ProjectCalcThe performance standards
Approved Document E (2015 edition) requires separating walls, separating floors and stairs that have a separating function to achieve the values in Table 0.1a for dwelling-houses and flats. Two quantities are used. DnT,w + Ctr is the airborne sound insulation achieved between rooms in the finished building — a minimum, so higher is better. L'nT,w is impact sound insulation — a maximum, so lower is better.
| Building type | Airborne DnT,w + Ctr (minimum) | Impact L′nT,w (maximum) |
|---|---|---|
| Purpose-built — walls | 45 dB | — |
| Purpose-built — floors and stairs | 45 dB | 62 dB |
| Formed by material change of use — walls | 43 dB | — |
| Formed by material change of use — floors and stairs | 43 dB | 64 dB |
So the headline numbers are 45 dB airborne and 62 dB impact for a purpose-built separating floor, relaxing to 43 dB and 64 dB where the building was formed by a material change of use. Rooms for residential purposes have their own table (Table 0.1b): 43 dB for walls, 45 dB airborne and 62 dB impact for floors and stairs when purpose-built, 43 dB and 64 dB after a material change of use.
Internal walls and floors
Table 0.2 covers the constructions inside a dwelling, whether purpose-built or formed by a material change of use. These are laboratory values, expressed as Rw, and are set at a minimum of 40 dB for both walls and floors.
How compliance is shown
Part E is unusual among the Approved Documents in that it is not enough to build something that looks right. Regulations 41 (local authority building control) and 20(1) and (5) (approved inspectors) require appropriate sound insulation testing, and the procedure is the one set out in Annex B of the document. There is one exception: for new-build houses and buildings containing flats, the testing requirement does not apply where the design uses a detail from the set approved and published by Robust Details Ltd, a valid notification is given to the building control body, and the work complies with that detail.
The measurement standards behind the numbers are the BS EN ISO 140 series for measurement and the BS EN ISO 717 series for rating: airborne insulation is rated to BS EN ISO 717-1 and impact sound to BS EN ISO 717-2.
What this means when you are choosing materials
- Impact sound is a flooring problem. The 62 dB maximum is about how much noise a floor transmits downwards when something hits it. The floor finish and any resilient layer are part of that, which is why underlay and carpet specification are not purely cosmetic choices in a flat.
- Airborne sound is a wall and floor problem. Mass, sealing and flanking paths decide it. Filling a gap is worth more than adding a layer.
- Testing versus Robust Details. If the job needs to demonstrate compliance, either route has to be chosen before the build, not after.
- A house is not a flat. The targets apply to separating constructions between dwellings, not to a normal party-free house — but internal walls in any dwelling still carry the 40 dB Rw figure.
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 ISO 717-1 | Acoustics. Rating of sound insulation in buildings and of building elements — Airborne sound insulation | BS EN ISO 717-1:1997 — cited by Approved Document E | BS EN ISO 717-1:2020 — Current, Under Review |
| BS EN ISO 717-2 | Acoustics. Rating of sound insulation in buildings and of building elements — Impact sound insulation | BS EN ISO 717-2:1997 — cited by Approved Document E | BS EN ISO 717-2:2020 — Current, Under Review |
| BS EN ISO 140-3 | Acoustics. Measurement of sound insulation in buildings and of building elements — Laboratory measurement of airborne sound insulation of building elements | BS EN ISO 140-3:1995 — cited by Approved Document E | Not verified in this pass — we checked the status of the cited edition but did not confirm its replacement, so no current edition is stated here |
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 E: Resistance to the passage of sound, 2015 edition (Tables 0.1a, 0.1b and 0.2; paragraphs 0.1-0.3; Annex B) — GOV.UK publications, "Resistance to sound: Approved Document E", 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.