Chapter 30, Problem 30.1Q

To determine

The four common types of lumber used for framing and different qualities of structural lumber by using internet.

Explanation of Solution

Southern pine (SP #2), Douglas fir−larch (DFL #2), Hemlock-fir (Hem-fir #2) and Spruce-pine-fir (SPF #2) are the most common forms of framing lumber. #2 is applied to each species. The number refers to the species grade value. Only #1 or #2 grade lumber is commonly used as framing lumber.

The different qualities of structural lumber are as follows:

• Durability: Strong lumber should be sufficiently durable to withstand the acts of physical agencies, biological agents, chemical agents etc.
• Strength: Resistance to failure is strength. A good lumbershould be strong enough to bear loads that act on it and should not collapse readily.
• Hardness: The resistance to penetration is hardness. Strong lumber should be workable and robust.
• Toughness: The resilience to unexpected shocks and vibrations is toughness. A strong lumber should be solid enough to withstand sudden vibrations and impact loads.
• Structure: The lumber is said to be a fine lumber if it has a uniform structure. lumber fibers should be firm and straight.
• Defects: It is said that a lumberis fine if it is free from defects caused by natural forces such as shakes, knots, burls etc.
• Fire resistance: lumber fire-resistance is very weak. Dense lumber provides the most fire resistance of all forms of lumber but only up to some constraints.
• Mechanical wear: pavements, floors, etc. made of lumber are continually exposed to traffic loads. Therefore, strong lumber against abrasion or mechanical wear does not easily deteriorate.