wood trusses subject to house fire

[m1208]

I have a single story house with fire damage that started in the wall electrical panel. The manufactured wood trusses in the attic space are approximately 30 feet long and spaced at 2' on center. I see lots of smoke damage to the top chord and web members of the trusses, but no smoke damage to the bottom chord because of the ceiling insulation. I scratched the smoke off one of the roof truss member and the wood member was fresh and smoke was only on the surface. Generally if the wood is not charred more than 1/16" on the surface and has only smoke damage, then I do not replace the truss and only clean the smoke damage. Regarding the wood, the NDS states that: “Prolonged heating to temperature above 150 F can cause a permanent loss of strength”, but i do not know the temperature in the roof attic space at the time of the fire. Let me know what you think.

 

[phamENG]

Trusses in fire damaged buildings have to go, period.

Heat rises. If there was 400+ degree air and gasses in that house, they went into the attic. If there was any charring at all - even just a little on the surface - then the actual damage goes deep enough to render the entire section essentially worthless for structural purposes. And when you consider the truss plates only penetrate 1/4" or so and they are made of a heat conductive material, it's not a leap to say the wood that the truss plates are holding together won't be up to the task even if there is sufficient section otherwise.

 

[Greenalleycat]

I'm with pham on this one.

You should also give careful consideration to the context behind your engagement - I'm assuming this is an insurance claim
What are the homeowners' entitlements under their insurance policy?
I would expect that replacement of smoke-charred timber would be an insurable loss even if you weren't 100% certain on structural damage
It is an aesthetic issue that screams 'this fire repair wasn't done properly' and could contribute to a smoky, smelly roof space longer term
I assume the insulation is all going to be replaced?

 

[XR250]

https://www.solutionengineering.com/wp-content/files_mf/1592249547TrussesinFire51420.pdf

 

[dvd]

This is a relevant USDA publication - [URL unfurl="true"]https://www.fpl.fs.usda.gov/documnts/pdf2005/fpl_2005_ross005.pdf[/url]