Section 5: Internal walls and floors for new buildings
Introduction
5.1 This Section gives examples of internal wall and floor constructions that meet the laboratory sound insulation values set out in Section 0: Performance - Table 2.
5.2 These constructions have been designed to give insulation against airborne sound. For internal floors, insulation against impact sound could be improved by adding a soft covering (e.g. carpet).
5.3 They are grouped in four main types as shown below.
5.4 Internal wall type A or B Timber or metal frame
The resistance to airborne sound depends on the mass per unit area of the leaves, the cavity width, frame material and the absorption in the cavity between the leaves.
5.5 Internal wall type C or D Concrete or aircrete block
The resistance to airborne sound depends mainly on the mass per unit area of the wall.
5.6 Internal floor type A or B Concrete planks or concrete beams with infilling blocks
The resistance to airborne sound depends on the mass per unit area of the concrete base or concrete beams and infilling blocks. A soft covering will reduce impact sound at source.
5.7 Internal floor type C Timber or metal joist
The resistance to airborne sound depends on the structural floor base, the ceiling and the absorbent material. A soft covering will reduce impact sound at source.
5.8 For both internal walls and internal floors the constructions are ranked, as far as possible, with constructions giving better sound insulation given first.
Doors
5.9 Lightweight doors with poor perimeter sealing provide a lower standard of sound insulation than walls. This will reduce the effective sound insulation of the internal wall. Ways of improving sound insulation include ensuring that there is good perimeter sealing or by using a doorset.
5.10 See Building Regulation Part F - Ventilation and Part J - Combustion appliances and fuel storage systems.
Layout
5.11 If the stair is not enclosed, then the potential sound insulation of the internal floor will not be achieved; nevertheless, the internal floor should still satisfy Requirement E2.
5.12 It is good practice to consider the layout of rooms at the design stage to avoid placing noise sensitive rooms next to rooms in which noise is generated. Guidance on layout is provided in BS 8233:1999 Sound Insulation and Noise Reduction for Buildings. Code of Practice.
Junction requirements for internal walls
5.13 Section 3: Separating Floors contains important guidance on junctions of separating floors with internal walls.
5.14 Fill all gaps around internal walls to avoid air paths between rooms.
Junction requirements for internal floors
5.15 Section 2: Separating Walls contains important guidance on junctions of separating walls with internal floors.
5.16 Fill all gaps around internal floors to avoid air paths between rooms.
5.17 Internal wall type A Timber or metal frames with plasterboard linings on each side of frame (see Diagram 5.1)
• each lining to be two or more layers of plasterboard, each sheet of minimum mass per unit area 10kg/m²;
• linings fixed to timber frame with a minimum distance between linings of 75mm, or metal frame with a minimum distance between linings of 45mm;
• all joints well sealed.
Diagram 5.1 Internal wall type A
5.18 Internal wall type B Timber or metal frames with plasterboard linings on each side of frame and absorbent material (see Diagram 5.2)
• single layer of plasterboard of minimum mass per unit area 10kg/m²;
• linings fixed to timber frame with a minimum distance between linings of 75mm, or metal frame with a minimum distance between linings of 45mm;
• an absorbent layer of unfaced mineral wool batts or quilt (minimum thickness 25mm, minimum density 10kg/m³) which may be wire reinforced, suspended in the cavity;
• all joints well sealed.
Diagram 5.2 Internal wall type B
5.19 Internal wall type C Concrete block wall, plaster or plasterboard finish on both sides (see Diagram 5.3)
• minimum mass per unit area, excluding finish 120kg/m²;
• all joints well sealed;
• plaster or plasterboard finish on both sides.
Diagram 5.3 Internal wall type C
5.20 Internal wall type D Aircrete block wall, plaster or plasterboard finish on both sides (see Diagram 5.4)
• for plaster finish, minimum mass per unit area, including finish 90kg/m²;
• for plasterboard finish, minimum mass per unit area, including finish 75kg/m²;
• all joints well sealed;
• internal wall type D should only be used with the separating walls described in this Approved Document where there is no minimum mass requirement on the internal masonry walls.
See guidance in Section 2;
• internal wall type D should not be used as a load-bearing wall connected to a separating floor, or be rigidly connected to the separating floors described in this Approved Document.
See guidance in Section 3.
Diagram 5.4 Internal wall type D
5.21 Internal floor type A Concrete planks (see Diagram 5.5)
• minimum mass per unit area 180kg/m²;
• regulating screed optional;
• ceiling finish optional.
Note Insulation against impact sounds can be improved by adding a soft covering (e.g. carpet).
Diagram 5.5 Internal floor type A
5.22 Internal floor type B Concrete beams with infilling blocks, bonded screed and ceiling (see Diagram 5.6)
• minimum mass per unit area of beams and blocks 220kg/m²;
• bonded screed required. Sand cement screeds should have a minimum thickness of 40mm. For proprietary bonded screed products, seek manufacturer's advice on the appropriate
thickness;
• ceiling finish required. Use ceiling treatment C or better from Section 3.
Note Insulation against impact sounds can be improved by adding a soft covering (e.g. carpet).
Diagram 5.6 Internal floor type B
5.23 Internal floor type C Timber or metal joist, with wood-based board and plasterboard ceiling, and absorbent material (see Diagram 5.7)
• floor surface of timber- or wood-based board, minimum mass per unit area 15kg/m²;
• ceiling treatment of single layer of plasterboard, minimum mass per unit area 10kg/m², fixed using any normal fixing method;
• an absorbent layer of mineral wool (minimum thickness 100mm, minimum density 10kg/m³) laid in the cavity.
Note:
Insulation against impact sounds can be improved by adding a soft covering (e.g. carpet).
Diagram 5.7 Internal floor type C
Note Electrical cables give off heat when in use and special precautions may be required when they are covered by thermally insulating materials. See BRE BR 262, Thermal Insulation: avoiding risks, Section 2.4.
