Topic:  Timber;

Wood construction is common for many single-family houses throughout the world. In areas where timber and wood materials are easily accessible, wood construction is often considered to be the cheapest and best approach for small housing structures.

WOOD FRAME CONSTRUCTION:

A typical modern wood-frame house consists of a reinforced concrete strip-footing foundation, whereupon a platform is constructed of joists covered with plywood or oriented strand board (OSB) to form the ground-floor level of the house (also known as platform wood-frame construction). This platform is connected directly to the foundation with anchor bolts. On this base, the exterior and interior walls are erected. The walls consist of a horizontal sill plate with vertical timber studs with board or panel sheathing nailed to the studs on the outside of the building (Figure 4). After the first-story walls are completed, the second-story floor is constructed, which, in turn, acts as a platform for erection of the second-story walls. This process is continued for all the stories. The roof structure typically consists of prefabricated trusses, which are covered with sheathing and roof tiles (Rainer and Karacabeyli 2000).

The standardized wood-frame structure of today is now augmented by a wide range of compatible standardized components, such as doors, windows, electrical and plumbing fixtures, and the like, which are designed to be easily installed in the wood structure. Because wood-frame walls are hollow, alternative levels of insulation can be installed enabling any climatic conditions to be accommodated. Plumbing, heating, and electrical services are easily installed within the walls, in the open spaces above ceilings, within the floor structure, and in the space between the first (ground) floor and the ground below. Wood-frame houses can be up to three stories in height, as per typical code limits. 

he vast majority of residences in the USA, Japan, and Canada are wood-frame construction, as described above.  Canadian one-story residences are often non engineered constructions, which differ from the USA, Japan, and the Russian Federation’s government housing, where residences are engineered by an architect. 

Platform construction detail in
Canada (WHE Report 82)

USE AND COST:
Today, wood frame is used for approximately 90% of the houses constructed in the USA, predominantly in suburban regions. Costs vary greatly by region and house design, and range from about 650 US$/m2 to 2200 US$/m2 (WHE Report 90, USA), excluding land cost.   The cost for a single-family residential house in Japan ranges from 1100 US$/m2 to 2800 US$/m2 (WHE Report 86, Japan).

STRUCTURAL SYSTEM:
In the typical wood frame house, gravity loads are accommodated by wood “studs,” commonly placed at 16 inches (approximately 400 mm) centers. Floor and roof-framing members are commonly 2 inches (50 mm) in thickness and may be from 6 to 14 inches (150 mm to 350 mm) in depth. Lateral resistance is provided by a shear-wall system consisting of plywood or manufactured wood panels (particle board) nailed to vertical studs, creating shear walls (Figures 6 and 7). Today’s wood frame construction is highly codified and regulated in the USA (WHE Report 90, USA), with a generally good standard of inspection by suburban local building departments in earthquake-prone regions. In smaller towns and rural areas, quality control may be lacking.

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