Specification 28 Sound insulation for building elements

This Specification lists the weighted sound reduction index R_W for some common forms of construction.

Wall systems listed in S28C4 to S28C7 having a minimum 20 mm cavity between 2 separate leaves are deemed to be discontinuous construction if—

1. for masonry, where wall ties are required to connect leaves, the ties are of the resilient type; and
2. for other than masonry, there is no mechanical linkage between leaves except at the periphery.

(1) The forms of wall construction described in S28C4 to S28C7 and floor construction described in S28C8 to S28C10, are considered to have the R_w, R_w + C_tr and L_n,w stated in those clauses.

(2) The forms of construction referred to in (1) must be installed as follows:

1. Masonry units must be laid with all joints filled solid, including those between the masonry and any adjoining construction.
2. Joints between concrete slabs or panels and any adjoining construction must be filled solid.
3. For sheeting materials—
   1. if one layer is required on both sides of a wall, it must be fastened to the studs with joints staggered on opposite sides; and
   2. if two layers are required, the second layer must be fastened over the first layer so that the joints do not coincide with those of the first layer; and
   3. joints between sheets or between sheets and any adjoining construction must be taped and filled solid.
4. Timber or steel-framed construction — perimeter framing members must be securely fixed to the adjoining structure and—
   1. bedded in resilient compound; or
   2. the joints must be caulked so that there are no voids between the framing members and the adjoining structure.
5. Services must not be chased into concrete or masonry elements.
6. A door or panel required to have a certain R_w + C_tr that provides access to a duct, pipe or other service must—
   1. not open into any habitable room (other than a kitchen); and
   2. be firmly fixed so as to overlap the frame or rebate of the frame by not less than 10 mm, be fitted with a sealing gasket along all edges and be constructed of—
      1. wood, particleboard or blockboard not less than 33 mm thick; or
      2. compressed fibre-reinforced cement sheeting not less than 9 mm thick; or
      3. other suitable material with a mass per unit area not less than 24.4 kg/m².
7. A water supply pipe must—
   1. only be installed in the cavity of discontinuous construction; and
   2. in the case of a pipe that serves only one sole-occupancy unit, not be fixed to the wall leaf on the side adjoining any other sole-occupancy unit and have a clearance not less than 10 mm to the other wall leaf.
8. Electrical outlets must be offset from each other—
   1. in masonry walling, not less than 100 mm; and
   2. in timber or steel-framed walling, not less than 300 mm.

(1) Acceptable forms of construction for masonry walls are set out in (2) to (9).

(2) Two leaves of 110 mm clay brick masonry with—

1. a cavity of not less than 50 mm between leaves; and
2. 50 mm thick glass wool insulation with a density of 11 kg/m³ or 50 mm thick polyester insulation with a density of 20 kg/m³ in the cavity,

has an R_w + C_tr of not less than 50 and an R_w of not less than 50, if constructed as shown in Figure S28C4a.

(3) Two leaves of 110 mm clay brick masonry with—

1. a cavity of not less than 50 mm between leaves; and
2. 13 mm cement render on each outside face,

has an R_w + C_tr of not less than 50 and an R_w of not less than 50, when constructed as shown in Figure S28C4b.

(4) A single leaf of 110 mm clay brick masonry with—

1. a row of 70 mm x 35 mm timber studs or 64 mm steel studs at 600 mm centres, spaced 20 mm from the masonry wall; and
2. 50 mm thick glass or mineral wool insulation with a density of 11 kg/m³ positioned between studs; and
3. one layer of 13 mm plasterboard fixed to outside face of studs and outside face of masonry,

has an R_w + C_tr of not less than 50 and an R_w of not less than 50, if constructed as shown in Figure S28C4c.

(5) A single leaf of 90 mm clay brick masonry with—

1. a row of 70 mm x 35 mm timber studs or 64 mm steels studs at 600 mm centres, spaced 20 mm from each face of the masonry wall; and
2. 50 mm thick glass or mineral wool insulation with a density of 11 kg/m³ positioned between studs in each row; and
3. one layer of 13 mm plasterboard fixed to studs on each outside face,

has an R_w + C_tr of not less than 50 and an R_w of not less than 50, if constructed as shown in Figure S28C4d.

