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 lumber. Because of the resulting grain pattern, it is also referred to as Edge-Grain lumber.
Plain sawn lumber (pictured right) is more common as it produces more useable lumber from a log. The log is simply cut into thin strips which are then milled to usable lumber. This method is capable of producing much wider pieces of lumber with more decorative grain. Due to the lack of waste, plain sawn lumber is more economical to produce, but is more susceptible to warping due to moisture changes. As the grain is more pronounced on the face of the board, plain sawn is also referred to as Flat-Grain lumber.
Lumber Seasoning
Freshly cut wood contains a high percentage of moisture. As much as 45% of lumber could be water by weight. Due to the structure of wood, this high value of moisture content needs to be dealt with. Green lumber (with a moisture content greater than 19%) cannot be used for construction or finishing purposes as the lumber will shrink and warp as it comes to equilibrium with the surrounding humidity of the air. To mitigate this, lumber must be dried before being used by one of two methods:
During the drying process, the lumber will shrink substantially (up to 12%). This shrinkage is most noticeable across the grain (width and thickness) and is negligible along the length of the board. After the drying process, the lumber is checked with a moisture meter. Boards which have reached a moisture content of 19% or less are considered to be seasoned.
Lumber Defects
Defects can occur in lumber naturally or due to manufacturing processes. Natural defects include knots, pitch, wane, and rot or decay. The manufacturing process can produce defects such as machine burn, surface waves, and cracking, which is caused by drying lumber too rapidly. Lumber may also warp during or after the drying process. Twist, cup, bow, and crook (crown) are some of the ways lumber can warp and is often caused by improper storage of the material. In order to prevent warping of lumber on site, it is important to store lumber in organized, level stacks.
For illustrations of the above defects, refer to Chapter 2 – Lumber in Carpentry.
Lumber Grading
Lumber grading is determined by a number of factors. The type of wood (softwood and hardwood) is first considered as there are different grading systems for each. Depending on species, strength, and defects, softwood lumber is graded at 7 levels, with 1 being the strongest and 7 being the weakest:
- Select structural
- No. 1
- No. 2
- No. 3
- Construction
- Standard
- Utility
While many grades are separated by species, some softwoods with similar characteristics are grouped together for grading, such as S-P-F lumber (Spruce-Pine-Fir).
As hardwoods are largely used in finish applications, they are primarily graded based on appearance. Hardwoods are graded on three levels, with first and seconds being the highest grade:
- First and seconds
- Select
- No. 1 common
Some manufactured products are characterized by the level of finishing. Some common abbreviations that carpenters will see include the following:
Lumber can also be manufactured in specific profiles for a variety of work. Some common profiles are shown below:
Board Foot Measure (BFM)
While many lumber products are sold in specific dimensions (16’ – 2×4 for example), lumber can also be sold by the board foot. Common when buying irregularly shaped lumber such as with hardwoods, or when lumber is sold in bulk from the lumber yard, it is a measure of volume of wood.
In simplest terms, a board foot is equal to a piece of wood that is 1” in thickness, 12” in width, and 12” in length. When calculating a board foot in terms of volume, we can take those three dimensions and find that 1 board foot is equal to 144 cubic inches as shown below:
While board feet is most simply expressed by a piece of lumber with those dimensions, it is worth noting that the BFM comes from the volume not the shape of the board. See below for other examples of boards that contain 1 BFM or 144 cubic inches:
Calculating Board Feet:
There are two primary methods for calculating board feet. Unless otherwise specified, we will use the nominal dimension (not the actual dimensions) given in our calculations:
Method #1
Knowing that 1 BFM = 144 cubic inches, we can calculate how many board feet are within a piece of lumber by dividing its volume in cubic inches by 144. For example, we will calculate how much lumber in board feet are in a board that is 2” x 10” x 120” long:
= = 16.67 board feet
Try the following example using method #1:
***How much board feet are there in a piece of lumber 1.5” x 12” x 96”?
Method #2
A more common approach in calculating board feet is to use the following equation:
This method is used with more prevalence as the use of feet in the length measurement, which is much more common, eliminates the need to convert from feet to inches. For example, we can calculate how much board feet there are in a piece of lumber that is 1” x 6” x 16’:
= = 8 board feet
We can also use this formula to calculate the amount of board feet in a pile of lumber. For example, let’s say we want to figure out how much board feet are in a pile of 26 – 2×8 @ 12’ long:
x 26 = = 16 x 26 = 416 board feet
Notice how the formula for the above does not change for the individual board, we simply multiply the result by the quantity of boards.
Try doing a couple examples using method #2:
***Calculate how much BF are in a piece of lumber 2” x 12” x 14’
***Calculate how much BF are in a pile of 96 – 2×4 @ 10’
Review Questions
- Wood is made of hollow cells held together by _______.
- Which portion of the tree is most resistant to rot and decay?
- Name and describe the trees that each produce softwoods and hardwoods.
- Name five different species of hardwoods.
- Name five different species of softwoods.
- Which sawing method is the most economical and produces greater widths?
- What moisture content must seasoned lumber be at or below?
- What is the primary cause(s) of warps in lumber?
- What is the highest grade of softwoods? Of hardwoods?
- Calculate the BF in the following:
- A piece of wood 2 ½” x 6” x 84”
- A board 1 ½” x 3 ½” x 12’
- A pile of 120 – 1×8 @ 8’