Expert: Richard Taylor, AIA - 11/24/2007

Question
A buddy and myself got into a little arguement about what is stronger in framing a house.( as in a carrier beam for peak in the roof about 36 ft.) I said a well made wood beam is better than steel because in a fire it would hold up longer it woundn,t melt and twist like a steel beam.therefore is stronger??

Answer
Mike - thanks for your question!

By the time the temperature was high enough to deform a steel beam at the peak of a house, the rest of the house would be ashes - so it wouldn't matter!  Steel can deform in a fire, but a fire that intense would completely destroy the wood frame of the house.

More importantly, if the steel beam were supported on wood posts, they'd be long gone before the steel deformed.

A solid wood member will develop a "char" on the exterior that will help it resist additional damage, but again, in a fire hot enough to deform steel, all wood members would be long gone.

In terms of strength alone, steel will span a much greater distance than wood for members of the same depth.

But none of this really matters; steel isn't nearly as easy to work with in house framing as wood.  It is difficult to make wood-to-steel connections in the field and easy to make wood-to-wood connections.  Steel is often used in wood frame construction, but it's usually restricted to the first level, and maybe a few other special conditions.

If fire damage is a concern, there are fire-retardant treated wood materials that you can specify, or even better, use light-gauge steel framing for the entire house.

Hope this helps!

Richard Taylor, AIA
www.rtastudio.com
www.rtaplans.com