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Fire Resistance Calculator
Determine the minimum fire resistance period for structural and separating elements per Approved Document B. Looks up Appendix B, Table B2 requirements by building height, purpose group and element type.
Height of the topmost floor above ground level
Elements requiring fire protection
Indicative fire-protection cost per element
Safety notice
Fire safety measures must satisfy Approved Document B and often need building control approval. Confirm the final specification with building control or a fire engineer before relying on it.
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How We Calculate This
This calculator looks up the minimum fire resistance period from Approved Document B, Appendix B, Table B2 (the same table in AD B Vol 1 for flats and Vol 2 for other buildings, 2019 edition incorporating the 2020, 2022 and 2025 amendments — the live document as of 2026). The 2025 amendment renumbered this periods table from "Table B4" to "Table B2"; the values are unchanged.
The lookup
Period = f(purpose group, top-floor height, sprinklers, basement depth)
Unsprinklered ground/upper-storey periods by Table B2 height band:
- Block of flats: 30 min (≤5m), 60 min (≤11m); above 11m a sprinkler system is mandatory (Note 2) — then 60 min (≤18m), 90 min (≤30m), 120 min (>30m)
- Office: 30 min (≤5m), 60 min (≤11m and ≤18m), 90 min (≤30m); over 30m requires sprinklers (Note 6)
- Shop / commercial and Assembly / recreation: 60 min (≤5m to ≤18m), 90 min (≤30m); over 30m requires sprinklers
- Industrial and Storage: 60 min (≤5m), 90 min (≤11m and ≤18m), 120 min (≤30m); over 30m requires sprinklers
- Basements (keyed to basement depth, not building height): 60 min (≤10m deep) and 90 min (>10m) for most groups; 90 min (≤10m) and 120 min (>10m) for industrial / storage
The floor over a basement takes the higher of the basement period and the storey period (Table B2 note *). Sprinklers are modelled as the alternate Table B2 column, not a blanket 30-minute reduction. Performance criteria (R / E / I) follow Table B1 and depend on whether the element carries load.
This is a planning-stage guide. Confirm the period, sprinkler obligations and any project-specific provisions with a competent fire engineer and your building control body.
Frequently Asked Questions
The minimum period is read from Approved Document B, Appendix B, Table B2, using the building's purpose group (block of flats, office, shop, assembly, industrial, storage), the height of the topmost floor above ground, whether a sprinkler system is fitted, and — for below-ground elements — the depth of the lowest basement. Periods are 30, 60, 90 or 120 minutes. (This table was numbered 'Table B4' in the 2019 edition incorporating the 2020 and 2022 amendments; the 2025 amendment renumbered it to Table B2 — the period values are unchanged.)
R = loadbearing capacity (resistance to collapse), E = integrity (resistance to fire penetration), I = insulation (resistance to heat transfer), per AD B Table B1 (the test-criteria table, numbered Table B3 before the 2025 amendment). A beam or column needs R only. A non-loadbearing separating element (e.g. a non-loadbearing compartment wall) needs EI. A loadbearing separating element — a compartment wall, compartment floor or floor that also carries load — needs REI. The number (e.g. REI 60) is the period in minutes.
Yes. Table B2 uses height bands for the top floor above ground: up to 5m, up to 11m, up to 18m, up to 30m, and more than 30m. For offices the unsprinklered periods are 30 / 60 / 60 / 90 minutes, with over-30m not permitted without sprinklers. Shops and assembly/recreation are 60 minutes up to 18m, then 90 minutes up to 30m. Industrial and storage are 60 minutes up to 5m, 90 minutes up to 18m, then 120 minutes up to 30m (they do not jump straight to 120). A block of flats is 30 minutes up to 5m and 60 minutes up to 11m — and above 11m a sprinkler system becomes mandatory (Note 2). Basements are keyed to their own depth: for most groups 60 minutes up to 10m deep and 90 minutes over 10m; for industrial and storage 90 minutes up to 10m and 120 minutes over 10m.
Sprinklers are not a flat "minus 30 minutes" discount. Table B2 has a separate sprinklered column with its own values — sometimes lower (a sprinklered office up to 18m drops from 60 to 30 minutes), sometimes the same (a sprinklered shop up to 18m stays 60). Crucially, sprinklers are mandatory in some cases: a block of flats with a top storey above 11m (Note 2) and any office/shop/assembly/industrial/storage building above 30m (Note 6) must be sprinklered — without them those heights are "Not permitted" under Table B2, not simply a higher number.
Fire resistance is demonstrated by testing or assessment to BS EN 1363/1364/1365/1366 with classification to BS EN 13501-2 (the system AD B now uses), or to the legacy BS 476 Parts 20-24. Products must hold a valid test certificate or assessment. Common systems include fire-rated plasterboard, intumescent coatings and concrete encasement.
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Last updated: June 2026
Verified against UK standards · estimates only, confirm with your supplier.