There is a long history of timber frame construction in Britain, especially for the creation of temporary or low status buildings. In recent years it has become an accepted method for the construction of houses and other buildings. The walls, floors and roofs of a building are formed from engineered or sawn timber and create a structural frame which is then covered and protected with sheathing and cladding. This article looks at some of the reasons this method of construction is so widely used in the UK and some points to consider.
How timber frame works
Vertical members called studs and horizontal members called rails make up wall panels, and together with sheathing boards, create rigidity and help to form the frame. Panels are loaded and carry the vertical loads down to the foundation. Insulation is placed between the studs, and a protective membrane is placed on the exterior of the frame. The insulation may be further supplemented with a layer on the interior of the frame.
The finished interior of the frame is protected with plasterboard and helps to provide fire protection.
Offsite Manufacture
Factory production of wall frames helps to ensure frames are true and accurate. Factory production of panels may include the formation of window and door openings, which helps to ensure a neat and accurate edge. Wall frames are produced in sections, and when completed, are transported and assembled to form the external walls of a building.
Speed and Programme Certainty
When a frame is quickly constructed, other trades can begin sooner, e.g. roofing, first fix, and services. Reduced reliance on early wet trades aids programme, as does the shorter drying time of the wall structure.
Although the advantages just described support programme, they hinge on a good sequence and communication of details between frame manufacture and erection. Changes at a later stage can undo the benefits.
Thermal Performance
It is relatively straightforward to design a timber frame wall to achieve high thermal performance, as timber has a good level of thermal insulation and the frame structure allows space for wall insulation. Therefore, the overall wall thickness can remain within reasonable limits. Attention to detail and good design to achieve airtightness and good integration of thermal bridges help prevent heat loss and improve comfort.
Sustainability
Timber is a good and renewable construction material, as it stores carbon during its growth. Through offsite manufacture, precise control of components can reduce waste, and carbon footprint.
Moisture Management
Moisture is timber’s main enemy, and so good detailing and protection of the material during transport and storage is imperative. Weathertightness of a frame should be achieved as soon as possible to prevent moisture ingress. Cavity trays and other details help achieve this.
For vapour control layers, joints need to be fully sealed and the number of penetrations kept to a minimum. During construction the opportunity to incorporate damp proofing measures should be taken.
Fire safety
The spread of fire and smoke is a major consideration during the design and construction of all buildings. The use of fire stopping, cavity barriers and other fire resistant linings are positioned within timber frame designs to help achieve this.
Sound control
Thought must be given to the control of sound transfer between dwellings for any building type. Timber frame designs are able to effectively address movement of sound by incorporating special layers, cavities and resilient fixings within walls and floors.
Design flexibility
It is crucial that building designs have the ability to respond to the flexibility of changing use, requirements and needs as well as keeping pace with changing building regulation expectations.
Timber frames are highly adaptable to various architectural styles. Compared to traditional methods, the greater ease of adjusting internal layouts, and relative lightness of the structure, can offer an advantage in accessing building sites with more challenging ground conditions. Timber frame is also often the preferred method of extension construction, due to the associated benefits of speed and disruption.
Working with other trades
Service openings in timber frame should be planned in advance, to allow for structuring services to be routed through panels. Joists with preformed openings can simplify the process. Structural members can not be notched, and should not be drilled, except under design guidance.
Quality on site
Factory manufactured panels require expertise to erect. Bracing and temporary supports should be removed once the frame is protected from the elements. The frame can help to achieve various building regulations, and Inspections during key stages, before the frame is covered by finishes can help verify cavity barriers, and other details, are in the correct position.
Looking ahead
The growing emphasis on the need for well built, efficient homes suggests a continued major role for timber frame construction in the UK. However, the frame on its own will not address fire, acoustic or other related needs.