Expert: Richard Taylor, AIA - 1/14/2010

Question
We own a historic home built in the 1850's in the "limestone belt" of southern Indiana.  The foundation is simply large limestone cornerstones with large, squared timbers laid across them for sill beams.  Slabs of limestone were laid between the sill beams and the ground to "seal" between the corner stones.  The sill beam timbers have slots chiseled into them that the floor joints sit in.  The bottom of the floor joists are only 2-3 inches above the ground , so there is essentially no crawl space.  As a result the floors are not insulated and are freezing cold in the winter.  Is it possible to excavate under the house to create a crawl space ?   If so, how should we go about selecting a contractor ?  Also, would I need to make changes to the foundation at the same time ?  

Answer
Good morning Matthew - thanks for your question!

What you're proposing isn't uncommon, and there are specialty contractors who can do it for you.  There are a number of approaches to do this, depending on the condition of the structure and the soil.

One way is to excavate under the house and "buttress" the existing foundation walls - essentially you'd be building a new, smaller foundation inside the old one.  Under the right conditions, this new foundation could be full basement depth.  You'd then insulate the foundation/crawl space side walls just like a new foundation.

Another way is to lift the house completely off of the existing foundation and put it on a new foundation somewhere else on the property - doing essentially what a housemover would do.  Again, this could be a full basement if you wanted it.

As with any old house, this needs to be carefully evaluated ahead of any work - some older homes aren't sufficiently sound to handle foundation changes, and some have hidden damage that you must find first.

Just as importantly, sealing up the underside of a house that's been "exposed" for 150 years may start a chain of events that results in damage to the house.  Moisture control can be a real problem if you don't create the proper air circulation needed to protect the wood members of the structure.  You'll need someone to evaluate your house and what it needs in this regard.

Likewise, introducing heated air to the underside of the house will have an effect on it - wood shrinks and expands with temperature changes.

And any new foundation will also need proper waterproofing and drainage.

So where do you find local contractors who can do this work?  I'd start with your local Historical Society, they may have listings of folks who've done this before.  If that doesn't get it, try Period Homes magazine (www.period-homes.com) and The Old House Journal (www.oldhousejournal.com).  Both have tons of articles on this kind of work (especially OHJ) and should be able to direct you towards people in your area who can help.

You may also find an Architect in your area who specializes in Historic Preservation (try the Architect finder at www.aia.org) - might be worth a few hours of consultation before you dive in.

Hope this helps!

Richard Taylor, AIA
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