Get tips on how to fix rotting wooden floor joists. Learn how to check your wooden floor joists for rot and how to replace or sister these joists to prevent further damage.
LESLIE: Heading to the great north to talk to Gary in Alaska about some rotting wood . Tell us about the problem at your house.
GARY: Well, what it is, is a little, single-story partition on the house where best I could guess is 2x10 or 2x12 set into the cement pad and it sticks out four or five inches into the soil and it’s slowly sinking because it’s rotting.
GARY: And it’s level with the pad and I can’t figure out why it was built that way or how to stop it.
TOM: So your sense, Gary, is that the wood was actually built on top of the soil?
GARY: Partially, yes; but like oversize.
TOM: What you’re going to have to do here is a couple of things. First of all, you have to cure the soil-to-wood contact and depending on how you’re grading is around the house you need to try to get that lower so that you don’t have that contact anymore. The second thing that you really need to do is to open this up.
The easiest way to do this might be from the outside. Even though it sounds fairly destructive it’s generally easier to take siding off than it is to take flooring out. And in doing so you can examine the condition of the floor joist. If it turns out that the ends of those joists are severely rotted, what you can do is sister those joists and that refers to the practice where you put a new beam next to the old beam, attach them together and then the new beam carries the weight of the old beam. It has to go back deep into the house well over that cantilevered wall by at least two-thirds of the distance that it overhangs the wall.
LESLIE: To structurally  take that weight.
TOM: Exactly, and that would be the correct way …
GARY: I can dig the soil away pretty easy; that part.
TOM: That would be the hot ticket. If it turns out that it’s deeper there than the rest of the yard, then you want to sort of install like a retained area there. It’ll look almost like there’s a trench against the house but it’s OK as long as once the soil starts it runs away.