Internal walls

6.3

Also See:

2.1

6.3.5Load-bearing timber walls

Internal load-bearing timber walls shall be designed to support and transfer loads to foundations safely and without undue movement. Issues to be taken into account include:

structural elements
timber separating walls
timber quality.

Structural elements

Structural design of load-bearing timber walls should be in accordance with BS EN 1995-1-1.

When constructing structural elements:

individual studs, sills and headplates should be 38mm x 75mm minimum, although larger sizes may be required to achieve an adequate level of fire resistance

studs should be spaced at a maximum of 600mm centres

lintel and cripple studs should be provided to each opening, except when the stud spacing is unaffected

multiple joists should be supported by multiple studs

framing joints should be secured with a minimum of two nails per joint

where internal walls are made up from panels, structural continuity should be maintained, e.g. by the use of a continuous top binder.

Timber separating walls

The type and spacing of wall ties and straps should limit sound transmission across the cavity in accordance with building regulations.

Wall ties should:

be specified in accordance with the system designer’s recommendations

have a maximum cross-section of 40mm x 3mm

be fixed below ceiling level

be spaced a minimum of 1.2m horizontally.

Timber quality

Timber should be of the appropriate grade, moisture content and size to support the imposed loads.

Structural timber should be of a suitable grade and specified according to the strength classes in BS EN 338, e.g. C16 or C24. When graded to BS 4978:

the species should be included in accordance with BS EN 1912 or the class strength specified

BS EN 338 can be used to determine strength class.

Timber should have a maximum moisture content of 20%.

Structural softwood for internal use should be:

dry graded to BS 4978

marked ‘DRY’ or ‘KD’.

Timber for walls which are to be dry-lined should be regularised and comply with BS 8212. Finger joints should comply with BS EN 15497.