(6) A single leaf of 150 mm brick masonry with 13 mm cement render on each face has an R_w of not less than 50 if constructed as shown in Figure S28C4e.

(7) A single leaf of 220 mm brick masonry with 13 mm cement render on each face has an R_w + C_tr of not less than 50 and an R_w of not less than 50, if constructed as shown in Figure S28C4f.

(8) 110 mm thick brick masonry with 13 mm cement render on each face has an R_w of not less than 45 if constructed as shown in Figure S28C4g.

(9) 110 mm thick concrete brickwork has an R_w of not less than 45 if constructed as shown in Figure S28C4h.

(1) Acceptable forms of construction for concrete walls are set out in (3) to (12).

(2) For the purposes of this clause, the term ‘concrete panel’ is a reference to a solid in-situ concrete panel or solid pre-cast concrete panel.

(3) A 150 mm thick concrete panel has an R_w + C_tr of not less than 50 and an R_w of not less than 50, if constructed as shown in Figure S28C5a.

(4) A 150 mm thick concrete panel with one layer of 10 mm plasterboard fixed to 28 mm metal furring channels on each face, has an R_w of not less than 50, if constructed as shown in Figure S28C5b.

(5) A 200 mm thick concrete panel with one layer of 13 mm plasterboard or 13 mm cement render on each face has an R_w + C_tr of not less than 50 and an R_w of not less than 50, if constructed as shown in Figure S28C5c.

(6) A 100 mm thick concrete panel with—

1. a row of 64 mm steel studs at 600 mm centres, spaced 25 mm from the concrete panel; and
2. 80 mm thick polyester insulation or 50 mm thick glass wool insulation with a density of 11 kg/m³, positioned between studs; and
3. two layers of 13 mm plasterboard fixed to outside face of studs and one layer of 13 mm plasterboard fixed to outside face of concrete panel,

has an with an R_w + C_tr of not less than 50 and an R_w of not less than 50, if constructed in accordance with Figure S28C5d.

(7) A 125 mm thick concrete panel with—

1. a row of 64 mm steel studs at 600 mm centres, spaced 20 mm from the concrete panel; and
2. 70 mm polyester insulation with a density of 9 kg/m³, positioned between studs; and
3. one layer of 13 mm plasterboard fixed to the outside face of the studs,

has an with an R_w + C_tr of not less than 50 and an R_w of not less than 50, if constructed in accordance with Figure S28C5e.

(8) A 125 mm thick concrete panel has an R_w of not less than 50, if constructed as shown in Figure S28C5f.

(9) A 100 mm concrete panel with 13 mm cement render or one layer of 13 mm plasterboard on each face has an R_w of not less than 50, if constructed as shown in Figure S28C5g.

(10) A 190 mm thick concrete blockwork has an R_w of not less than 45, if constructed as shown in Figure S28C5h.

(11) 140 mm thick concrete blockwork, the face shell thickness of the blocks being not less than 44 mm and with—

1. 50 mm x 50 mm timber battens spaced at not more than 610 mm centres screw-fixed on one face of the blocks into resilient plugs with rubber inserts between battens and the wall; and
2. the face of the battens clad with 13 mm plasterboard,

has an R_w of not less than 45, if constructed as shown in Figure S28C5i.

(12) A concrete panel, 100 mm thick, has an R_w of not less than 45, if constructed as shown in Figure S28C5j.

(1) Acceptable forms of construction for autoclaved aerated concrete walls are set out in (2) to (5).

(2) A 75 mm thick autoclaved aerated concrete wall panel with—

1. a row of 64 mm steel studs at 600 mm centres, spaced 20 mm from the autoclaved aerated concrete wall panel; and
2. 75 mm thick glass wool insulation with a density of 11 kg/m³ positioned between studs; and
3. one layer of 10 mm moisture resistant plasterboard or 13 mm fire protective grade plasterboard fixed to outside face of studs and outside face of autoclaved aerated concrete wall panel,

has an R_w + C_tr of not less than 50 and an R_w of not less than 50, if constructed as shown in Figure S28C6a.

