Timber Frame Information:

Timber framed construction method.

1. The method of construction generally used in the UK is known as platform frame. The vast majority (approximately 95%) of the timber frame buildings being built in the UK follow a relatively simple tried and trusted pattern. ‘Open panels’ (studs, rails, lintels, sheathing and breather membrane), that have been manufactured in a factory environment are delivered to site and craned onto a ‘platform’, which is formed by the building foundations and sole plate. The panels are fixed into position with nails and then floors - either as cassettes or loose joists (now frequently engineered joists), with a wood-based panel structural deck - are installed to create another platform. Another set of panels is positioned and fixed on top of the first floor plat-form and the process can be repeated to create a building of the required design height. The final part of the erection process is to position, fix and brace the roof, normally trussed rafters. ‘Open panel’ structures, such as this, are then dry-lined after the installation of services, insulation and a vapour control layer on site.
   
2. Higher levels of prefabrication can be achieved with ‘closed panels’ where the insulation, services, vapour control layer, internal linings, and possibly also the joinery and cladding are all applied in the factory. In the UK, some manufacturers produce such panels but the effects of weather on materials and details of erection on site must be carefully considered.
   
3. Westructure Timber Frame for your timber framed building requirements.
   
   
4. External walls.
   In timber frame construction the framed wall panels carry all the vertical and horizontal loads to the foundations. If brick or block cladding is used, this is supported directly off the foundations but the cladding does not carry any loads other than its own self weight. Light claddings, such as timber boarding, tile hanging or render on mesh, however, are supported directly off the wall panels. For this reason it is important for the timber frame structural engineer to be aware of the cladding type.
5. The stud framework is the vertical loadbearing skeleton of the external wall. The framework consists of vertical studs and horizontal rails. All these structural members must be of strength graded timber, normally preservative-treated to ensure durability. Studs for buildings are most commonly 38 x 140 mm. Larger sizes may be used to provide for an increased thickness of insulation.
6. The studs are butt jointed and nailed to rails of the same section. Studs are normally spaced at 600 mm centres, although 400 mm centres may be used. These spacings ensure an economic use of 1200 x 2400 mm sheathing boards.
7. Sheathing is most often fixed on the outside of the stud frame. With this arrangement, an effective vapour control layer is normally required on the ‘warm’ side of the insulation to limit the amount of water vapour entering the wall panel. The vapour control layer may be a separate polythene sheet or plasterboard with an integral vapour control layer. Sheathing can be fitted on the inside of the studs but in this case, erection procedures and the installation of services needs careful consideration.
   
8. A lining of plasterboard is fixed on the inside of the framing and is part of the inherent fire resistance of the wall. The cavities between the studs and rail framing are filled with mineral fibre insulation. The outer face of the sheathing (or the framing and insulation if the sheathing is on the inside) is normally covered by a breather membrane, which protects the panels during construction and provides a second line of defence against any wind-driven rain that may penetrate the completed external cladding. The breather membrane is usually of a plastic fibre material, strong enough to resist site and wind damage, which is weather resistant but allows the escape of water vapour from the construction. Some types of breather membrane enhance the thermal performance of the wall.
   
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