Thread: Warped truss member

Found some truss members that appear to be warped and./or bowed...how common is this and would you direct to general contractor, or structural engineer.

thanks,

sid

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I cant tell by the picture, how many are bowed?

The two in the picture

How many did you have and were they all located in one area or scattered throughout the attic?

Richard, it was just those two in the picture. All others were okay.

It is not common to me. I would say that a SE has to design a repair. In my mind, those webs are seriously weakened.

They may be bowed because the trusses were set out of alignment with the others, or some poorly selected lumber, but I would not ignore that. Without the webs there, you've got 2 long 2X4 rafters, probably with weak butt splices near the middle.

A typical truss repair is to sandwich the weak sections between plywood with plenty of nails. It's not scientific, but it works good.

How is the passive roof ventilation? the pic appears as the blown in insulation is right up to soffit.Many times poor ventilation causes the trusses to react to conditions, not to mention lumber is planted and harvested in 20 years so you have larger growth rings and molecular cells that are effected by humid conditions meanining shrink, bow, twist ect.

From what I have seen in the past, the wood used to make trusses is high quality lumber, no knots, 4 corners, clear smooth grain.
In the photos shown, the lumber looks like typical framing lumber.
I think the truss manufacturer used a poor quality lumber.
There are likely other problems that have not showed up yet, call for SE.

I doubt this was caused by loading or by environment conditions. I suspect the two trusses were mishandled in transit. It is very easy to fix the bow, and the builder should do so. The length change with straightening will not change the shape of the supported roof elements visibly, tending only to make the roof flatter.

I add support elements to trusses for practical reasons, only improving their stability. Here is one photo.

The dark reinforcing 2x4 was existing. I add hand holds, decking and shelves. Modest loads are well-distributed.
Photo
(edited for finding photo from pasted link, since the inserted Picasa image didn't appear)

I ran into a similar situation a few months ago. One side of a duplex had a roof leak. I inspected the property about a month after the new roof had been installed and found the soffit vents 80% plugged with insulation, no ridge venting and the single gable vent had never been fully opened. In addition, the bathroom vent terminated in the attic -- common around hear.

In addtion to mold, I found about 1 in 5 truss members were bowed. I suggested venting improvements and having a roofing contractor streighten the truss members and install purlins for lateral support.

I did a followup, about a month later. The seller had opened the gable vent and installed ridge venting. The attic area had dried out however the truss members were still bowed --- maybe less but I did not take detailed before and after measurements so not really sure. I again suggested the bowed truss members be looked at by a licensed roofing contractor.

There should be a strongback across the trusses - a 2x4" attached across the trusses.