(3) A 75 mm thick autoclaved aerated concrete wall panel with—

1. a row of 64 mm steel studs at 600 mm centres, spaced 35 mm from the autoclaved aerated concrete panel wall; and
2. 28 mm metal furring channels fixed to the outside face of the autoclaved aerated concrete wall panel, with 50 mm thick polyester insulation with a density of 9 kg/m³ positioned between furring channels and one layer of 13 mm fire protective grade plasterboard fixed to furring channels; and
3. 105 mm thick glass wool insulation with a density of 7 kg/m³ positioned between studs; and
4. one layer of 13 mm fire protective grade plasterboard fixed to the outside face of the studs,

has an R_w + C_tr of not less than 50 and an R_w of not less than 50, if constructed as shown in Figure S28C6b.

(4) Two leaves of 75 mm autoclaved aerated concrete wall panel with—

1. a cavity not less than 30 mm between panels containing 50 mm glass wool insulation with a density of 11 kg/m³; and
2. one layer of 10 mm plasterboard fixed to outside face of each panel,

has an R_w + C_tr of not less than 50 and an R_w of not less than 50, if constructed as shown in Figure S28C6c.

(5) A 75 mm thick autoclaved aerated concrete wall panel with—

1. one layer of 10 mm moisture resistant plasterboard on one face; and
2. 28 mm metal furring channels and resilient mounts, 75 mm polyester insulation with a density of 9 kg/m³ and 13 mm fire-protective grade plasterboard fixed to the other face,

has an R_w of not less than 50, if constructed as shown in Figure S28C6d.

(1) Acceptable forms of construction for timber and steel framing walls are set out in (2) to (11).

(2) Two rows of 70 x 35 mm timber studs at 450 mm centres with—

1. an air gap not less than 20 mm between the rows of studs; and
2. 75 mm thick glass or mineral wool insulation with a density of 8 kg/m³ or 60 mm thick polyester insulation with a density of 11 kg/m³ positioned between one row of studs; and
3. two layers of 13 mm fire-protective grade plasterboard or one layer of 6 mm fibre-cement sheet and one layer of 13 mm fire-protective grade plasterboard, fixed to outside face of studs,

has an R_w + C_tr of not less than 50 and an R_w of not less than 50, if constructed as shown in Figure S28C7a.

(3) One row of 70 mm x 35 mm staggered timber studs, without noggings between adjacent studs, at not less than 450 mm centres, fixed to 90 mm x 35 mm wall plates with—

1. 75 mm thick glass or mineral wool insulation with a minimum density of 8 kg/m³ positioned between studs; and
2. two layers of 13 mm fire-protective grade plasterboard fixed to outside face of studs,

has an R_w of not less than 50, if constructed as shown in Figure S28C7b.

(4) One row of 70 mm x 35 mm timber studs at not less than 600 mm centres with—

1. 75 mm thick glass or mineral wool insulation with a minimum density of 8 kg/m³ positioned between studs; and
2. two layers of 13 mm fire-protective grade plasterboard fixed to outside face of studs,

has an R_w of not less than 45, if constructed as shown in Figure S28C7c.

(5) One row of 70 mm x 35 mm timber studs at not less than 450 mm centres with—

1. 28 mm furring channels installed horizontally on one side; and
2. two layers of 13 mm fire-protective plasterboard fixed on each face,

has an R_w of not less than 45, if constructed as shown in Figure S28C7d.

(6) Two rows of 64 mm steel studs at 600 mm centres with—

1. an air gap not less than 20 mm between the rows of studs; and
2. 50 mm thick glass wool insulation or 60 mm thick polyester insulation with a density of 11 kg/m³ positioned between one row of studs; and
3. two layers of 13 mm fire-protective grade plasterboard or one layer of 6 mm fibre-cement sheet and one layer of 13 mm fire-protective grade plasterboard, fixed to outside face of studs,

has an R_w + C_tr of not less than 50 and an R_w of not less than 50, if constructed as shown in Figure S28C7e.

(7) Two rows of 64 mm steel studs at 600 mm centres with—

1. an air gap not less than 80 mm between the rows of studs; and
2. 200 mm thick polyester insulation with a density of 14 kg/m³ positioned between studs; and
3. one layer of 13 mm fire-protective grade plasterboard and one layer 13 mm plasterboard on one outside face and one layer of 13 mm fire-protective grade plasterboard on the other outside face,

has an R_w + C_tr of not less than 50 and an R_w of not less than 50, if constructed as shown in Figure S28C7f.

