Expert: Ted Barnhill (Principal, Design45 LLC) - 11/10/2008

Question
I noticed some drywall in the corner of my garage wet.  So I started pealing it back and discovered that the baseplate is completely rotten and about 1 - 2 feet up the studs is also rotten.  Part of the problem is in the corner where I noticed the rotten drywall, on the exterior there is cement steps/slab on the exterior and it looks like there was just nothing put against the exterior wall as the particle board on that side was completely disintergrated.  When I started taking the wall apart the insulation was rotten and the exterior board and then it is sand and fill behind that.  How do I fix this so the exterior does not just rot again?

Answer
Cory,

Sorry to hear about your problem.  As you have discovered, untreated wood doesn't last very long in contact with the ground.  You really only have two choices, either:

A. Rebuild your wall as a below-grade (foundation) wall, or
B. Remove the steps/slab/fill and regrade the area adjacent to your garage.

If you choose A, the wall can be rebuilt with concrete block, masonry, poured concrete, or treated wood.  A treated wood foundation, which consists of treated studs and treated plywood sheathing, may be the easiest to tie in to your existing framing, but will be the most sensitive to eventual rot if the wall isn't well waterproofed.  To provide proper waterproofing and drainage at the exterior of your wall, you'll probably have to remove the steps and concrete immediately adjacent to the garage.  A creative contractor on site may find a way to build this wall "in reverse order" from the inside, but this would be very tricky.

Option B may be the better long-term solution, if it is feasible given your lot's grade and use of the property.

Good luck, and feel free to post any follow-up questions you may have.  -Ted