection, the spacing of that reinforcement shall not exceed 150mm in any direction ⁺⁺ - Hollow protection means that there is a void between the protective material and the steel. All hollow protection to columns shall be effectively sealed at each floor level ^§ - Light mesh reinforcement required 12.5mm to 19mm below surface unless special corner beads are used

A6.2 - Encased Steel Beams (Mass per metre not less than 30kg)
Description	Minimum Thickness (mm) of Protection for a Fire Resistance of :
Description	4 hrs	3 hrs	2 hrs	1½ hrs	1 hr	½ hr
A. Solid Protection+ (Unplastered)
1. Concrete not leaner than 1:2:4 mix with natural aggregates-
(a) concrete not assumed to be load- bearing, reinforced⁺⁺	75	50	25	25	25	25
(b) concrete assumed to be load-bearing, reinforced in accordance with SS EN 1992 and SS EN 1994	75	75	50	50	50	50
2. Sprayed vermiculite - cement	-	-	38	32	19	12.5
B. Hollow Protection⁺⁺
1. Metal lathing -
(a) with cement-lime plaster of thickness of	-	-	38	25	19	12.5
(b) with gypsum plaster of thickness of	-	-	22	19	16	12.5
(c) with vermiculite-gypsum or perlite-gypsum plaster of thickness of	32	-	12.5	12.5	12.5	12.5
2. Gypsum plasterboard with 1.6mm wire binding at 100mm pitch-
(a) 9.5mm plasterboard with gypsum plaster of thickness of	-	-	-	-	12.5	12.5
(b) 19 mm plasterboard with gypsum plaster of thickness of	-	-	12.5	10	7	7
3. Plasterboard with 1.6mm wire at 100m pitch -
(a) 9.5mm plaster nailed to wooden cradles finished with gypsum plaster of thickness of	-	-	-	-	-	12.5
(b) 9.5mm plasterboard with vermiculite -gypsum plaster of thickness of	-	-	16	15	10	10
(c) 19mm plasterboard with vermiculite-gypsum plaster of thickness of	32	-	10	10	7	7
(d) 19mm plasterboard with gypsum plaster of thickness of	-	-	20	13	10	10
4. Vermiculite-cement slabs of 4:1 mix reinforced with wire mesh and finished with plaster skim. Slabs of thickness of	63	-	25	25	25	25
5. Gypsum-sand plaster 12.5mm thick applied to heavy duty (Type B as designated in EN 13168) Wood wool slabs of thickness of	-	-	50	38	38	38
Note: * - Hollow protection means that there is a void between the protective materials and the steel. All hollow protection to columns shall be effectively sealed at each floor level ⁺ - Solid protection means a casing which is bedded close to the steel without intervening cavities and with all joints in that casing made full and solid ⁺⁺ - Reinforcement shall consist of steel binding wire not less than 2.3mm in thickness, or a steel mesh weighing not less than 0.48 kg/m². In concrete protection, the spacing of that reinforcement shall not exceed 150mm in any direction ^§ - Light mesh reinforcement required 12.5mm to 19mm below surface unless special corner beads are used

A7.0: STRUCTURAL ALUMINIUM
Description	Minimum Thickness (mm) of Protection for a Fire Resistance of :
Description	4 hrs	3 hrs	2 hrs	1½ hrs	1 hr	½ hr
A7.1 - Solid Protection*
1. Sprayed vermiculite-cement	-	-	-	-	44	19
A7.2 - Hollow Protection⁺
1. Metal lathing with vermiculite-gypsum or perlite-gypsum plaster of thickness of	-	-	32	22	16	12.5
2. Metal lathing finished with neat gypsum plaster of thickness of	-	-	-	-	19	12.5
3. Gypsum plasterboard 19mm thick with 1.6 mm wire binding at 100mm pitch finished with gypsum-vermiculite plaster of thickness of	-	-	22	16	10	10
Note: * - Solid protection means a casing which is bedded close to the alloy without intervening cavities and with all joints in that casing made full and solid ⁺ - Hollow protection means that there is a void between the protected material and the alloy. All hollow protection to columns shall be effectively sealed at each floor level

