Expert: Richard Taylor, AIA - 4/20/2004

Question
I bought a parcel of land in Talkeetna Alaska (115 miles northwest of Anchorage).  My plan is to build a large 4 room cabin for us and 4-6 one room summer rentals.  Because I love books and will not have TV, I have considered using a slab foundation.  Can a slab be used on land with permafrost? I also plan to make every thing important wheel chair acessible. What is the strongest type of foundation.  We also have to consider that Huge earthquakes are likely.  No building is truly earthquake proof.  The FAA building in Anchorage was "earthquake proof)  It came though the 1964 Good Friday Quake better than most highrises but it still sustained quite a bit of damage. Thank you for any help you can give me.

                         Mary Alice

Answer
Mary Alice:

Thanks for your question!

The problem with putting a slab foundation on permafrost isn't the structural stength of the slab - it's more than strong enough if done properly - it's the heat from the slab.  Eventually, the slab will gain enough heat from the house that it will start thawing the ground beneath.  Not enough to melt the permafrost, but enough to cause the slab to settle some.  That would be disastrous for the house!

As far as seismic resistance is concerned, you need a local engineer involved if you want to minimize earthquake damage.  The structural details necessary to make a home earthquake-resistant are important and must be calculated for the individual project.  There isn't any blanket earthquake template.  It'll also cost more, but you have to measure that against the potential loss in a quake.

What do other buildings in the area use?  How have other foundation types in the area fared in quakes?  I'd suggest taking advantage of local knowledge if you can.  Certainly there are local builders who've done this before.  You might want to call them and ask how they've dealt with it.  Otherwise, contact a local engineer or architect to get the engineering you need.

Hope this helps!

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