Expert: Richard Taylor, AIA - 1/25/2012

Question
I see some homes with a deep basement and some with a shallow basement. What normally decide the depth of your footing when building a house. THANK YOU. NORMAN

Answer
Hi Norman - thanks for your question!

Let's start from the bottom and work up - footings are designed to carry the weight of the house down into the ground, obviously.  They're usually wider than the wall above to spread the weight around a little.

How wide?  Depends on the ability of the soil to carry weight; some soils are better at it than others.

But good soil doesn't always appear where you need it, so often you'll have to dig a little (or a lot)deeper to find what's referred to as "undisturbed" soil.

That's depth factor #1.

Number two is something called the "frost line".  That's the underground level at which the ground above normally freezes in the winter.

In Canada, this line's pretty deep.  In Florida...well, there's no frost line in Florida (like I need another reason to head south right now!).

If your footings aren't below the frost line, when the soil freezes it will "heave", moving the footing, the foundation wall, and everything above it.

Absolutely critical to know where that line is and get under it.  Think limbo.

#3 - Money.  Moolah. Dinero.  Deeper foundations and basements cost more.  More digging, more building materials, thicker foundation walls, longer stairs, more heating and cooling...

#4 - Feasibility - building on good, stable soil?  Call the backhoe.  Building on bedrock or sand?  Not so much.

#5 - Personal choice (we still have that in this world, right?) - do you want/need a basement?  In my part of the world, building a home without a basement is relatively unthinkable (we have SO much stuff to store!), but in other regions basements are less popular.

Want to know more?  Take a look at this blog post: http://rtastudio.blogspot.com/2011/10/basement-or-crawl-space.html

Thanks again, hope this helps!

Richard Taylor, AIA
www.rtastudio.com
www.rtastudio.blogspot.com
www.facebook.com/rtastudio