Obtaining and understanding wood i joists span tables can help you to know the correct span needed for your project. The span relates directly to the material and the size of a joist.
What is i-joist wood, though? It is an engineered wood joist product specifically designed to combat common issues with traditional wood joists. Developed for the first time in late 1960s, it is a product that possesses solid strength in terms of weight and size. The primary difference of i-joist lumber is how it is able to supports heavy loads with less amount of lumber compared to a dimensional lumber joist. Per 2005, it was estimated that i-joist is used on half of all wooden light-frame floor construction.
As mentioned, i-joist was developed to help omit common problems concerned by using solid lumber joists. Some of the examples of the problems often encountered by dimensional lumber are twisting, crowing, bowing, splitting, checking, or cupping. The minimal shrinkage and dimensional soundness characteristics of i-joists also help reduction squeaky noise of floors.
That being said, it also does have disadvantages. The catch of using i-joist wood is extremely fast structural malfunctioning when exposed directly to fire, providing less time for building occupants to escape and raising the risk to firefighters.
Now, let’s move to joist span. The span refers to the length covered by the joist between foundation walls or beams as supporting structures. In general, pre-calculated tables are used by builders to determine the proper spans for different spacing, size, and lumbar species. However, it must be consulted with the local building codes every time, since different recommendations might be required in less common circumstances.
Wood i joists span tables and rafters are provided by American Wood Council (AWC). That being said, you can also find other tables and publications by other sources, such as Western Wood Products Association (WWPA).
Majority of joist manufacturers provides wood i joists span tables of their own, which displays the recommended joist size for the desired span. Consumers can get ideas of how far the joist is predicted to move or deflect under a certain load. Different manufacturer usually has different table for every joist type it produces, which can be used by consumers to select the appropriate material according to the maximum deflection as indicated in the local building code.
A thorough analysis of i-joist wood mechanical properties is rather complicated. However, sizing joists using wood i joists span tables is a relatively simple process given that you understand the basic rules that determine their use.