(8) One row of 92 mm steel studs at 600 mm centres with—

1. 50 mm thick glass wool insulation with a density of 11 kg/m³ or 60 mm thick polyester insulation with a density of 8 kg/m³, positioned between studs; and
2. two layers of 13 mm fire-protective grade plasterboard or one layer of 6 mm fibre-cement sheet and one layer of 13 mm fire-protective grade plasterboard, fixed to each face,

has an R_w of not less than 50, if constructed as shown in Figure S28C7g.

(9) One row of 64 mm steel studs with 2 layers of 16 mm fire-protective grade plasterboard fixed to each face has an R_w of not less than 45, if constructed as shown in Figure S28C7h.

(10) One row of 64 mm steel studs with—

1. one layer of 16 mm fire-protective grade plasterboard fixed to one face; and
2. 50 mm thick glass or mineral wool insulation with a density of 11 kg/m³ positioned between the studs; and
3. two layers of fire-protective grade plasterboard fixed to the other face, the inner layer being 16 mm thick and the outer layer being 13 mm,

has an R_w of not less than 45, if constructed as shown in Figure S28C7i.

(11) One row of 64 mm steel studs with two layers of 13 mm plasterboard on each face has an R_w of not less than 45, if constructed as shown in Figure S28C7j.

(1) Acceptable forms of construction for concrete floors are set out in (2) to (4).

(2) 150 mm thick concrete slab with—

1. 28 mm metal furring channels and isolation mounts fixed to underside of slab, at 600 mm centres; and
2. 65 mm thick polyester insulation with a density of 8 kg/m³, positioned between furring channels; and
3. one layer of 13 mm plasterboard fixed to furring channels,

has an R_w + C_tr of not less than 50, an L_n,w of not more than 62 and an R_w of not less than 50, if constructed as shown in Figure S28C8a.

(3) 200 mm thick concrete slab with carpet on underlay has an R_w + C_tr of not less than 50, an L_n,w of not more than 62 and an R_w of not less than 50, if constructed as shown in Figure S28C8b.

(4) 100 mm thick concrete slab has an R_w + C_tr of not less than 45 and an R_w of not less than 45, if constructed as shown in Figure S28C8c.

(1) An acceptable form of construction for autoclaved aerated concrete floors is set out in (2).

(2) 75 mm thick autoclaved aerated concrete floor panel with—

1. 8 mm ceramic tiles with flexible adhesive and waterproof membrane, located above the slab; and
2. timber joists at 600 mm centres; and
3. R1.5 glass wool insulation positioned between timber joists; and
4. 28 mm metal furring channels and resilient mounts fixed to underside of joists; and
5. two layers of 13 mm plasterboard fixed to furring channels,

has an R_w + C_tr of not less than 50, an L_n,w of not more than 62 and an R_w of not less than 50, if constructed as shown in Figure S28C9.

(1) Acceptable forms of construction for timber floors are set out in (2) and (3).

(2) 19 mm thick particleboard floor sheeting with—

1. 190 mm x 45 mm timber joists at 450 mm centres; and
2. R2.5 glass or mineral wool insulation positioned between timber joists; and
3. 28 mm metal furring channels and isolation mounts fixed to underside of joists, isolation mounts to be of natural rubber with a dynamic factor of not more than 1.1 and static deflection of not less than 3 mm at actual operating load; and
4. two layers of 16 mm fire-protective grade plasterboard fixed to furring channels,

has an R_w + C_tr of not less than 50, an L_n,w of not more than 62 and an R_w of not less than 50, if constructed as shown in Figure S28C10a.

(3) Timber flooring with minimum 8.5 kg/m² mass, over 19 mm thick particleboard floor sheeting with—

1. 190 mm x 45 mm timber joists at not less than 450 mm centres; and
2. R2.5 glass or mineral wool insulation positioned between timber joists; and
3. 28 mm metal furring channels fixed to underside of joists at 600 mm centres by clip or mount; and
4. one layer of 13 mm acoustic grade plasterboard fixed to furring channels,

has an R_w + C of not less than 45 and an R_w of not less than 45, if constructed as shown in Figure S28C10b.