Table 2.1 Separating wall junctions reference table.

Separating wall type
Building element attached to separating wall Type 1 Type 2 Type 3 Type 4
External cavity wall with masonry inner leaf G G G N
External cavity wall with timber frame inner leaf G G G G
External solid masonry wall N N N N
Internal wall - framed G G G G
Internal wall - masonry G G X G
Internal floor - timber G G G G
Internal floor - concrete G G G N
Ground floor - timber G G G G
Ground floor - concrete G G G G
Ceiling and roof space G G G G
For flats the following may also apply:
Separating floor type 1 concrete base with ceiling and soft floor covering See Guidance in Section 3, Separating
Separating floor type 2 concrete base with ceiling and floating floor floors and associated flanking
Separating floor type 3 timber frame base with ceiling and platform floor constructions for new buildings

Key: G = guidance available; N = no guidance available (seek specialist advice); X = do not build

Note: Where any building element functions as a separating element (e.g. a ground floor that is also a separating floor for a basement flat) then the separating element requirements should take precedence.

2.10 Table 2.1 indicates the inclusion of guidance in this document on the junctions that may occur between each of the four separating wall types and various attached building elements.

Mass per unit area of walls

2.11 The mass per unit area of a wall is expressed in kilograms per square metre (kg/m2). The method for calculating mass per unit area is shown in Annex A.

2.12 The density of the materials used (and on which the mass per unit area of the wall depends) is expressed in kilograms per cubic metre (kg /m3). When calculating the mass per unit area for bricks and blocks use the density at the appropriate moisture content from Table 3.2, CIBSE Guide A (1999).

2.13 The guidance describes constructions that use blocks without voids. For blocks with voids, seek advice from the manufacturer.

Plasterboard linings on separating and external masonry walls

2.14 The guidance describes some constructions with only wet finishes. For dry finishes, seek advice from the manufacturer.

2.15 Wherever plasterboard is recommended, or the finish is not specified, a drylining laminate of plasterboard with mineral wool may be used. For other drylining laminates, seek advice from the manufacturer.

2.16 Plasterboard linings should be fixed according to manufacturers instructions.

Cavity widths in separating cavity masonry walls

2.17 Recommended cavity widths are minimum values.

Wall ties in separating and external cavity masonry walls

2.18 Suitable wall ties for use in masonry cavity walls are indicated in the guidance by reference to either tie type A or B.

2.19 Tie type A Connect the leaves of a cavity masonry wall only where necessary by butterfly ties as described in BS 1243:1978 Metal ties for cavity wall construction, and spaced as required for structural purposes (BS 5628-3:2001 Code of practice for use of masonry. Materials and components, design and workmanship, which limits this tie type and spacing to cavity widths of 50 mm to 75 mm with a minimum masonry leaf thickness of 90 mm). Alternatively, use wall ties with an appropriate measured dynamic stiffness for the cavity width. The specification for wall ties of dynamic stiffness, kXmm in MN/m with a cavity width of X mm and n ties/m2 is n.kXmm<4.8 MN/m3.

2.20 Tie type B (for use only in external masonry cavity walls where tie type A does not satisfy the requirements of Building Regulation Part A - Structure)

Resistance to the passage of sound 17

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