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This is Approved Document B, Volume 1: Dwellings — the 2019 edition incorporating the 2020, 2022, 2025 and 2026 amendments, marked "for use in England". It covers Requirements B1 to B5: means of warning and escape, internal fire spread (linings), internal fire spread (structure), external fire spread, and access and facilities for the fire service.
Wall and ceiling linings — the classes
Requirement B2 is about the surface of walls and ceilings: how quickly a lining lets fire spread across it. Linings are classified by European reaction-to-fire class, written as three parts — the main class, then smoke (s) and droplets (d) — such as C-s3, d2. Table 4.1 sets the classification by location.
| Location | Classification |
|---|---|
| Small rooms of maximum internal floor area 4 m²; garages (as part of a dwellinghouse) of maximum internal floor area 40 m² | D-s3, d2 |
| Other rooms (including garages) | C-s3, d2 |
| Circulation spaces within a dwelling | B-s3, d2 |
| Other circulation spaces (including the common areas of blocks of flats) | B-s3, d2 |
Two points that catch people out. First, a small percentage of a wall may be of lower performance than the table requires, but no worse than class D-s3, d2, and the total area of lower-performance lining in any one room is limited. Second, there is a specific allowance for wallcoverings: wallcoverings conforming to BS EN 15102 that achieve at least class C-s3, d2 and are bonded to a class A2-s3, d2 substrate are acceptable.
The document also defines what counts as a wall for these purposes: it includes the internal surface of internal and external glazing (except glazing in doors) and any part of a ceiling sloping at more than 70 degrees to the horizontal, but excludes doors and door frames, window frames, architraves, picture rails, skirtings and similar narrow members, and fireplace surrounds and fitted furniture.
Fire resistance: what the ratings look like
Houses and flats are protected by construction that holds fire back for a period, expressed as a rating — REI 30 for load-bearing elements such as a protected stairway enclosure, and E 20 for a fire doorset. Those two figures appear throughout Volume 1: a protected stairway is "a stair separated by fire resisting construction (minimum REI 30)" with fire doorsets of "minimum E 20". The same REI 30 standard is applied to walls and partitions that separate a dwellinghouse from an attached garage, and to the enclosure to a loft conversion's escape route.
External walls near a boundary
Requirement B4 deals with external fire spread. The rule for a wall on, or within 1,000 mm of, the relevant boundary is:
- unprotected areas of the wall must meet the conditions in Diagram 11.5, and the rest of the wall must be fire resisting from both sides;
- external surface materials facing the boundary must be class B-s3, d2 or better.
Once a wall is 1,000 mm or more from the relevant boundary, the rest of the wall (if any) need only be fire resisting from the inside.
Roof coverings and the boundary
Section 12 and Table 12.1 limit roof coverings by their designation and their distance from any point on the relevant boundary. The designations run from BROOF(t4) down to FROOF(t4). BROOF(t4) coverings are acceptable at any distance from the boundary; the lower designations are not acceptable within 6 metres, and the very lowest are restricted further out.
| Designation of covering | Less than 6 m | At least 6 m | At least 12 m | At least 20 m |
|---|---|---|---|---|
| BROOF(t4) | Acceptable | Acceptable | Acceptable | Acceptable |
| CROOF(t4) | Acceptable | Acceptable | Acceptable | Acceptable |
| DROOF(t4) | Not acceptable | Acceptable | Acceptable | Acceptable |
| EROOF(t4) | Not acceptable | Acceptable | Acceptable | Acceptable |
| FROOF(t4) | Not acceptable | Not acceptable | Acceptable | Acceptable |
The notes to the table carry two things worth knowing: separation distances do not apply to the boundary between the roofs of a pair of semi-detached dwellinghouses or to enclosed or covered walkways; and polycarbonate and uPVC rooflights that achieve a class C-s3, d2 rating by test may be regarded as having a BROOF(t4) designation.
The editions this document cites
These are British and European standards this approved document names. The edition column is the one the document itself cites; the last column is what BSI catalogues today (22 September 2026). Where the two differ, the document is citing an edition that has since been replaced or withdrawn — that is normal for an approved document, and it is why the current edition is listed beside it rather than instead of it.
| Standard | Title as published | Edition cited by the approved document | Current edition (BSI) |
|---|---|---|---|
| BS EN 13501-1 | Fire classification of construction products and building elements — Classification using data from reaction to fire tests | BS EN 13501-1 — cited by Approved Document B with no edition given | BS EN 13501-1:2018 — Current (as BS EN 13501-1:2018 - TC, 31 January 2019). BS EN 13501-1:2007+A1:2009 is Withdrawn |
| BS EN 15102 | Decorative wallcoverings. Roll form | BS EN 15102 — cited by Approved Document B with no edition given | BS EN 15102:2019 — Current (30 June 2019). BS EN 15102:2007+A1:2011 is Withdrawn |
Source: BSI catalogue records read at knowledge.bsigroup.com on 22 September 2026. Each title, designation, status and date in the last two columns was read from the BSI catalogue page for that standard.
Last verified 22 September 2026. Every requirement quoted on this page was read from the primary source listed below on that date, not from a summary. If a figure could not be confirmed in the primary source it is not on this page.
Where these figures come from
- Approved Document B: Fire safety, Volume 1: Dwellings — 2019 edition incorporating 2020, 2022, 2025 and 2026 amendments, for use in England (Requirements B1-B5; Table 4.1; paragraphs 11.8-11.9; Table 12.1) — GOV.UK publications, "Fire safety: Approved Document B", checked 22 September 2026.
- BSI catalogue (“BSI Knowledge”) — product record for each standard listed above: title, current edition and status — knowledge.bsigroup.com, checked 22 September 2026.
Guidance only, not advice
This page is a plain-English summary of published regulations and standards, written to help you plan a job. It is not professional advice, it is not a substitute for the actual document, and it is not a building-control decision.
Building regulations are enforced by your local authority (or an approved inspector) and the facts of a particular job can change the answer. Confirm with your local building control before you start work, and where a job is structural, get it designed by a suitably qualified person. If this page and the source document disagree, the source document wins.