ProjectCalcThree standards, three different problems
The words "damp" and "damp-proofing" cover at least three distinct problems, and Approved Document C names a different standard for each:
| Standard | Title as cited in the approved document | The problem it addresses |
|---|---|---|
| BS 8215:1991 | Code of practice for design and installation of damp-proof courses in masonry construction | Damp-proof courses in walls — the 150 mm height and 225 mm cavity rules sit in a detail code that also covers installation. |
| BS 8102:1990 | Code of practice for protection of structures against water from the ground | Water arriving from the ground under pressure — basements and below-ground structures, which the standard diagrams do not cover. |
| BS 5250:2002 | Code of practice for the control of condensation in buildings | Condensation — vapour moving through the construction and condensing where it should not. |
| BS EN ISO 13788:2002 | Hygrothermal performance of building components and building elements (cited alongside BS 5250) | The method used to assess the risk of interstitial condensation. |
How the approved document uses them
Part C does not present these standards as optional background. Its structure is a technical solution followed by an alternative approach, and the standards are the alternative route:
- On walls, the alternative approach is stated plainly: the requirement can also be met by following the relevant recommendations of Clauses 4 and 5 of BS 8215:1991, together with BS 8102:1990.
- Protection of structures against water from the ground is also sourced to BS 8102 and, for background, to BS CP 102.
- On floors exposed from below — where interstitial condensation is the risk — the design is sent to Clause 8.5 and Appendix D of BS 5250:2002, to BS EN ISO 13788:2002 and to BR 262.
- The document refers separately to Clause 8.3 of BS 5250:2002 in its wall provisions.
Why the distinction matters on a real job
Choosing the wrong one wastes money in a way that is hard to see.
- A damp-proof course is not a tanking system. A DPC deals with moisture rising through masonry by capillary action; BS 8102 territory is water arriving under pressure on a below-ground structure. Treating a basement with a DPC detail is a solution to a different problem.
- Condensation is not damp penetration. If the wall is dry to the touch but the corner goes black every winter, the cause is likely to be vapour condensing where it should not — a BS 5250 problem. Adding a damp-proof course will not touch it.
- Getting the order wrong is expensive. A membrane can be defeated by a floor level set too low, or by a ground covering laid without a ventilated air space above it. Those are design decisions taken before the materials arrive.
The numbers themselves — a damp-proof course at least 150 mm above adjoining ground, a cavity taken down at least 225 mm below the lowest damp-proof course with weep holes every 900 mm — are set out on our Approved Document C page with their paragraph references.
A note on editions
The editions in the table above are the ones cited by Approved Document C — that is the citation the regulation rests on, and it is why they are the editions named there. Three of them are still current exactly as cited: BS 8215:1991, BS 8104:1992 and CP 102:1973. The rest have moved on. The current editions, read from the BSI catalogue on 22 September 2026, are BS 8102:2022 (title now Protection of below ground structures against water ingress), BS 5250:2021 (title now Management of moisture in buildings) and BS EN ISO 13788:2012. Cite the current edition when you specify; cite the approved document when you are explaining why the rule exists.
Edition status — what the approved document cites, and what is current
An approved document names the edition of a standard that existed when it was written. That edition is not necessarily the current one. The table below sets out, for every standard this page relies on, the title as published, the edition the approved document cites, and the edition BSI catalogues today (22 September 2026). Where the cited edition is withdrawn, the page says so; where we could not confirm the replacement, no current edition is stated.
| Standard | Title as published | Edition cited by the approved document | Current edition (BSI) |
|---|---|---|---|
| BS 8215 | Code of practice for design and installation of damp-proof courses in masonry construction | BS 8215:1991 — cited by Approved Document C | BS 8215:1991 — Current (28 February 1991) |
| BS 8102 | Protection of below ground structures against water ingress. Code of practice | BS 8102:1990 — cited by Approved Document C as "Code of practice for protection of structures against water from the ground" | BS 8102:2022 — Current (31 March 2022). Note the title has changed as well as the edition |
| BS 5250 | Management of moisture in buildings. Code of practice | BS 5250:2002 — cited by Approved Document C as "Code of practice for the control of condensation in buildings" | BS 5250:2021 — Current |
| BS EN ISO 13788 | Hygrothermal performance of building components and building elements — Internal surface temperature to avoid critical surface humidity and interstitial condensation. Calculation methods | BS EN ISO 13788:2002 — cited by Approved Document C | BS EN ISO 13788:2012 — Current |
| BS 8104 | Code of practice for assessing exposure of walls to wind-driven rain | BS 8104:1992 — cited by Approved Document C | BS 8104:1992 — Current, Under Review |
| BS CP 102 | Code of practice for protection of buildings against water from the ground | BS CP 102:1973 — cited by Approved Document C | CP 102:1973 — Current (catalogued without the BS prefix) |
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 C: Site preparation and resistance to contaminants and moisture, 2013 edition — references to BS 8215:1991, BS 8102:1990, BS 5250:2002 and BS EN ISO 13788:2002 (paragraphs 4.21, 5.6 and related provisions) — GOV.UK publications, "Site preparation and resistance to contaminants and moisture: Approved Document C", 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.