Reusing old Trussess

[Will007]

I've got a friend who wants me to certify that he can use wooden trusses he bought over a year ago to build his new house.

The trusses have been sitting outside the entire time with no cover on them.

They are still in tact but a few hair cracks about 4-5 inches long are noticed on the ends of the wood. This is in Bullhead city, Arizona.

Can he still use these trusses for his house, if so, what does he need to do to remidy the cracks at the wood edges.

Thanks

 

[msquared48]

Were these trusses that he purchased new and never used, or were they used trusses from an old building that was demolished, possibly not from the area. (DESIGN SNOW LOAD DIFFERENCES)

If they were new, then he should go back to the manufacturer for the certification as they would have certified the original design.

If they were used, with the horizontal end checking, I would be suspect of the any shear plate connection where the checking extended into the area of the shear plate. This is assuming that metal shear plate connectors were used.

Mike McCann
McCann Engineering

 

[cvg]

note that manufacturers don't typically certify that the trusses they are supplying are brand new and those trusses may have been sitting around for some time even before they were shipped to your friend. That said, unless you can get the manufacturer to re-certify them, you would need to do some sort of structural analysis to determine if they were acceptable (both size and strength and condition) for his proposed use. Depending on how they were stored, I might hesitate to use them. Were they sitting directly on the ground? Are they pressure treated? Did they ever sit in water? Are they warped?

 

[Will007]

Thanks for your reply. Attached is a picture of the trusses.

Hope this gives you a better idea. He said they were bought new from the Manufacturer over a year ago and he does not want to pay the expensive fee for the manufacturer to recertify his trusses.

Appreciate your advice on this matter.

 

[msquared48]

From your picture, the material looks OK to me - the end splitting is on the rafter tail - but you need to verify the snow loading, and maybe tile too if used?

Mike McCann
McCann Engineering

 

[civilperson]

Not much rain or snow in Bullhead City, therefore the trusses probably are still fine. Prop one up and load with hanging weights while measuring deflection.

 

[bimr]

I agree with msquared48, have the manufacturer certify the truss. That is what is called out in the instructions.

http://www.gov.mb.ca/labour/safety/roofguide.html

Why should you take responsiblity for free. If the truss later fails, you will get sued and lose your friend as well.

Tell your friend that you do not have insurance to cover your work.

 

[VikingEngineer]

I believe that the ends of the lower chords may need to be strapped with galvanised straps to prevent further splitting. It may also be wise to get a specialist to check for rot in the timber. If the timbers have dried out and shrunk, the nail plates may be loose and these may need to be re done or possibly consider bolted connections. I still subscribe to the idea of a load test and think that this has merit.

 

[looksatstars]

I agree with others on the board to get the manufacturer to cerify them, if possible.
It looks as if the water has not damaged them as they were stacked ok. sometimes there is lath in between for air circulation.
I wouldnt worry too much about the checking in the rafter tails. What we used to do to remedy deep checking in timbers is to use epoxy to seal them

 

[chicopee]

The ends of those trusses still appear in good shape. Does not appear to have dry rot. Since the trusses are simply supported, there is no end moment. The ends are primarily affected by horizontal and vertical shear and would have little bending stress. Hopefully the trusses were stored on dunnage with a lot of air space between them. As suggested above prevent further splitting. If your judgement warrants derating the trusses by 10% do it.