Installs Materials, Fastners, Adhesives, and Connectors
Installs Materials, Fastners, Adhesives, and Connectors
Chapter A7 – Installs Materials, Fasteners, Adhesives, and Connectors
Prerequisite Knowledge:
Topic 1 – Identify Wood and Lumber Used in Construction
The Structure of Wood
Wood is made of many fibre-like cells which are composed of cellulose and held together by lignin. The tree grows in layers which produce distinct rings composed of summer and spring growth. As the cycle repeats itself each year it produced what are referred to as annular rings. Within a log, there are two distinct regions called sapwood and heartwood (see figure 3 below). The sapwood, which is the outer area, is the active region which is responsible for transporting nutrients to the tree and is lighter in colour. The heartwood rests in the inner portion of the log. It is darker in colour and is inherently more resistant to decay.
Identifying Classes and Characteristics of Wood
Lumber is divided into two classes: softwood and hardwood. While the woods hardness is certainly a characteristic of these two classes, they are actually defined by the type of tree that produces it. There are two distinct types of trees:
Characteristics of Select Species
Oak (hardwood) – There are two distinct types of oak: red oak and white oak. Red oak is pinkish-brown and open-porous whereas white oak is greyish-brown and lighter in colour with closed pores. White oak is more resistant to rot than red oak.
Maple (hardwood) – White to pale brown in colour, it has a close, evenly textured grain. It is susceptible to rotting under moist conditions.
Birch (hardwood) – The most abundant and common hardwood in western Canada. It has a white to pale brown colour with a subtle grain. It is very susceptible to rotting under moist conditions.
Walnut (hardwood) – A prized hardwood, it is of dark brown colour. A very dense and hard wood which is relatively expensive.
Teak (hardwood) – A pale, golden brown coloured wood, it is extremely resistant to rot due to its natural oils.
Douglas Fir – One of the strongest of softwoods, it is pinkish-brown in colour and has a very pronounced grain. It holds nails extremely well and is moderately resistant to rot.
Western Red Cedar – Known for its distinct pleasant odour, cedar is a deep brown to pinkish-red in colour. It is naturally resistant to rot and used for exterior finish applications.
Spruce – The most widely used wood in framing, it is pale yellow to white in colour. It is moderately resistant to rot but is susceptible to warping with changing humidity.
Lumber Cuts
There are two general methods for how a log is sawn into useable lumber: quarter sawn and plain sawn (pictured right).
With quarter sawn lumber (pictured right), the log is broken up into quarters which are then run through the saw to produce boards. While this method produces more waste than plain sawn lumber, it produces lumber with the grain perpendicular to the face of the board, which minimizes the effect of moisture changes and warping on the