I need to fill in the carport which is attached to the house. Framing, doors, wiring, etc is no problem. The problem is the floor of the carport is a concrete slab and I want to make sure there is no water penetration under the exterior walls. I live in a wet climate (Vancouver B.C.) and my concern is if I just use tar paper under the wall plate and then 2×4 framing ,sheathing, tar paper and siding, I may get water seepage at ground level. Is their another solution without building an 8 to 12″ high cement pony wall first then frame on top of that?
the Old Guy
Replies
You could place a piece of composite decking or some such under the bottom plate. Depends on how much elevation you feel you need.
Thanks to all, the concrete block idea will work fine, the slab is on grade with the yard, so I was thinking of excavating for a run big O down the side for better drainage as well. Vancouver gets 80 plus inches of rain per year and if this doesn't work i will build an ark.
the old guy
I thing just one course of concrete block on top of slab and then use
reg. wall construction
Short concrete stemwall, or concrete block. Anything else puts your framing and your siding at grade, where it will rot out.
Lay a course of block.
Almost every garage I've framed on in the last 30 years was built on top of at least one course of block. You could lay it directly on the concrete slap and that will get the wood off grade the minimum required distance.
Bob's next test date: 12/10/07
A couple of things to watch for if you pour a curb or put a course of block up before framing. I'm on Vancouver Island and have worked on a lot of houses where this was done. Over time the outside grade tends to build up until it is above the level of the slab. No matter how good the bond, the slab/curb intersection will probably leak.
Also, once the outside grade covers this joint, it is hard to see that the curb is sitting on the slab and is not a foundation extending to a footing. I've seen quite a few additions built on these in the mistaken assumption that it is loadbearing.
I'd be more inclined to make sure the grade stayed 4" below the top of your existing slab, frame on top of a plastic sill gasket, and run a piece 6" flashing on the outside of your sheathing and down the slab 2".