What is Dry Rot and How Do You Fix It?

“What the heck is dry rot and how do I fix it?” That was the question I found myself asking several months into home ownership. Overall, owning a home has been a great experience, and in most cases we got what we expected. We paid for a home inspection during escrow, and also had access to a recent prior home inspection report (our house had been in escrow before but that sale never closed, thank goodness). We knew there had been some issues with dry rot in the siding. But the siding had been replaced. According to the previous owner’s disclosure forms, all the damage had all been repaired. Our home inspection didn’t turn up anything new. It wasn’t until we started to pull up the nasty old carpet in our den that we realized that we had a problem.

Uh oh. The subfloor had white stains on it and the wood crumbled easily when poked with a screwdriver, or even just a fingernail. The problem was worse than that – it had extended into the header below the floor, which crumbled completely apart when we scraped the wood.

Of course I had heard the term “dry rot,” but I didn’t really know anything about it. What is dry rot? How do you fix it? As strange as it seems, dry rot is actually a type of fungus that can get established in wet wood. Weirdly, “dry” rot doesn’t happen in really dry wood – the wood has to be moist. In our house, dry rot occurred where there were leaks. Even where the leaks had been fixed, the dry rot remained. Apparently, once the fungus takes up residence, it can survive a wide range of conditions by staying dormant when it’s too wet or dry. Once the dampness of the wood returns to the ideal range, the dry rot starts to grow again. Creepy!

Since our problem was structural, we hired a licensed, qualified contractor to make the repairs, and I recommend that you do the same.

I’ve never done this type of repair, and even though I’m pretty handy, I would NEVER tackle a structural problem on my own – I wouldn’t be able to sleep at night for fear our house would fall down! Our contractor did a lot of work to provide another means of structural support when he was replacing our dry rotted header. Here’s an example from a different part of the house, where he used a beam to support our deck while he replaced the ledger.

Here are the basic steps our contractor used to fix the dry rot:
1. Expose all the dry rot by taking off the siding, insulation, dry wall, whatever. All the damaged wood needs to be replaced.
2. Cut out all wood that’s been damaged. (Hire a contractor, especially with anything structural! Don’t cut anything structural!)
3. Treat any wood that looks like it’s been exposed to the dry rot fungus but isn’t otherwise damaged (i.e. it is still strong), to impede the spread of the fungus.
4. Replace the wood that was removed. This can be tricky, especially with structural stuff.
5. Get rid of all the dry-rotted wood and dispose of it away from any other good wood! We burned ours. It was cathartic.
6. Put everything back together.

Yeah, fixing dry rot is a major pain. And it costs a lot of money. At least, that’s been my experience. Here are some more of our dry rot photos for your viewing pleasure.

All of the dry rot we’ve found in our house has been repaired by a licensed, qualified contractor. (Doesn’t that just sound reassuring? Licensed. Qualified.) We’re trying to prevent future problems by keeping our house weatherproofed with good caulk, paint, and roofing. We’ll probably always have little problems that come up here and there. One thing we learned along the way: dry rot spreads slowly; fix it when it’s still a small problem. Isn’t that true of so many things?

Dry rot is a very common problem. See how others have tackled the problem here, here, and here.

Make me feel better and tell me you’ve had dry rot problems too! Have you fixed them on your own? Or did you hire a professional?

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