Expert: Bruce E. Johnson - 9/14/2008

Question
I'm about to replace the underpinning on a pier and beam house, and in some spots the crawl space floor is 1-2 feet below grade. The plan is to frame up the spaces between piers around the perimeter of the house and then put up Hardy Board. I read that Hardy Board has to be about 6" or so above grade, so I intend to put 2" wide concrete blocks up to grade level in front of the framing in the below-grade spots, backfill, and use stone or a treated 2x6 as a spacer between the blocks and the Hardy Board. There is a drainage issue on some of these below grade areas because the lot slopes away from them, but there are gutters to help control the problem. My question is whether this sounds like a good idea, and if so should I use mortar to join the concrete blocks. Thanks for your advice.

Answer
Hi Patrick, talk about dejavu, I had almost an identical question a few months ago.  I recommend using mortar when laying your "foundation" block mainly because it gives them strength and it gives you a way to level everything up as you go.  I like to use an L shaped flashing on top of my pressure treated 2x6 with the back of the L up and the bottom of the L on top of the 2x6.  Then the Hardi goes on top of that about a half inch above the 2x6.  This gives you good protection against water intrusion and keeps the hardi board from sitting directly in potential moisture retaining areas.  I hope this information helps feel free to write again regarding this ot other matters, sincerely bruce e johnson..bejohnsonconsulting.com