Sound Insulation in Conversions and Refurbishments

What This Requirement Covers

When an existing building is converted to contain new dwellings (e.g., office to flats, house to flats, warehouse to residential), the separating walls and floors between the new dwellings must meet the sound insulation standards in Approved Document E. The requirements for conversions are the same as for new-build dwellings.

Key Requirements

Performance Standards for Conversions

1. Airborne sound insulation (walls and floors): Minimum DnT,w + Ctr of 43 dB (slightly lower than the 45 dB required for new-build, recognising the constraints of existing construction)
2. Impact sound insulation (floors): Maximum L'nT,w of 64 dB (slightly higher than the 62 dB for new-build)

Common Challenges

1. Existing timber floor structures often have poor sound insulation (both airborne and impact)
2. Existing masonry walls may not have sufficient mass or may have gaps that allow sound flanking
3. Existing steel or concrete structures in commercial buildings may transmit structure-borne sound

Upgrade Solutions

Timber floors:

1. Add mass to the ceiling: Two or more layers of plasterboard (15 mm or 19 mm) on resilient bars


2. Add mineral wool absorbent (100 mm minimum) between joists


3. Add a floating floor: 18 mm chipboard on a resilient layer (dense mineral wool or rubber mat) on a platform of 22 mm plywood over the existing floorboards


4. Seal all gaps between the floor and the walls with acoustic sealant

Masonry walls:

1. Add an independent stud frame (minimum 25 mm air gap from the masonry) with mineral wool insulation and two layers of plasterboard


2. Seal all gaps at the perimeter with acoustic sealant


3. Do not bridge the air gap with fixings or services

Concrete floors:

1. Add a floating screed on a resilient layer (25 mm dense mineral wool or closed-cell foam)


2. Add a suspended ceiling with mineral wool and multiple plasterboard layers

Practical Compliance Tips

1. Assess the existing sound insulation performance before designing the conversion; a preliminary sound test can identify the scale of the upgrade needed
2. Budget for significant floor and wall upgrades; achieving the required sound insulation in converted buildings is often more expensive than in new-build
3. Resilient bars and floating floors are critical components; improper installation (hard points, rigid bridges) undermines their effectiveness
4. Seal every gap, crack, and penetration in the separating elements; sound travels through the smallest openings
5. Pre-completion testing is required for conversions (Robust Details is not available for conversions)
6. Consider the impact of floor build-up height on headroom, door thresholds, and staircase landings
7. Sound insulation is easier to achieve in concrete-framed buildings than in timber-framed ones; assess the existing structure carefully