What fire resistance period does a 2-storey house need?

Thirty minutes. Table B2 in Appendix B of Approved Document B gives rows 1(b) and 1(c) Dwellinghouse a period of 30 minutes in the "Up to 5" column, which is read on the height of the top floor above ground and not on the storey count. The notes to Table B2 add that for single storey buildings the periods under the heading "Up to 5" apply. Two qualifications sit on that cell. The dagger note reads: for compartment walls that separate buildings, the period is increased to a minimum of 60 minutes. And Table B1 item 3(b) treats the floor in the upper storey of a two storey dwellinghouse separately, at R 30 and EI 15 rather than REI 30, provided it is not over a garage or a basement.

When is 60-minute fire resistance required?

For a dwellinghouse, Table B2 prints 60 minutes in the "Up to 11" and "Up to 18" columns, and both cells carry note 5: a minimum of 30 minutes in the case of three storey dwellinghouses, increased to 60 minutes minimum for compartment walls separating buildings. So a three storey house is not automatically a 60 minute building. For a block of flats, row 1(a) gives 60 minutes at "Up to 11" on both the sprinklered and the unsprinklered line, and 60 minutes at "Up to 18" on the sprinklered line only, because the unsprinklered line reads "Not permitted" above 11m and note 2 makes sprinklers mandatory there. Rows 2(a) residential institutional and 2(b) other residential are 60 minutes across both those bands, as is an unsprinklered office. An unsprinklered shop, assembly, industrial or storage building is already above 30 minutes at "Up to 5".

What period applies to a house taller than 18 m?

Approved Document B does not give one. Table B2 rows 1(b) and 1(c) print "Not applicable" in the "Up to 30" column, the "More than 30" column and the basement column for a lowest basement more than 10m deep. Note 4 says why, verbatim: "Very large (with a top storey more than 18m above ground level or with a 10m deep basement) or unusual dwellinghouses are outside the scope of the guidance provided with regard to dwellinghouses." There is no Approved Document period to quote for that building, so quoting 90 or 120 minutes for it would be inventing a figure the guidance declines to give. Design it with a fire engineer, normally to BS 9991, and agree the strategy with your building control body. A block of flats of the same height is a different purpose group, 1(a), and does have figures: 90 minutes up to 30m and 120 minutes above 30m, both on the sprinklered line.

What fire rating do internal doors need?

Fire doorset provisions come from Table C1 in Appendix C, not from the period of the surrounding construction, so they are often a different number. A doorset forming part of the enclosures to a protected stairway in a single family dwellinghouse is E 20 (FD 20) under Table C1 item 11(b), and Appendix C5 exempts fire doorsets within flats and dwellinghouses from the self-closing requirement, so it needs no self-closer and Table C1 attaches no smoke suffix to it. A door in a compartment wall separating a flat from a space in common use, which is the flat entrance door, is E 30 Sa (FD 30 S) under item 2(a). The door between a dwellinghouse and a garage is E 30 Sa (FD 30 S) under item 11(a) and C5 names it expressly as one that must be self-closing. A protected corridor door is E 30 Sa (FD 30 S) only where the corridor is a lobby approach to a stairway (item 5(a)); any other protected corridor is E 20 Sa (FD 20 S) under item 5(b). FD 20 doorsets are no longer certified as products, so an FD 30 door is the practical way to satisfy an E 20 requirement.

How is fire resistance tested and certified?

Fire resistance is established by testing to BS EN 1363 and classified to BS EN 13501-2. Table B1 note 1 sets out what the letters mean: R is the resistance to fire in terms of loadbearing capacity, E is the resistance in terms of integrity, and I is the resistance in terms of insulation. An REI 60 element holds all three for 60 minutes. Table B1 also gives alternative minimum provisions tested to the relevant part of BS 476, and its note 1 warns that the national classifications do not automatically equate with the European ones, so a product cannot be assumed to hold a European class unless it has been tested to it.

Part B Fire Resistance Ratings Reference

Minimum Periods of Fire Resistance (AD B Appendix B, Table B2)

Table B2 is the only table in Approved Document B that sets minimum periods of fire resistance for elements of structure, and it is identical in Volume 1 (Dwellings) and Volume 2 (Buildings other than dwellings). You read it by purpose group down the side, then by the height of the top floor above ground across the top, with two further columns read on the depth of the lowest basement. The version below carries the banner “Effective until 1 September 2029”, so it is the in-force version.

