SCOTTISH EXECUTIVE

Building Regulations: Technical Standards

Provisions deemed to satisfy the standards

AIRBORNE SOUND AND IMPACT SOUND

(H2.1, The requirements of H2.1 for airborne sound and H2.2 and H2.3 for impact sound will be met where

H2.2, walls, floors and roofs -

H2.3)

a. are constructed in accordance with the specified constructions given in points 1 to 17; or

b. achieve the standards given in point 18 when tested in accordance with points 19 to 29.

Specified constructions

1 The requirements for sound insulation will be met where walls and floors are constructed as specified below (but note that the diagrams do not show all the structural bracing that may be required).

2 The thicknesses, masses, and other dimensions specified are the minimum required unless otherwise stated; greater figures are therefore permissible. Timber sizes quoted are the minimum actual sizes required.

3 Where a mass is specified for a wall it is expressed in kg/m² of wall face area. For a floor the mass is expressed in kg/m² on plan.

4 To calculate the mass of a leaf of masonry the formulae in point 5 must be used. Densities of bricks or blocks (at 3% moisture content) may be taken from a current BBA Certificate or from the manufacturer's literature, in which case the local authority may ask for confirmation e.g. that the measurement was done by an accredited test house. Note that the quoted density of bricks or blocks is normally the apparent density, i.e. the weight divided by the volume including perforations, voids or frogs. This is the density appropriate to the formulae. For co-ordinating course heights other than those given in point 5 use the formula for the nearest height. Include any finish of plaster, render or dry lining in calculating the mass unless otherwise stated.

5 To calculate the mass of a masonry leaf use the following formulae.

Co-ordinating height of masonry course (mm)	Formulae to be used
75	formula
100	formula
150	formula
200	formula

Where	M = Mass of 1m² of leaf in kg/m²
	T = Thickness of masonry in metres i.e unplastered thickness)
	D = Density of masonry units in kg/m³ (at 3 % moisture content)
	N = Number of finished faces
	P = Mass of 1m² of wall finish in kg/m² (see below)
Mass of plaster (assumed thickness 13 mm)
	Cement Render = 29 kg/m²
	Gypsum = 17 kg/m²
	Lightweight = 10 kg/m²
	Plasterboard = 10 kg/m²

6 In point 5 a mortar joint of 10 mm and a dry, set mortar density of 1800 kg/m³ are assumed. Values within 10% of these figures are acceptable.

7 For in-situ concrete or screeds calculate the mass by multiplying the density (kg/m³) by the thickness (in metres). For slabs or composite floor bases divide the total mass of the element (kg) by the plan area of the element (m²).

Conditions on the use of specified constructions

8 In any separating wall being built to meet the specified construction standard, the following conditions must be met -

a. no opening is permitted except a doorway between a dwelling and a stairway or passage where the doorway is protected by a fire door satisfying Part D;

b. no service pipes or ducts may pass through except between a dwelling and a stairway, passage or duct where the pipes and ducts are protected to satisfy Part D;

c. chases for services are allowed in wall type 1 or 2 provided the depth of any horizontal chase does not exceed one-sixth of the thickness of the leaf, and the depth of any vertical chase does not exceed one-third of the thickness; chases back to back in a single leaf are not permitted; in wall type 3 services may pierce the free-standing panels provided any gaps are sealed with tape or caulking; no services are permitted in wall type 4; and

d. flues are only permitted in walls where the flues are of masonry construction (including precast concrete flue blocks); no flues are permitted in wall type 4.

9 In any separating floor being built to meet the specified construction standard no openings are permitted except openings for service ducts, pipes or flues protected to satisfy Part D or Part F and which are also enclosed above and below the floor to satisfy this Part.

10 Wall type 1: solid masonry

The resistance to airborne sound depends mainly on the mass of the wall.

Points to watch

Fill masonry joints with mortar (to achieve the mass and avoid air paths).

Limit the pathways around the wall (to reduce flanking transmission).

Construction

Five wall constructions which give suitable resistance to direct transmission are specified. Details of how junctions must be made to limit flanking transmission follow.

A. Brick, plastered both sides.

Mass including plaster 375 kg/m².

13 mm plaster each side.

Lay bricks in a bond which includes headers.

Example: 215 mm brick, lightweight plaster, 75 mm coursing; brick density of 1610 kg/ m³ gives the required mass.

B. Concrete block, plastered both sides. Mass including plaster 415 kg/m².

13 mm plaster each side.

Use blocks which extend to the full thickness of the wall.

Example: 215 mm block, lightweight plaster, 110 mm coursing; block density of 1840 kg/m³ gives the required mass.

C. Brick, plasterboard both sides.

Mass including plasterboard 375 kg/m².

12.5 mm plasterboard each side, use any normal fixing method.

Lay bricks in a bond which includes headers.

Example: 215 mm brick, 75 mm coursing; brick density of 1610 kg/m³ gives the required mass.

D. Concrete block, plasterboard both sides.

Mass of masonry alone 415 kg/m².

12.5 mm plasterboard each side, use any normal fixing method.

Use blocks which extend to the full thickness of the wall.

Example: 215 mm block, 150 mm coursing; block density of 1840 kg/m³ gives the required mass.

E. Concrete (minimum density 1500 kg/m³), in-situ or large panel.

Plaster optional.

Mass (including plaster if used) 415 kg/m².

Fill joints between panels with mortar.

Example: an unplastered wall of density 2200 kg/m³; 190mm thickness gives the required mass.

diagram

10. Junctions for wall type 1

Roof

Fire-stop the joint between wall and roof (see
Part D).

Ceiling and roof space

Where there is a heavy ceiling with sealed joints (12.5 mm plasterboard or equivalent), the mass of the wall above the ceiling may be reduced to 150 kg/m². If lightweight aggregate blocks are used to reduce mass, seal one side with cement paint or plaster skim.

Intermediate and ground floors

With a timber floor do not build joists into the wall, use hangers. With a concrete floor either the wall or the floor may be carried through.

External wall

The outer leaf of a cavity wall may be of any construction. Where a cavity wall has an inner leaf of masonry; or where the external wall is of solid masonry -

a.

i. the masonry of the walls must be bonded together, or

ii. the masonry of the external wall must abut the separating wall and be tied to it with ties at no more than 300 mm centres vertically,

to create a homogeneous unit; and

b. the masonry must have a mass of 120 kg/m² unless the length of the external wall is limited by openings,

i. of 1 metre high,

ii. on both sides of the separating wall at every storey, and

iii. not more than 700 mm from the face of the separating wall on both sides¹.

Where a cavity wall has an inner leaf of timber construction it must -

c. abut the separating wall;

d. be tied to it with ties at no more than 300 mm centres vertically; and

e. have the joints sealed with tape or caulking .

f. a short length of wall will not vibrate excessively at low frequencies to give flanking transmissions.

Partitions

There are no restrictions on a partition wall meeting a type 1 separating wall.

diagram

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