Expert: Bruce E. Johnson - 9/5/2008

Question
Hi.  Read your answer to Eric conc:  Pier & Post or concrete slab.  The lumber co. prefers pier & post & since I'm from Florida, I prefer concrete slab.  It's a wooden home to be built w/ the above choices.  Do I pay extra for the vapor thing under the concrete slab?  Which one, Bruce, would have more of a chance of mold, I'm thinking pier & post.  Must be cheaper for p&p if the lumber co. prefers it, right?  I was surprised there is no termite requirement if it's p&p.  There is one, however, for the concrete slab at my expense of course.  In a hurricane/earthquake etc.  which one holds up better?  I thought I read somewhere there is a failure of 3 out of 4 p&p.  So does that mean the p&p will come unfastened & fall down?  Thank you so much.  I'm building this dream home for just myself & my two daughters, don't have a REAL man's opinion.   Take care,  Mary

Answer
Hi Mary, I personally prefer a concrete slab foundation as opposed to a post and beam crawlspace.  Even in a crawlspace I recommend a vapor barrier and termite treatment.  As far as mold etc. goes.  If a crawlspace is vented properly it should circulate enough air to keep these kinds of things from growing.

I can't see why a concrete monolithic slab foundation would be any more expensive than a post and beam floor system.  A concrete slab accomplishes in one fell swoop what a foundation wall, posts, beams, floor joists and sub floor sheathing are needed for a crawlspace.  Even if you have to pay for termite pretreat, which is minimal by the way, and a good 6-8 mil vapor barrier, which is again a minimal cost..it should still be cheaper or as cheap as a crawlspace foundation unless a salesperson is jerking your chain because they are unfamiliar with slab foundations or they are trying to create an added expense to get more money out of you.  

I went to the Hawaiian Tropic website but didn't get a lot of information from it to see how they are built.  From the photos though it does look like most of them have crawlspace foundations. Maybe that is their design formula and they try to discourage changes to it.  I can't say.

I built many a home in the Pacific Northwest using crawlspace foundations but since I moved to Florida in the early 80's I have come to prefer the monolithic slab.  I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com