Two headings that are easy to misread. The height columns are the height of the top floor above ground in a building or separated part of a building, not the number of storeys, and the notes state that for single storey buildings the periods under the heading “Up to 5” apply. Purpose group 1(a) is the block of flats; the dwellinghouse is 1(b) and 1(c). Getting those two the wrong way round changes almost every figure in the row.

Approved Document B Appendix B Table B2, minimum periods of fire resistance in minutes
Purpose group (Table B2 row)	Basement more than 10 m deep	Basement up to 10 m	Top floor up to 5 m	Up to 11 m	Up to 18 m	Up to 30 m	More than 30 m
1(a) Block of flats, without sprinkler system	90	60	30 †	60 + §	Not permitted (2)	Not permitted (2)	Not permitted (2)
1(a) Block of flats, with sprinkler system (3)	90	60	30 †	60 + §	60 + §	90 +	120 +
1(b) and 1(c) Dwellinghouse	Not applicable (4)	30 * †	30 †	60 (5)	60 (5)	Not applicable (4)	Not applicable (4)
2(a) Residential: institutional	90	60	30 †	60	60	90	120 ‡
2(b) Residential: other	90	60	30 †	60	60	90	120 ‡
3 Office, without sprinkler system	90	60	30 †	60	60	90	Not permitted (6)
3 Office, with sprinkler system (3)	60	60	30 †	30 †	30 †	60	120 ‡
4 Shop and commercial, without sprinkler system	90	60	60	60	60	90	Not permitted (6)
4 Shop and commercial, with sprinkler system (3)	60	60	30 †	60	60	60	120 ‡
5 Assembly and recreation, without sprinkler system	90	60	60	60	60	90	Not permitted (6)
5 Assembly and recreation, with sprinkler system (3)	60	60	30 †	60	60	60	120 ‡
6 Industrial, without sprinkler system	120	90	60	90	90	120	Not permitted (6)
6 Industrial, with sprinkler system (3)	90	60	30 †	60	60	90	120 ‡
7(a) Storage and other non-residential, without sprinkler system	120	90	60	90	90	120	Not permitted (6)
7(a) Storage and other non-residential, with sprinkler system (3)	90	60	30 †	60	60	90	120 ‡
7(b)(i) Open sided car park for light vehicles (7)	Not applicable	Not applicable	15 † #	15 † # (8)	15 † # (8)	15 † # (8)	60
7(b)(ii) Any other car park for light vehicles	90	60	30 †	60	60	90	120 ‡

All figures are minutes. The purpose group name in the first column is the name Table B2 itself gives the row. Where a row is split into a “without sprinkler system” and a “with sprinkler system” line, both lines are shown, because reading the wrong one is the commonest way to arrive at a period that is too short: a block of flats above 11m has no unsprinklered line at all.

The Table B2 Notes That Change the Figure

The symbols and numbers in the cells above are not decoration. Several of them move the period, and two of them remove it. These are quoted from the notes printed under Table B2.

