Timber frame construction

Timber frame is very much on the ascendancy as a mainstream construction method for dwellings and medium rise buildings in the UK.  Financial and time savings are there to be had providing the method of construction is understood.

 

Using our FAQs, simple guides and highly popular Timber Frame Design Guide below, let us help you get the design right first time.

 

For design consultancy, inspections, testing, third-party certification and training on timber frame, call our technical helpline on +44 (0)1494 569601.  All commercial services are provided by TRADA’s service provider, BM TRADA.

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What is timber frame construction?

Timber frame construction is not a system of building, although there are a number of well-researched systems that use timber frame as a basis.

Timber frame construction uses timber studs and rails, together with a structural sheathing board, to form a structural frame that transmits all vertical and horizontal loads to the foundations.

Platform frame is the most commonly used method in the UK. Each storey is framed with floor-to-ceiling height panels and the floor deck of one floor becomes the erection platform of the next.

For more information, see Timber frame construction, the definitive professional manual for timber frame designers and specifiers.

Other timber building methods include:

• SIPs (structural insulated panels) consist of a layer of oriented strand board (OSB) bonded onto each side of an insulating foam core. These composite engineered products can be used as a structural loadbearing element.
• CLT (cross-laminated timber) uses wood panels in which the thickness is made up of a number of narrow widths of timber laid together with each layer at right angles to the previous layer. These panels can be pre-cut in the factory to form wall, roof and floor elements.
• Engineered stud is a simple way to allow a large depth of insulation to be installed between the loadbearing timber studs used for timber frame wall panels. A number of different types of engineered stud are available, using either I-joist or metal web joist designs. 
• Twin stud is two timber frame stud walls in parallel, separated by a cavity, but only one of these carries the vertical load of the building.

Innovative timber construction gives comprehensive information on each of these timber building methods.

Current timber frame construction incorporates high levels of insulation within structural elements, but clients are now seeking designs that can deliver improved thermal performance. This can be achieved by using:
• deeper solid timber studs
• deep engineered timber studs (typically timber I-joists or open web joists)
• additional layers of insulation material (internally or externally)
• novel construction methods such as SIPs

Options for improving the thermal performance of existing timber frame buildings include:
• improving airtightness
• increasing roof insulation
• upgrading windows
• adding floor insulation
• upgrading wall insulation.

See Timber frame construction and WIS 0-11 Improving the thermal performance of existing timber frame buildings for detailed information on the options available and how to implement them.

All forms of construction need to comply with the fire performance requirements laid down by national building regulations. Timber frame dwellings have no difficulty in meeting the required levels, given correct design, standards of manufacture and workmanship. The following are important considerations:

  • Internal linings, usually plasterboard, limit the potential for a fire to develop and provide the period of fire resistance required by the building regulation.
  • Cavity barriers prevent a fire from entering a cavity and prevent a fire from escaping to an adjacent cavity zone. Their correct installation on a timber frame site is of paramount importance.

Refer to the following for further guidance: Timber frame constructionWIS 4-30 Fire performance of timber frame dwellings, UKTFA advice on construction sites and fire safety.

Sole plates are a very important element in a timber frame building. As the first timber frame components installed on site, their installation has a direct effect on the building’s service life, line, level and plumb, as well as contributing to the speed of construction. Sole plates:
• are an accurate jig for setting out the timber structure
• transfer loads to the foundations through bearing and with the aid of fixings.

Requirements include:
• they must be level and correctly laid out to the sole plate drawing, installed to the structural engineer’s specifications
• they should be preservative treated
• all timber, including sole plates must be at least 150mm above external finished ground level.

Further requirements and information can be found in WIS 1-48 Sole plates in timber frame construction.