Wood frame construction is one of the most widely used methods to build residential, commercial and industrial buildings. Wood frames are not only very economical to build but are also resistant to extreme climatic variations, and offer residents a high degree of comfort. Added to that, wood frames are sustainable and absorb carbon and offset greenhouse gasses.
Wood frames can be used to construct different styles of buildings and there cannot be any restriction on architectural possibilities when wood is the medium. In order for a wood building to perform its expected functions, it is necessary to construct it judiciously and this can be achieved by using sound construction and erection practices. For instance, wood frames are light in weight and hence it does not require cranes and other heavy machinery for the erection process therefore contributing to the economic aspect of construction.
Foundation for Wood Frames
Based on the type of soil and wood frame loads, a suitable foundation is specified for construction. Footings should be deep enough to avoid frost action in winter. The ground needs to be sufficiently compacted if the structure is constructed in an area where root trees have been removed or filled materials are placed. If the wood frame is constructed over poor soil, treated wood pile with wood or concrete sills can be used.
By and large, two types of foundations are widely used for wood structures: namely concrete foundation and pressure preservative treated wood foundation which are shown in Fig. 1 and Fig. 2, respectively. Apart from these, free standing pier, piers with curtain walls, and pier supporting grading beam can also be utilized.
Methods of Wood Frame Construction
After the foundation has been laid, construction of wood frame structure begins. There are various types of techniques that can be used for the construction of wood frames. Suitable construction technique should be selected for a given wood structure:
1. Platform Frame Construction
It is an easy method and suitable for the construction of houses. In this technique, first-floor joists are covered with sub-flooring to create a surface upon which exterior walls and interior partitions are erected. In the system, wall framing can be assembled on the floor and the entire unit can be tilted into its place.
2. Balloon Frame Construction
It is another method of wood frame construction which although is a bit less popular compared to platform frame construction, but is utilized when the conditions ask for it. In this method, exterior wall studs and first-floor joists are supported by anchored sill. The exterior wall studs are continuous to the second floor. The second-floor joists are supported by ribbon strip which are inserted into the inside edges of exterior wall studs.
3. Plank and Beam Frame Construction
In this framing method, beams, whose ends are supported by posts, are spaced at a maximum of 2.4m and planks are used to cover floors and roofs. The posts provide wall framing and planks act as subflooring and roof sheathing. Wall sheathing is attached to supplementary framing between posts. Roof and floor loads imposed on beams, then get transferred to the posts and are finally received by foundations.
4. Truss-Framed Construction
In this frame construction method, roof truss, floor truss and metal anchors are used to build strong wood frames. Outstanding advantages of trussed frames are substantial rigidity and wider spacing of roof and floor supporting members.
Types of Fastenings for Wood Frame
There are various fastening means which can be selected based on the size of wood elements and exerted loads used to attach different elements of wood frames together. Most common fastening techniques are discussed below:
1. Nails or Combination of Nails, Anchor and Additives
Nails or combination of nails, metal framing anchor, and construction additives are used to fasten framing lumber and sheathing panels.
2. Ring or Shank Nails
Ring or shank nails are used when high loads are to be supported
3. Nailed Joints
Nailed joints are used when loads act at right angles to nails, but it should be avoided if loads act parallel to the nail.
Wood Protection Measures
Provision of proper means to protect wood is an indicator of good construction practice. Wood frame elements, specifically all the foundation members, shall be protected against decay and termites.
Basic protection measures include the removal of tree root in areas around the structure prior to backfilling, carefully tamp loose backfill to decrease future settlement, and provide certain degree of slopes at foundation and over the building to force water away from the structure.
Finally, all wood structural elements shall be treated based on the exposure to weather and closeness to ground.