Make sure you know what performance standards in Part E are required for each room of the building at an early design stage. If the function of a building or room changes during the build programme, altering the design details to meet tougher acoustic performance requirements could be costly and may spoil the appearance of the interior.
2. Junction details
Care should be taken to detail junctions correctly between the separating walls and other elements such as floors, roofs, external walls and internal walls. The approved document contains notes and diagrams on separating wall types but is by no means exhaustive. For example, it does not offer any guidance on using plasterboard linings on separating and external masonry walls. Where there is no guidance or construction details, contact the manufacturer.
Ensure doors used between corridors and rooms in flats have a good perimeter sealing and a minimum mass per unit area of 25 kg/m2 or a minimum sound reduction index of 29 dB Rw (measured according to BS EN ISO 1403:1995 and rated according to BS EN ISO 717-1:1997).
The approved document includes the following advice for solid masonry constructions:
- Use bricks/blocks that extend to full thickness of wall
- Ensure that an external cavity wall is stopped by a flexible closer at the junction with a separating wall, unless the cavity is fully filled with mineral wool or other suitable material
- Stagger positions of sockets on opposing sides
- Ensure that flue blocks do not adversely affect the sound insulation and that a suitable finish is used over the flue blocks (see BS 1289-:1986 and seek advice)
- Fill and seal all masonry joints with mortar.
For cavity masonry:
- As above but keep the cavity leaves separate below ground floor.
And for masonry between independent panels:
- As above but fix the panels or the supporting frames to the ceiling and floor only, not the masonry core. Also ensure all joints are taped and sealed.
5. Framed walls with absorbent material
The approved document only offers advice on timber-framed walls. For steel, seek advice from manufacturer or consult forthcoming guides from the Steel Construction Institute.
- Where fire stops are needed in the cavity between frames make sure they are either flexible or fixed to only one frame
- Ensure that each layer of plasterboard is independently fixed to the stud frame.
6. Concrete base with ceiling and floating floor
- Fill all joints in floor to avoid air paths
- Give special attention to the perimeter detailing and pipe penetrations
- Build a separate concrete floor into walls around its perimeter where walls are masonry
- Fill with mortar any gap that may form between the head of the masonry wall and the underside of the concrete floor.
With ceiling and soft floor covering:
- As above but also fix or glue soft floor covering to the floor to reduce impact sound. Covering should be at least 4.5 mm thick or reduce impact sound by 17 dB.
7. Floating floors (floating layers and resilient layers)
- Leave a small gap between the floating layer and wall at all room edges and fill with flexible sealant
- Leave a small gap (about 5 mm) between the skirting and floating layer and fill with flexible sealant
- Lay resilient materials in rolls or sheets with lapped joints or with joints tightly butted and taped
- Use paper facing on the upper side of fibrous materials to prevent screed entering the resilient layer.
8. Timber frame base with ceiling and platform floor
- Use the correct density of resilient layer and ensure it can carry the anticipated load
- Use an expanded or extruded polystyrene strip (or similar resilient material) around the perimeter, which is about 4 mm higher than the upper surface of the floating layer to ensure that a gap is maintained between the wall and floating layer during construction. The gap should be filled with a flexible sealant later
- Lay resilient materials in sheets with joints tightly butted and taped.
9. Absorption material
There is a requirement to provide extra absorption material in corridors, hallways, stairways and entrance halls to reduce reverberation in the common internal parts of residential buildings. Seek specialist advice at an early stage to determine how much absorption is required and to minimise the impact on the design. Section 7 of the Approved Document outlines two methods of satisfying this requirement.
10. Pre-completion testing
Make sure that enough time is built into the build programme for pre-completion testing. If the tests are carried out close to handover and there is a failure, remedial work may cause delays, and even litigation. Testing should be carried out by an approved testing house. Currently these are UKAS approved but Building Control is considering accepting an accreditation scheme put together by the Association of Noise Consultants for its members.