Part E
Approved Document E: Resistance to the Passage of Sound
The part of the Building Regulations covering resistance to the passage of sound, setting sound insulation standards mainly between dwellings and for separating walls and floors. It is most relevant to conversions and new separating elements.
Also known as
Part EApproved Document EAD EResistance to Sound
What Part E requires for a home project
The Part E requirements and terms the buildwiz guides rely on, with paragraph references where the document gives one. Check the current edition on gov.uk before you build to it.
Limits and figures
- Internal floor type C: minimum floor surface mass
- Approved Document E Section 5 internal floor type C (Diagram 5.7): a floor surface of timber or wood-based board with a minimum mass per unit area of 15 kg/m². It is one of three type C figures (surface, ceiling, mineral wool) and is the offered recipe for a new internal timber joist floor, not a stand-alone requirement. Section 5 is headed 'Internal walls and floors for new buildings'; building control decides how it applies to a loft floor.
- Internal floor type C: minimum mineral wool thickness
- Approved Document E Section 5 internal floor type C (Diagram 5.7): an absorbent layer of mineral wool laid in the floor cavity with a minimum thickness of 100mm and a minimum density of 10 kg/m³. The density is held in the part-e-acoustic-mineral-wool-density-minimum GuidanceValue. The 100mm needs room in the joist depth, which is one reason new loft joists are deeper than the old ceiling joists.
- Internal floor type C: minimum plasterboard ceiling mass
- Approved Document E Section 5 internal floor type C (Diagram 5.7): a ceiling of a single layer of plasterboard with a minimum mass per unit area of 10 kg/m², fixed by any normal method. This is a sound-insulation figure. The separate 30-minute fire-resisting ceiling under the loft floor is normally heavier, so do not equate the two.
- New internal floor airborne sound insulation (laboratory value)
- Approved Document E Table 0.2 gives a minimum laboratory airborne sound insulation of 40 dB Rw for new internal floors within dwelling-houses (new internal walls also 40 dB Rw). May apply to the new loft floor (building control confirms how Requirement E2 applies); the wall between a bedroom and its en suite WC is excluded from E2.
- Separating wall types 1.1/1.2 minimum mass per unit area
- Approved Document E paragraphs 2.33 and 2.34 specify at least 415 kg/m² surface mass for the complete separating-wall examples 1.1 and 1.2. This is not a universal separating-wall minimum: other approved constructions have different specifications. Calculate the complete construction's mass and acoustic performance; do not assume 140mm blockwork achieves this figure.
- Separating-wall back-box minimum offset
- Approved Document E (Resistance to the passage of sound) says not to place electrical sockets back to back on a separating wall between dwellings and to stagger them; on a masonry separating wall it also advises against deep sockets and chases. For a timber-frame separating wall it recommends a minimum edge-to-edge stagger of 150 mm. Staggering avoids a sound short-circuit through the wall at the boxes. Affects party walls in semi-detached extensions and any new opening through a separating wall.
Terms explained
- Back Boxes (Metal)
- Galvanised steel boxes recessed into the wall to house the wiring connections behind socket and switch faceplates. Available from 16mm to 47mm deep. Standard-profile sockets, switches and dimmers fit a 25mm box; USB sockets, cooker switches and slim or screwless faceplates need 35mm, and smart modules 47mm. Must be earthed.
- Concrete Blocks 140mm
- Wider concrete blocks used where additional structural strength or wall thickness is required, common in foundation walls and below DPC level.
- Flooring Underlay
- A thin cushioning layer laid between the subfloor and a floating floor covering to provide acoustic dampening, thermal insulation, and a level surface. Type depends on the floor finish and substrate: foam or cork for laminate and engineered wood; specific thin-profile or self-adhesive types for LVT. Over underfloor heating, the floor covering and underlay together must stay within the heating maker's thermal resistance limit, commonly 0.15 m²K/W (1.5 tog). An underlay the floor maker does not approve can void the floor's warranty.
- Internal floor type C (timber joist)
- The Approved Document E Section 5 example construction for a new internal timber or metal joist floor: a wood-based floor surface, a plasterboard ceiling and an absorbent mineral wool layer in the cavity. It is an example that meets the 40 dB Rw laboratory value, not a mandatory recipe. Section 5 is headed 'for new buildings', so whether building control applies it to a loft floor is its call; treat it as the usual route. The 100mm of mineral wool is one reason the new joists are deeper than the old.
- Mineral Wool Insulation 100mm
- Flexible mineral fibre insulation in rolls or slabs. Used between timber studs, joists and rafters. Good acoustic properties as well as thermal. Cheaper than PIR but requires greater thickness for equivalent thermal performance. Common brands include Rockwool and Knauf.
- Perimeter Edge Strip
- 10-20mm compressible foam strip installed at room perimeter before screed pour over PIR floor insulation. Allows thermal expansion and prevents cold bridging at wall-floor junction.
- Wall tie
- Austenitic stainless steel connector (Approved Document A para 2C19 requires BS EN 845-1 stainless ties) embedded in the mortar joints of both leaves of a cavity wall, transferring lateral load and stabilising the outer leaf. Spacing and embedment depths are set by NHBC 6.1 and BS EN 845-1; typical spec is 2.5 ties per square metre at 450mm vertical and 900mm horizontal centres, with closer spacing at openings.
Pages where Part E comes up
4 guides reference Part E, grouped by build phase.
Structure
Specification
Second fix
Want the full picture?
The buildwiz build guides walk through a UK extension in sequence and link to Part E (and every other Approved Document) at the exact stage it bites. That is usually a more productive way to use this material than reading the document cover to cover.