A8.0: TIMBER FLOORS
Construction and materials	Minimum Thickness (mm) of Protection for a Fire Resistance of:
Construction and materials	1 hr	½ hr	modified⁺⁺½ hr
1. Plain edge boarding on timber joists not less than 38mm wide with ceiling of -
(a) timber lath and plaster - thickness of plaster	-	16	16
(b) timber lath and plaster with plaster of minimum thickness of 16mm covered on underside with plasterboard of thickness	-	12.5	-
(c) metal lathing and plaster - thickness of plaster
(1) gypsum	-	16	-
(2) vermiculite	-	12.5	-
(d) one layer of plasterboard of thickness	-	-	12.5
(e) one layer of plasterboard of minimum thickness of 9.5mm finished with gypsum plaster of thickness	-	-	12.5
(f) one layer of plasterboards of minimum thickness of 12.5mm finished with gypsum plaster of thickness	-	12.5	-
(g) two layers of plasterboard of total thickness	-	25	19
(h) one layer of fibre insulating board of minimum thickness of 9.5mm finished with gypsum plaster of thickness	-	5	-
(i) one layer of fibre insulating board of minimum thickness of 12.5mm finished with gypsum plaster of thickness	-	-	12.5
(j) wood wool slab 25mm thick finished with gypsum plaster of thickness	-	5	-
2. Tongued and grooved boarding of not less than 16mm (finished) thickness* on timber joists not less than 38 mm wide ceiling of -
(a) timber lath and plaster - thickness of plaster	-	-	16
(b) timber lath and plaster with plaster of minimum thickness of 16mm covered on underside with plasterboard of thickness	-	9.5	-
(c) metal lathing and plaster - thickness of plaster
(1) gypsum	22	16	-
(2) vermiculite	12.5	12.5	-
(d) one layer of plasterboard of thickness	-	-	9.5
(e) one layer of plasterboard of minimum thickness of 9.5mm finished with-
(1) gypsum plaster of thickness	-	12.5	-
(2) vermiculite-gypsum plaster of thickness	12.5	-	-
(f) one layer of plasterboards of minimum thickness of 12.5mm finished with gypsum plaster of thickness	-	5	-
(g) two layers of plasterboard of total thickness	-	22	-
(h) one layer of fibre insulating board of minimum thickness of 9.5mm finished with gypsum plaster of thickness	-	-	5
(i) wood wool slab 25mm thick finished with -
(1) gypsum plaster of thickness	-	5	-
(2) vermiculite - gypsum plaster of thickness	10	-	-
3. Tongued and grooved boardings of not less than 21mm (finished) thickness* on timber joists not less than
(a) timber lath and plaster - thickness of plaster	-	16	-
(b) metal lathing and plaster - thickness of plaster	-	16	-
(c) one layer of plasterboard of thickness	-	-	9.5
(d) one layer of plasterboard of minimum thickness of 9.5mm finished with -
(1) gypsum plaster of thickness	-	12.5	-
(2) vermiculite-gypsum plaster of thickness	12.5	-	-
(e) one layer of plasterboard of minimum thickness of 12.5mm finished with gypsum plaster of thickness	-	5	-
(f) two layers of plasterboard of total thickness	-	19	-
(g) one layer of fibre insulating board of thickness	-	-	12.5
(h) one layer of fibre insulating board of minimum thickness of 12.5mm finished with gypsum plaster of thickness	-	12.5	-
(i) wood wool slab 25mm thick finished with -
(1) gypsum plaster of thickness	-	5	-
(2) vermiculite-gypsum plaster of thickness	10	-	-
Note: * - Or an equivalent thickness of wood chipboard ⁺⁺ - The term “modified ½ hour” refers to the requirements specified in item 3(a) of Table 3.4A

A9.0: REINFORCED CONCRETE FLOORS (SILICEOUS OR CALCAREOUS AGGREGATE)
Floor Construction		Minimum Dimension (mm) to give Fire Resistance of :
Floor Construction		4 hrs	3 hrs	2 hrs	1 ½ hrs	1 hr	½ hr
Solid slab	Average cover to reinforcement	25	25	20	20	15	15
Solid slab	Depth, overall⁺	150	150	125	125	100	100
Cored slabs in which the cores are circular or are higher than wide. Not less than 50% of the gross across section of the floor should be solid material	Average cover to reinforcement	25	25	20	20	15	15
	Thickness under cores	50	40	40	30	25	20
	Depth, overall⁺	190	175	160	140	110	100
Hollow box section with one or more longitudinal cavities which are wider than high	Average cover to reinforcement	25	25	20	20	15	15
	Thickness of bottom flange	50	40	40	30	25	20
	Depth, overall⁺	230	205	180	155	130	105
Ribbed floor with hollow infill blocks of clay, or inverted T-section beams with hollow infill blocks of concrete or clay. A floor in which less than 50% of the gross cross section is solid material must be provided with a 15mm plaster coating on soffit	Average cover to reinforcement	25	25	20	20	15	15
	Width or rib, or beam, at soffit	125	100	90	80	70	50
	Depth, overall⁺	190	175	160	140	110	100
Upright T-section	Average bottom cover to reinforcement	65*	55*	45*	35	25	15
	Side cover to reinforcement	65	55	45	35	25	15
	Least width or down-standing leg	150	140	115	90	75	60
	Thickness of flange⁺	150	150	125	125	100	90
Inverted channel sections with radius at intersection of soffits with top of leg not exceeding depth of section	Average bottom cover to reinforcement	65*	55*	45*	35	25	15
	Side cover to reinforcement	40	30	25	20	15	10
	Least width or down-standing leg	75	70	60	45	40	30
	Thickness at crown⁺	150	150	125	125	100	90
Inverted channel sections or U-sections with radius at intersection of soffits with top of leg exceeding depth of section	Average bottom cover to reinforcement	65*	55*	45*	35	25	15
	Side cover to reinforcement	40	30	25	20	15	10
	Least width or down-standing leg	70	60	50	40	35	25
	Thickness at crown⁺	150	150	100	100	75	65
Note: * - Supplementary reinforcement, to hold the concrete cover in position, may be necessary ⁺ - Non-combustible screeds and finishes may be included in these dimensions

