Four Examples Of Roof Truss Defects A Homeowner May Not Know About

Posted on: 19 April 2016

Between a homeowner and a roofing contractor, who should buy roofing materials? You may be afraid that going the contractor route is expensive because of the small markup they add. However, as a homeowner, you can end up buying inferior materials. For example, roof trusses (structural roof framework made from wood beams) can have manufacturing defects that may weaken your roof. Here are four examples of such defects:

Misaligned Plates

The truss connector plate is a light metal gauge that connects different frame wood trusses. The metal plate is punctured to produce teeth on one of its sides. It is the teeth that sink into the wood trusses to join different wood frames.

Each joint has two plates – one on each side of the joint. For a simple connection of two beams, the joint should be centered between the two plates. However, a manufacturing snafu sometimes happens, and one or both plates end up lopsided (one side of the joint having fewer teeth than the other). This weakens the joint, and effectively, the truss.

Missing Plates

As explained above, each joint is supposed to have a plate on each of its two sides. However, you may get a truss joint with only one plate. Mishandling of the truss beams, for example during transportation or loading, can also lead to missing plates. However, it may also happen as a manufacturing defect. Whatever the cause of the missing plate, the joint will be weaker for it.

Large Knots

A few knots are inevitable in any roofing truss. However, manufacturers avoid large knots, so a truss that comes with large knots is definitely a manufacturing error.  The knots weaken the trusses; since the woods are already weak around the knots, they are excellent starting points for cracks or breakages. In addition, driving a nail or embedding a connector plate over a knot results into a weaker joint than you would get if the knot weren't in place.

Wood Imperfections under the Plates

As explained above, a large knot under a connector plate leads to a weak joint. However, a knot isn't the only imperfection that may prevent the connectors from fastening tightly onto the wood. Other imperfections, such as wane or pitch pocket, may also have the same effect. A wane refers to a position of missing wood while a pitch pocket refers to an accumulation of resin. Both of these defects prevent connectors' teeth from sinking deeply into the solid wood, and the results are weak joints.

You can use the information above to evaluate trusses and ensure you have the right materials, or you can just let the contractor handle it. The roofing contractor is less likely to make such a mistake than you because they know how to evaluate roofing materials and where to source good ones. That way you won't waste resources dealing with defective products or processing returns.  

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