Internal Partitions - Timber Stud

A stud partition generally consists of plasterboard nailed to both sides of a timber framework. The plasterboard used for this type of partition typically has a tapered edge which allows for flush jointing.

The timber framing must be constructed accurately, the spacing and alignment of timber is important for nailing of plasterboard. It is important to ensure that the timber used is dried correctly with a moisture content of less than 20%, this will help prevent distortion or warping which may lead to cracking of joints.

In situations where the internal partitions, of timber stud, are to be load bearing the timber to be used must achieve a strength class of C14 or more. The studs should be fixed at 400m centres and should be a minimum of 44mm x 100mm. Load bearing studs should be installed with a double header, sole pieces and two rows of noggings.

When carrying floors, load bearing partitions may require fire resistance, additional guidance on this can be obtained from approved documents which is available in Appendix H of this app.

It is recommended that two rows of noggings are provided for timber stud partitions which contain studs having a cross-section of 75 x 36 mm or less having a height of 2438mm. A single nogging is usually sufficient in instances where a larger stud is used.

All board edges in fire rated partitions, in which vapour check plasterboard is used, require noggings.

It is important to follow the manufacturer’s recommendations when using any proprietary metal stud partitioning systems.

Diagram C141 -Typical non-loadbearing stud partition - timber

The recommended maximum spacings of studs for different plasterboard thicknesses and widths are detailed in the table below.

Table C19 - Recommended stud spacing for different plasterboard thickness and spans

Plasterboard fixing

The most commonly used sizes of plasterboard used in domestic construction have a sheet size of 2438mm x 1200mm with a thickness of either 12.5mm or 9.5mm.

Each sheet has a front and a back, the front is the face on which the paper covers over the edges and is known as the ivory face (or the coloured face where moisture board, fireline board or similar are used). The back has a double thickness paper and is known as the grey face.

While each manufacturer will have their own specific recommendations and requirements when it comes to Gypsum plasterboard the boards should be fixed using steel nails that have been zinc electroplated, hot dip galvanised or sheradized. These steel nails should have a shank having a minimum finished diameter of 2.5mm and a head having a minimum diameter 7mm.

Boards should be nailed to every support from the centre of the board outwards at approximately 150mm centres. Ensure all nails are driven home without the head of the nail piercing the surface of the slab while leaving a shallow compression to aid the spotting process. In partitions that are not required to be fire rated and will not be load bearing boards should be placed with the long edge parallel to the studs so that the bound edges are joined on the stud.

Zinc electroplated or block phosphate oiled steel self drilling and tapping drywall screws should be used with trumpet countersunk or cross punched heads should be provided at 230mm centres. The table opposite illustrates the minimum lengths for screws and nails.

Table C20 - Minimum required nail and screw lengths

Screws should be a minimum 10mm longer than the total laminate thickness when fixing thermal laminate boards to metal studs and a minimum of 25mm longer when fixing the boards to timber studs.

Diagram C142 - Typical plasterboard joint details

Fixing Details

Buttressing

It is possible to use stud partitions to provide internal buttressing to external walls in upper floors only when :

  • The partition is greater than 1200mm in length.

  • 75mm x 35mm minimum kiln dried studs at a maximum of 400mm centres are used.

  • Two rows of noggings are used.

  • When fixing to the external wall, the end stud should be drilled screw fixed to the wall at the top and at each of the noggings.

Diagram C143 - Typical fixing detail for internal buttressing to external walls by stud partitions in upper floors

Sound insulation To ensure the best possible level of sound insulation between spaces is achieved i.e. between WC’s and other spaces, a sound insulation quilt material should be provided between studs with a 12.5mm plasterboard fixed to the studs. Alternative details may be obtained from the manufacturer with respect to the individual site specific requirements.

Use of ceramic wall tiling in areas that are persistently wet

In areas where there is regularly significant levels of moisture i.e. bathrooms, shower rooms it is important to ensure that a moisture resistant plasterboard is used. Wall tiles may be fixed directly to the moisture board however the manufacturers guidelines must be adhered to

Alternatives to moisture resistant plasterboard may be used including moisture resistant plywood and proprietary moisture resistant building boards.

The following lists guidelines which should be followed to ensure that water penetration does not occur around baths and shower trays:

  • Ensure the tiles, adhesive and grout being used are correct for the location and background they are being placed by checking with the tile manufacturer.

  • All products should be used strictly in accordance with the manufacturers specifications.

  • Perimeter movement may be an issue for baths and shower trays installed on timber floors due to deflection of joists and shrinkage due to drying. To overcome this problem, install fittings near joist supports.

  • Fittings as shown below which incorporate an integral upstand should be used. Proprietary tile trims/beads can be used at the junction between walls and fittings as an alternative.

For joints between walls and fittings, silicon based sealants should be used.

Diagram C144 - Typical detail for tiling at the junction of a wall and sanitary fittings

Construction of stud partitions

To avoid the risk of ceiling cracking or deflection build non-loadbearing stud partitions off double joists. As an alternative to the above an extra joist may be placed directly under the line of the partition.

**Please Note:* A specially designed RSJ or universal beam may be required to support load bearing partitions.*

PARTITIONS SHOULD BE PROPERLY SECURED IN PLACE BEFORE ROOF LOAD IS APPLIED.

Drilling and notching studs

Notching of studs should not normally happen, instead services should run through drilled holes in the centreline of the stud. The service holes should be less than ¼ the width of the stud and acceptable location zones are illustrated opposite.

Diagram C145 -Typical stud partition built on timber floor - non load bearing

Diagram C146 - Typical locations of drill holes in studs

Stud partition construction

When stud walls run at right angles to joists, point loads are exerted on the joists which need to be taken into account when designing the joists. A double sole piece, as detailed below should be incorporated under the partition in this case also.

Diagram C147 - Typical sole piece location for stud partition built at right angles to the joist

When partitions run at right angles to joists, the partition heads should be fixed to the ceiling joists. Where partitions are running parallel to joists, fix the partitions to noggings placed between the joists. Noggings should be provided at 400mm centres.

To accommodate fixing of sanitary fittings, radiators, etc. provide noggings between studs.

Diagram C148 - Typical nogging detail at the head of partitions

**Please Note:* The details provided above are stud partitions under a cut timber roof construction where the ceiling material is fixed after the partition is constructed. The ceiling material is often fixed before the partition is constructed where prefabricated trussed roof construction is used.*