Notes printed under Approved Document B Table B2
Marker	What the note says
(no marker)	“For single storey buildings, the periods under the heading ‘Up to 5’ apply. If single storey buildings have basements, for the basement storeys the period appropriate to their depth applies.”
*	“For the floor over a basement or, if there is more than one basement, the floor over the topmost basement, the higher of the period for the basement storey and the period for the ground or upper storey applies.”
†	“For compartment walls that separate buildings, the period is increased to a minimum of 60 minutes.” This is about walls between separate buildings and it applies to every purpose group carrying the marker. It is not a 60 minute floor for flats.
+	“For any floor that does not contribute to the support of the building within a flat of more than one storey, the period is reduced to 30 minutes.”
§	“For flat conversions, refer to paragraphs 6.5 to 6.7 regarding the acceptability of 30 minutes.”
‡	“For elements that do not form part of the structural frame, the period is reduced to 90 minutes.”
#	“For elements that protect the means of escape, the period is increased to 30 minutes.”
1	“Refer to note 1, Table B1 for the specific provisions of test.”
2	“Blocks of flats with a top storey more than 11m above ground level (see Diagram D6) should be fitted with a sprinkler system in accordance with Appendix E.” The note adds that sprinklers should be provided within the individual flats and do not need to be provided in common areas such as stairs, corridors or landings when those areas are fire sterile.
3	“‘With sprinkler system’ means that the building is fitted throughout with an automatic sprinkler system in accordance with Appendix E.”
4	“Very large (with a top storey more than 18m above ground level or with a 10m deep basement) or unusual dwellinghouses are outside the scope of the guidance provided with regard to dwellinghouses.”
5	“A minimum of 30 minutes in the case of three storey dwellinghouses, increased to 60 minutes minimum for compartment walls separating buildings.”
6	“Buildings within the ‘office’, ‘shop and commercial’, ‘assembly and recreation’, ‘industrial’ and ‘storage and other non-residential’ (except car parks for light vehicles) purpose groups (purpose groups 3 to 7(a)) require sprinklers where there is a top storey more than 30m above ground level.”
7	“The car park should comply with the relevant provisions in the guidance on requirement B3, Section 11 of Approved Document B Volume 2.”
8	Certain steel elements are deemed to satisfy the 15 minute minimum when tested to the European test method: beams supporting concrete floors at a maximum Hp/A of 230 m^-1, free-standing columns at a maximum 180 m^-1 and wind bracing and struts at a maximum 210 m^-1, all under full design load. Guidance is also available in BS EN 1993-1-2.

Note 5 is the one most often skipped. The dwellinghouse cells at “Up to 11” and “Up to 18” print 60 minutes, but note 5 relaxes that to a minimum of 30 minutes for three storey dwellinghouses, holding 60 minutes only for compartment walls separating buildings. Note 5 is attached to those two cells and nowhere else.

Why a House Above 18 m Has No Period

Table B2 rows 1(b) and 1(c) print Not applicable, not a number, in the “Up to 30” column, the “More than 30” column and the basement column for a lowest basement more than 10m deep. Note 4 gives the reason: a very large dwellinghouse, meaning one with a top storey more than 18m above ground level or with a 10m deep basement, and an unusual dwellinghouse, are outside the scope of the guidance provided with regard to dwellinghouses.

There is therefore no Approved Document period for that building, and any figure presented as one has been invented. Take the design to a fire engineer, normally working to BS 9991, and agree the strategy with your building control body. Note that a tall block of flatsis a different purpose group, 1(a), and does have figures: 90 minutes at “Up to 30” and 120 minutes at “More than 30”, both on the sprinklered line, because note 2 makes sprinklers mandatory in a block of flats with a top storey more than 11m above ground level.

Fire Resistance by Element (AD B Appendix B, Table B1)

Table B1 says which criteria each element has to meet and for how long. Most rows point back at Table B2 for the period; the rows that carry their own number do not scale with the height of the building. The letters are defined in Table B1 note 1: R is loadbearing capacity, E is integrity, I is insulation.

Approved Document B Appendix B Table B1, specific provisions of the test for fire resistance of elements of structure
Item	Part of building	Minimum provision, European classification	Type of exposure
1	Structural frame, beam or column	R, see Table B2	Exposed faces
2	Loadbearing wall. For a wall also described in any of the following items, the more onerous guidance should be applied	R, see Table B2	Each side separately
3(a)	Floor between a shop and a flat above	REI 60 or see Table B2, whichever is greater	From underside
3(b)	Floor in the upper storey of a two storey dwellinghouse, but not over a garage or basement	R 30 and EI 15	From underside
3(c)	Any other floor, including compartment floors	REI, see Table B2	From underside
4(a)	Any part of a roof forming an escape route	REI 30	From underside
4(b)	Any roof that performs the function of a floor	REI, see Table B2	From underside
5(a)	External wall, any part a maximum of 1000 mm from any point on the relevant boundary	REI, see Table B2	Each side separately
5(b)	External wall, any part a minimum of 1000 mm from the relevant boundary	RE see Table B2, and I 15	From inside the building
5(c)	External wall, any part beside an external escape route	RE 30	From inside the building
6(a)	Compartment wall separating a flat from any other part of the building (para 7.1)	REI 60 or see Table B2, whichever is less	Each side separately
6(b)	Compartment wall separating occupancies	REI 60 or see Table B2, whichever is less	Each side separately
7	Compartment walls other than in item 6 or item 10	REI, see Table B2	Each side separately
8(a)	Protected shaft, excluding any firefighting shaft: any glazing described in Section 7 Diagram 7.2	E 30	Each side separately
8(b)	Any other part between the shaft and a protected lobby or corridor described in Section 7 Diagram 7.2	REI 30	Each side separately
8(c)	Any part of a protected shaft not described in 8(a) or 8(b)	REI, see Table B2	Each side separately
9(a)	Enclosure to a protected stairway, where it does not form part of a compartment wall or a protected shaft	REI 30	Each side separately
9(b)	Enclosure to a lift shaft, on the same condition	REI 30	Each side separately
10	Wall or floor separating an attached or integral garage from a dwellinghouse	REI 30	From garage side
11	Fire resisting construction in dwellinghouses not described elsewhere	REI 30	Each side separately
12	Firefighting shafts	REI 120	From side remote from shaft
12(a)	Construction separating a firefighting shaft from the rest of the building	REI 60	From shaft side
12(b)	Construction separating firefighting stair, firefighting lift shaft and firefighting lobby	REI 60	Each side separately
13(a)	Enclosure to a protected lobby, where it is not a compartment wall or described in item 8	REI 30	Each side separately
13(b)	Enclosure to a protected corridor, on the same condition	REI 30	Each side separately
14	Sub-division of a corridor	REI 30	Each side separately

