Question 1

What are Robust Details?

Accepted Answer

Robust Details (RD) are pre-approved wall and floor constructions published by Robust Details Ltd (www.robustdetails.com) that have been demonstrated through extensive testing to consistently meet Part E without pre-completion testing. Using an RD construction on site means you pay a registration fee but avoid the cost of acoustic testing. There are currently RD specifications for masonry walls, timber-frame walls, concrete floors, and timber floors.

Question 2

What Rw rating should a separating wall achieve?

Accepted Answer

To consistently meet the Part E on-site target of DnT,w + Ctr >= 45 dB (new build), a separating wall should have a laboratory Rw (C; Ctr) rating of at least 53 dB (Rw + Ctr >= 48 dB). The difference accounts for flanking transmission and workmanship on site. Robust Details walls typically achieve Rw + Ctr of 50 dB or more.

Question 3

Can I use a timber stud wall as a separating wall?

Accepted Answer

Yes, but it must be a twin-frame construction with no rigid connections between the two frames. A single timber stud wall will not meet Part E for separating walls between dwellings. Typical compliant timber separating walls use two independent rows of studs (minimum 60 mm gap) with at least 25 mm mineral wool in each frame and two layers of plasterboard on each face.

Question 4

What floor coverings help meet impact sound requirements?

Accepted Answer

A resilient floor covering or floating floor is essential for meeting the impact sound requirement of L'nT,w <= 62 dB for new builds (64 dB for conversions). Options include: a floating screed on resilient layer (18 mm minimum), a floating chipboard platform on mineral wool (e.g. 19 mm T&G chipboard on 25 mm mineral wool), or a proprietary acoustic mat under hard floor finishes. Carpet with underlay may also suffice on concrete floors.

Wall Type	Construction	Typical Rw (dB)	AD-E Reference
Type 1 — Solid masonry	Dense block (min. 375 kg/m² mass), 13 mm plaster each side	53-56	Section 1, E-WT-1
Type 2 — Cavity masonry	Two leaves of block with 75 mm cavity, butterfly ties, plaster finish	55-58	Section 1, E-WT-2
Type 3 — Masonry between IWL	Dense or lightweight block with independent wall linings (IWL) each side	55-60	Section 1, E-WT-3
Type 4 — Timber/steel frame	Twin independent frames, min. 200 mm total depth, mineral wool, 2 x plasterboard each face	55-62	Section 1, E-WT-4

Floor Type	Construction	Airborne Rw (dB)	Impact Ln,w (dB)
Type 1 — Concrete with soft covering	Concrete slab min. 300 kg/m², resilient covering (carpet + underlay)	52-55	60-65
Type 2 — Concrete with floating floor	Concrete slab with floating screed or platform on resilient layer	55-58	52-58
Type 3 — Timber with ceiling treatment	Timber joists with mineral wool, floating platform, independent ceiling	50-55	55-62
Type 3.1 — Engineered timber joist	I-joists or metal web with enhanced ceiling, floating floor	52-57	52-58

RD Type	Element	Description
E-WM-1 to E-WM-24	Masonry separating walls	Various block types, cavity/solid, wet/dry lining
E-WT-1 to E-WT-8	Timber frame separating walls	Twin frame with board linings
E-FC-1 to E-FC-14	Concrete separating floors	Various concrete types with ceiling and floor treatments
E-FT-1 to E-FT-6	Timber separating floors	Timber joist with floating floor and independent ceiling

Part E Wall & Floor Sound Reduction

Separating Wall Types (AD-E Section 1)

Separating Floor Types (AD-E Section 2)

Robust Details — Current Types

Scotland & Northern Ireland

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Frequently Asked Questions

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Part E Acoustic Ratings

Part B Fire Resistance Ratings

UK Cavity Tray Sizes

Part L 2021 U-Value Targets

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