In these two houses, trusses display their lightweight strength.
Framing long spans for flat or nearly flat ceilings and roofs with wood presents a problem, because the weight load that must be allowed for usually requires large beams--yet as the beams get larger, they get heavier, compounding the problem. But lightweight trusses--made of components in tension and compression--can handle great loads over long horizontal spans, with little deflection. Owner-built Howe trusses: tie rods and standard lumber
At left, Pauline and Joe Kaslake of Phoenix built their own trusses as part of an extensive house remodel designed by architect William P. Bruder. They chose a from known as a Howe truss; in a larger form, it was the most widely used type of truss for covered wooden bridges in the late 1800s and early 1900s. The Kaslakes used standard lumber; threaded steel tie rods bolted diagonally to custom-made steel U-brackets bring the trusses into tension.
Over a living room--dining addition, the trusses support a tar-and-gravel roof with rigid insulation and an exposed plywood ceiling. The roof slopes down from the perimeter walls to a central steel-clad concrete support cylinder; its hollow core acts as a rain downspout, directing water to a drain under the house.
Outdoors, the trusses continue overhead, creating a decorative fan shape and supporting only lightweight shadecloth. The clear spans on the inside walls run 32 feet; outside, they run up to 20 feet. Ready-made Warren trusses: steel tubing and 2 by 4's
Architect Ernest Nickels used prefab trusses of steel tubing and 2 by 4's to form the roof and trellis for the studio addition to his Tempe, Arizona, house pictured on page 105 and below. The ready-made units, known as Trus Joists, are usually available by special order at larger building supply yards.
Each of these triangulated Warren-style trusses rests on only three points: the posts in front and posts built into the front and back studio walls. That's all the support the trusses need. To create the 16-foot clear span inside and support the roof by conventional means would have required solid 6- by 16-inch beams, costing about three times as much.
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|Date:||Feb 1, 1984|
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