Three rows are worth reading twice. Item 9(a) fixes the enclosure to a protected stairway at REI 30, and it does not rise with the height of the building; where those same walls are also a compartment wall or a protected shaft, items 6, 7 or 8 apply instead and those do point at Table B2. Item 6(a) is a cap and not a floor: a compartment wall separating a flat from any other part of the building is REI 60 or Table B2, whichever is less, so in a block of flats with a top floor up to 5m it is REI 30, because Table B2 gives 30 there. And item 3(b) gives the upper floor of a two storey dwellinghouse R 30 and EI 15, which is a lower insulation period than the REI 30 usually assumed.

Table B1 note 1 also warns that the national BS 476 classifications do not automatically equate with the European classifications, so a product cannot be assumed to hold a European class unless it has been tested to it. Para B23 names the three tables and what each one does: “Table B1 gives the specific requirements for each element of structure. Table B2 sets out the minimum periods of fire resistance for elements of structure. Table B3 sets out limitations on the use of uninsulated fire resisting glazed elements.” So Table B3 exists, but it is the glazing table on escape routes, not a table of periods, and there is no Table A1 or Table A2 in this edition at all: Appendix A is Key terms. The Table A2 numbering belongs to the 2006 and 2013 editions and Table B4 to the 2019 edition incorporating the 2020 and 2022 amendments.

Fire Doorset Provisions (AD B Appendix C, Table C1)

Doorset ratings come from Table C1, not from the period of the surrounding construction, so they are frequently a different number from the wall the door sits in. Para C13 states the link explicitly: the performance of some doorsets in Table C1 is tied to the minimum periods for elements of structure in Tables B1 and B2, and limitations on uninsulated glazing in fire doorsets are given in Table B3.