A10.0: PRESTRESSED CONCRETE FLOORS (SILICEOUS OR CALCAREOUS AGGREGATE)
Floor Construction		Minimum Dimension (mm) to give Fire Resistance of :
Floor Construction		4 hrs	3 hrs	2 hrs	1 ½ hrs	1 hr	½ hr
Solid slab	Average cover to reinforcement	65*	50*	40	30	25	15
Solid slab	Depth, overall⁺	150	150	125	125	100	90
Cored slabs in which the cores are circular or are higher than wide. Not less than 50% of the gross across section of the floor should be solid material	Average cover to reinforcement	65*	50*	40	30	25	15
	Thickness under cores	50	40	40	30	25	20
	Depth, overall⁺	190	175	160	140	110	100
Hollow box section with one or more longitudinal cavities which are wider than high	Average cover to reinforcement	65*	50*	40	30	25	15
	Thickness of bottom flange	65	50	40	30	25	25
	Depth, overall⁺	230	205	180	155	130	105
Ribbed floor with hollow infill blocks of clay, or inverted T-section beams with hollow infill blocks of concrete or clay. A floor in which less than 50% of the gross cross section is solid material must be provided with a 15mm plaster coating on soffit	Average cover to reinforcement	65*	50*	40	30	25	15
	Width or rib, or beam, at soffit	125	100	90	80	70	50
	Depth, overall⁺	190	175	160	140	110	100
Upright T-section	Average bottom cover to reinforcement	100*	85*	65*	50*	40	25
	Side cover to reinforcement	100	85	65	50	40	25
	Least width or down-standing leg	250	200	150	110	90	60
	Thickness of flange⁺	150	150	125	125	100	90
Inverted channel sections with radius at intersection of soffits with top of leg not exceeding depth of section	Average bottom cover to reinforcement	100*	85*	65*	50*	40	25
	Side cover to reinforcement	50	45	35	25	20	10
	Least width or down-standing leg	125	100	75	55	45	30
	Thickness at crown⁺	150	150	125	125	100	90
Inverted channel sections or U-sections with radius at intersection of soffits with top of leg exceeding depth of section	Average bottom cover to reinforcement	100*	85*	65*	50*	40	25
	Side cover to reinforcement	50	45	35	25	20	15
	Least width or down-standing leg	110	90	70	50	45	30
	Thickness at crown⁺	150	150	125	125	100	90
Note: * - Supplementary reinforcement, to hold the concrete cover in position, may be necessary ⁺ - Non-combustible screeds and finishes may be included in these dimensions

A11.0: GLAZING
Construction and materials	Minimum Thickness (mm) of Glazing for a Period of:-
Construction and materials	1 hr	½ hr
1. Glass, in direct combination with metal, the melting point of which is not lower than 982.2°C, in square not exceeding 0.015m² in area
Thickness of glass	-	6.35
2. Glass reinforced with wire not less than 0.46mm in diameter laid to a square mesh measuring 12.70mm from centre to centre of wire, and electrically welded at the intersections, or laid to a hexagonal mesh measuring 25.40mm across the flat side
Thickness of glass	-	6.35
In windows, doors , borrowed lights, lanterns and skylights, glass complying with paragraphs 1 or 2 of this Table shall be fixed with wood or metal beads or with a glazing compound in conjunction with sprigs or clips in panels not exceeding 0.372m ² in area in timber frames (fixed shut) having a minimum width and thickness of 44.45mm clear of rebates
3. Glass reinforced with wire as in paragraph 2 of this Table, in windows, doors, borrowed lights, lanterns and skylights, fixed with metal beads in panels not exceeding 1.115m² in metal frames (fixed shut) all metal having a melting point not lower than 982.2^oC, the thickness of glass	6.35	6.35
4. Glass bricks or blocks in walls
Laid in cement / lime / sand mortar with light wire reinforcing mesh in every third horizontal joint in a panel not exceeding 2.438m in width or height set along the sides and head into recesses in the surrounding non-combustible construction. The depth of such recessed shall be not less than 25.40mm, the glass blocks extending into the recesses to a depth of 12.70mm and bedded upon layer of glass fibre. A non-hardening mastic shall be used to fill the spaces between the sides of the recesses and the faces of the panels	-	98.43
Note: In this Table the absence of a figure in a period column indicated that glazing described is not acceptable for the period applicable to that column

Updated 2 Sep 2024

Related tables

Annex 3B