2006 Building Code Changes
On July 1st, 2007, Washington State adopted the latest versions of the International Building Code (IBC) and International Residentail Code (IRC). In simple terms, the IRC applies to single-family homes, duplexes, and agricultural buildings in lower snowload conditions, and the IBC applies to everything else. While it isn't quite that simple, it is a workable definition.
Both the IBC and the IRC incorporate a very significant change to roof truss design as well as a wide variety of minor changes.
The code now states that any space big enough to be used for attic storage must now be designed to carry that load whether it is intended for storage use or not.
THE KEY CHANGE
The code now states that any space big enough to be used for attic storage must now be designed to carry that load whether it is intended for storage use or not.
THE ACTUAL CODE
''Attics without storage are those where the maximum clear height between joist and rafter is less than 42 inches, or where there are not two or more adjacent trusses with the same web configuration capable of containing a rectangle 42 inches high by 2 feet wide, or greater.'' -IBC Revision Table R301.5, footnote ''b.'' (there's more, but that's the key bit)
THE TRANSLATION
If you can put a 2'w x 3'6''h box into a space that spans two or more similar trusses, we need to design it to carry an extra 20 pounds per square foot across those areas.
THE EFFECT
For the most part this is not an issue. The loads get a little bigger at the ends of the trusses, the walls take care of it, and you're good. The cost increase on a truss is fairly negligible as the truss is already carrying 42 pounds per square foot or more for structure and snow loads along its entire length.
However, when a whole line of trusses are hanging into a girder, which is then resting on a beam, these loads can add up quickly. Also, when a house is fully engineered, these additional loads are unwanted.
TCT has a low-cost solution.
We introduce vertical or horizontal ''blockers'' to break up the non-storage space. Another value-added solution from Tri-County Truss.
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