Approved Document B Appendix C Table C1, provisions for fire doorsets
Item	Position of door	Minimum integrity, European standard	Alternative, BS 476-22
1	In a compartment wall separating buildings	Same as for the wall in which the door is fitted, but a minimum of 60 minutes	Same, minimum 60 minutes
2(a)	In a compartment wall, if it separates a flat from a space in common use. This is the flat entrance door	E 30 S_a	FD 30 S
2(b)	Enclosing a protected shaft forming a stairway wholly or partly above the adjoining ground, in a building used for flats, other residential, assembly and recreation, or office purposes	E 30 S_a	FD 30 S
2(c)	Enclosing a protected shaft forming a stairway not described in 2(b)	Half the period of the wall it is fitted in, but 30 minutes minimum, with suffix S_a	Half, 30 minutes minimum, suffix S
2(d)	Enclosing a protected shaft forming a lift or service shaft	Half the period of the wall it is fitted in, but 30 minutes minimum	Half, 30 minutes minimum
2(e)	In a compartment wall, not described in 2(a) to 2(d)	Same as for the wall in which it is fitted, adding S_a only if the door is used for progressive horizontal evacuation under the guidance to requirement B1	Same as the wall, adding S on the same condition
3	In a compartment floor	Same as for the floor in which it is fitted	Same as the floor
4(a)	Forming part of the enclosures of a protected stairway, except as described in item 9 or 11(b)	E 30 S_a	FD 30 S
4(b)	A lift shaft (para 3.99b) that does not form a protected shaft in 2(b), 2(c) or 2(d)	E 30	FD 30
5(a)	Forming part of the enclosure of a protected lobby approach, or protected corridor, to a stairway	E 30 S_a	FD 30 S
5(b)	Any other protected corridor	E 20 S_a	FD 20 S
5(c)	A protected lobby approach to a lift shaft (paras 3.102 to 3.104)	E 30 S_a	FD 30 S
6	Giving access to an external escape route	E 30	FD 30
7(a)	Sub-dividing corridors connecting alternative exits	E 20 S_a	FD 20 S
7(b)	Sub-dividing dead-end portions of corridors from the remainder of the corridor	E 20 S_a	FD 20 S
8	Any door within a cavity barrier	E 30	FD 30
9	Any door forming part of the enclosure to a protected entrance hall or protected landing in a flat	E 20	FD 20
10(a)	Any door forming part of the enclosure to a place of special fire hazard	E 30	FD 30
10(b)	Any door forming part of the enclosure to ancillary accommodation in care homes (para 2.44, AD B Volume 2)	E 30	FD 30
11(a)	In a dwellinghouse, between a dwellinghouse and a garage	E 30 S_a	FD 30 S
11(b)	Forming part of the enclosures to a protected stairway in a single family dwellinghouse	E 20	FD 20
11(c)	Within any fire resisting construction in a dwellinghouse not described elsewhere in Table C1	E 20	FD 20

Self-closers. Appendix C5: all fire doorsets, including to flat entrances and between a dwellinghouse and an integral garage, should be fitted with a self-closing device, except fire doorsets to cupboards, fire doorsets to service ducts normally locked shut, and fire doorsets within flats and dwellinghouses. So the garage door is expressly named as one that must self-close, while the doors on a protected stairway inside a single family dwellinghouse are not.

The S_a suffix. Table C1 note 2: unless pressurisation techniques complying with BS EN 12101-6 are used, these doors should either have a leakage rate not exceeding 3 m³/m/hour from head and jambs only when tested at 25 Pa under BS 476-31.1, or meet the additional S_aclassification when tested to BS EN 1634-3. The suffix is not attached to every fire door: Table C1 leaves it off items 3, 4(b), 6, 8, 9, 10(a), 10(b), 11(b) and 11(c), and on item 2(e) it applies only where the door serves progressive horizontal evacuation.

FD 20 in practice. FD 20 doorsets are no longer manufactured or third-party certified, so an FD 30 door is normally fitted where Table C1 asks for E 20. Fitting the higher-rated door satisfies the requirement; it does not mean the requirement was 30 minutes.

Version note.The Table C1 above carries the banner “Effective until 29 September 2026”. The 2026 amendment, effective from 30 September 2026, adds the words “or an evacuation shaft” to items 2(b), 2(c), 4(a) and 5(a). None of the ratings in the table change.

Scotland, Wales and Northern Ireland

Approved Document B applies in England. Scotland uses the Building (Scotland) Regulations Technical Handbooks, Section 2 (Fire), which set out their own classifications and tables rather than Tables B1, B2 and C1. Wales has its own Approved Document B, which has diverged from the England version. Northern Ireland uses Technical Booklet E, which is broadly similar to Approved Document B but may sit on a different edition date. Check the document for the jurisdiction the building is in.

Related Calculators

The Part B Fire Calculator performs this same Table B2 lookup for a given purpose group, height and basement depth, and returns the out of scope result rather than a period where Table B2 reads “Not applicable”. Use the Fire Resistance Wall Calculator to specify wall constructions for a required rating, or the Fire Stopping Calculator for penetrations through compartmentation.

Figures on this page were read from the rendered pages of the Approved Document B Volume 1 PDF on gov.uk, 2019 edition incorporating the 2020, 2022 and 2025 amendments, collated with the 2026 and 2029 amendments. Table B2 carries the banner “Effective until 1 September 2029”; a 2029 amendment version of it is printed later in the same document. Approved Documents are updated periodically, so check the current edition on gov.uk before relying on any figure for a live project.