A Garage Inspection

 I was asked to inspecta townhouse. Throughout the evaluation, I ran into a neighbor who informed me that the roofing of another garage,  2 structures down, had actually collapsed the previous winter under a snow load.

So, I chose to keep my eyes large open as I went through the garage.

Above: trusses and truss connections

Some defects you have to browse for, and some are quite apparent. These first 2 problems were apparent from the entrance:

improper modifications; and
improper bearing points.

Trusses can not be changed in any way without the approval of a structural engineer. When you see plywood gussets added at truss connections like these triangular gussets, then a modification of some sort has certainly been made and you have to advise evaluation by a structural engineer. That condition went into the report

Trusses are developed to bear loads at extremely particular points. Common roof trusses must not touch any interior walls and ought to bear only on the outside walls. The 2 trusses at the left of the above picture are bearing on an offset portion of the garage wall.
A part of the structural roofing load was being transferred down chords of the trusses at a point at which they were not designed to support a load.

Above: the connection

Then I walked over and looked more closely at the connections where the trusses connected to the wall and discovered these issues:

inadequate metal adapter (hanger);.
inadequate fasteners (deck screws); and.
incorrect fastener setup (through drywall).

These trusses would have best been supported by bearing directly on wall framing. The next finest option would be an engineer-designed ledger or engineer-specified hardware. Which may have been how they were originally constructed, however by the time I checked them, 24-foot roofing system trusses were supported by joist hangers designed to support 2x4 joists. The hangers were secured with four gold deck screws each.

Gold deck screws are developed to withstand withdrawal. Fasteners for metal connecters such as joist hangers are created to withstand shear.

Withdrawal force resembles the force which would be produced if you got the head of a fastener with pliers and tried to pull it directly out.

Shear force is exactly what's utilized if you take a pair of sturdy wire cutters and cut the fastener. Fasteners designed to withstand withdrawal, such as deck screws, are weak in shear resistance.

So, there were significantly undersized metal adapters fastened by badly under-strength fasteners.

To make matters worse, the screws were fastened through drywall, which doesn't support the shaft of the screw and breaks down the connection even further.

And, when I looked actually closely, I found more truss modifications. The gangnail had been pried loose and the spikes which form the actual mechanical connection were damaged. In their place were a couple of bent-over nails. This condition provided a great loss of strength and this roofing, too, was a prospect for devastating structural failure.

In summary, look carefully at connections for problems which may lead to structural concerns, as some are more urgent than others. Be sure to call these out in your report. Also, all electrical receptacles in garages should be GFCI-protected, without exception.


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