Does heat damage wood? 1

[abusementpark]

Does exposure to extreme heat damage wood in any significant way? Or does only contact with fire damage wood?

I'm thinking of wood members that are exposed to extreme heat during a fire, but never actually got burned or charred?

 

[dik]

They can be... there are several older threads about this in the various fora (forums?)

Dik

 

[RFreund]

abusementpark - let me know if you find a good thread or reference, I would be interested as well.

EIT

 

[woodman88]

Here is a pdf that belowzero uploaded in 2008 on heat damage to wood.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[Ron]

Hey dik...we should have done that FAQ we talked about a year ago!!!

The attached paper, by Robert H. White, is a good treatment on the property changes in wood due to heat exposure. Wood does not have to be charred to be affected by heat.

Bob White is probably the most knowledgeable person in the US on fire damage and fire effects on wood. He is at the National Forest Products Lab and has written extensively on the subject.

 

[MiketheEngineer]

Anything above 150F will eventually affect most lumber See APA wood.

 

[abusementpark]

Thanks for the info guys!

So the next logical question a forensic engineer would ask is: How can you figure out if a wood member was exposed to that kind of heat?

I guess you could look at nearby materials that have melted and find out what their melting point is.

 

[MiketheEngineer]

That is one way and the 150F was considered a "long" term temp. Short blasts of heat can be tolerated.

In many very hot fires, the steel will melt before the lumber burns through. I have seen roof trusses still standing where the steel I-beams were melted to floor level.

If the lumber is just soot coated and not charred - you might be just fine - except for the smell. Any charring means replacement.

My 2 cents....

 

[chicopee]

Thinking back about wood framing behind fireplace chimneys, such framing would be affected by the heat transfer thru chimney brickwork and ultimately burn afteryears of exposure.

 

[SteelPE]

chicopee,

I seem to remember seeing a post on another site regarding the repeated exposure of wood to heat will ultimately lower the combustion point of the lumber. This was in reference to the design of fireplaces and was posted on a chimney forum when I was doing research about a zero clearance gas fireplace. This is why the have minimum clearances to members shown in the installation manuals.

I assume this is what you are referring to?

 

[dik]

Ron... I sent you the outline... probably been almost as busy as you <G>.

Dik

 

[dik]

One thread...

thread488-254740

 

[dik]

and another...

thread1066-255252

 

[dik]

Mike... that comes from two causes... As temperature goes up, both the Fy and Es values decrease.

Dik

 

[Ron]

dik...didn't get the outline...please send again.

Ron