Expert: Richard Taylor, AIA - 8/5/2004

Question
Dear Mr. Taylor, I am planning to build a new home in Southern California.Because of forest fire and earthquake conditions there, what form of homebuilding do you recommend? I have checked out the pros and cons of steel framed homes and ICF concrete and wonder if a combination of the two would be best.I would deeply appreciate your opinion.Sincerely, Pamela Byrne

Answer
Pamela:

Thanks for your question!

I'm sorry to be so long answering, but I've had some problems logging on to the site today!

You've asked a complex question for which there's no simple answer but I'll tell you what I can.

Depending upon where you're planning to build, you might not have many choices in building materials and systems.  CA has a stringent seismic code, and your house will have to meet it.  You'll need an architect or structural engineer for that part of the design.

It's also likely that local codes may prevent you from using some exterior materials (wood shingles, for example) that would contribute fuel to a fire.  Check with local fire codes on this one.

Regarding seismic design, there are a couple of important concepts to consider.  An earthquake puts lateral (side to side) loads on the house, not vertical loads.  It's critical to make the structure shear-resistant - basically, keeping it from falling over when it's pushed from the side.  Also, the house must be solidly anchored to the foundation - many failures occur because the foundation is literally jerked out from under it.

This is easily designed for with both wood framing and steel framing.  They're both flexible enough and structurally redundant enough to distribute lateral loads, and shear walls are easily built with those systems.

Concrete construction is less adaptable since it's a very stiff material.  It doesn't respond well to lateral loading without a lot of reinforcing.  This makes it more expensive to use.  Also, a wood or steel-framed house will be far easier to repair after the quake than a concrete house.

Because of ease of use, suitability for seismic design, and cost, I'd go with wood or steel framing.

If a forest fire engulfs your home, almost nothing will prevent its destruction - you're talking about a 2000 degree fire.  You can, however, secure your house against a less intense fire.

As you know, the best strategy to protect your house is to remove any fuel from the immediate area - clear the site of brush and fallen timbers first (assuming you're allowed to)!

The real problem isn't the structure of the house, it's the exterior materials.  Most house fires in your area that are related to brush and forest fires start when burning embers land on roofs and ignite the roofing materials.  The number one culprit is wood shingles.  There are many fire-rated roofing materials - look into some of those instead.

Same with the exterior of the house.  Wood siding will burst into flame when it gets hot enough, but brick and stone won't.  Ever notice how the brick chimney is the only thing left standing after a house fire?

In short, keep flammable materials off of the exterior of the house!

Steel framing won't stop your house from burning if the fire starts outside - and in a 2000 degree fire, it'll just soften and buckle anyway.  It will, however, help stop fires that start inside the house, especially inside the walls.

So for fire-resistance, I'd rate concrete at the top, followed by steel, then wood.  That's more relevant if you have flammable materials outside, less relevant if you don't.

For seismic design, fire resistance, and cost effectiveness, I'd suggest a steel-framed house with a brick or stone exterior and fire-rated roofing material.  That's the simple answer - find a local architect to help you flesh out the details.

Hope this helps!

Richard Taylor, AIA
Richard Taylor Architects, LLC
www.rtastudio.com