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How heat affects timber beams. #7741 05/29/01 05:16 PM
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I am involved in an unusual situation concerning a fire damage in a partially stick framed, partially timber framed house. The heat from the fire did not char the timbers, however several 12"x12"x22' vertical beams appear to have split and twisted. The splitting is large enough to stick my fingers into. The twisting is so bad that one of the tenon joints appear to be almost out of the mortise.

The beams are made from high density Douglas fir, structural grade. There is a lot of heart in them as well.

My questions are as follows. Can intense heat cause such warping and splitting and does the alteration compromises the structural integrity of the beams?

My second question concerns whether the beams are compromised aesthetically. The house is a one-of- a-kind project about three years old. It was copied from an old structure in England and great care was taken to insure every detail was perfected. If the heat has affected the timbers, it could be that the fire has prematurely aged the timber beams, or damaged them by aging them too quickly. If the beams were aged too quickly, resulting in the warping and splitting, does this compromise the aesthetic value of the house?

Aesthetics are a large part of the timber framed home's value. Thus, the appraisal of the house may go down in value as a result of premature aging of the timbers caused by fire damage. Of course, beauty is in the eye of the beholder, but someone interested in buying a three-year old timber framed home might look suspiciously on such heavy checking and warping.

If anyone can help me with either of these two concerns, I would appreciate it. Any information as to where I can find an expert that would inspect the beams for a fee would also be appreciated.

C. H.

Re: How heat affects timber beams. #7742 05/30/01 05:49 PM
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It is difficult to do any assessment over the internet.

If the timbers are not charred, it means they were not exposed to fire, otherwise they would be charred. The charring occurs at around 300°C.

The checking and twisting is most likely result of severe drying during the fire in the house. Uncontrolled drying conditions can cause great checks and twist/warp. If the timber contains pith it can be even worse.

Exposure of wood to elevated temperatures for some period of time causes the chemical changes in the wood accompanied by decrease in strength. There were several articles published on this subject.

Regarding the appearance damage, I can not comment on that. But some people like those large checks and aged wood look. I guess it is matter of preference. If you need to get more info, email me dalibor@van.forintek.ca or call 604-222-5658

Dalibor


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