We recently decided to replace the outdoor deck on our house. When we pulled off the ledger board that had been attached to the house, we discovered the builder had neglected to use flashing. The wood siding seems to be rotten and we’re not sure how far the damage goes. What now?
It’s disheartening to think a builder would overlook something so basic as flashing. To be charitable, your deck builder might have been a previous homeowner who just didn’t realize how important flashing is.
But whatever the reason, you may be forced to deal with rotten sills – an unfortunate fact of life in many old houses.
Your first step should be to peel away damaged material and find out how extensive the problem is. My own old-house adventures have taught me there’s usually more rot than first appears, and all of it has got to come out before you can rebuild.
Mold and insects both prosper in wet wood. And, just as troubling, decaying wood has virtually no structural strength. It can lead to a variety of unpleasant symptoms around your house, including floors that bounce and sag when you walk across them and crooked door and window openings. Water damage is really not something you can afford to be casual about.
That’s the bad news.
The good news is that repairs are simple if the damage is limited to siding and sheathing. Really.
Take off enough siding to completely expose the damaged sheathing, then cut back whatever sheathing appears rotten. Make the cuts with a circular saw over a stud so you’ll have something solid to nail new sheathing to – but remember to pull all the nails in the cut line first -- and make sure to wear safety glasses.
Don’t be surprised if the framing beneath the sheathing has some problems, too. Use an ice pick or a sharp knife to test the sill and any studs that look punky (It should be difficult to press the tip of an ice pick into the wood more than a fraction of an inch).
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| An ice pick - the old-house carpenter's weapon of choice for probing old sills and floor joists. |
Any soft, spongy wood you come across should be cut out and replaced. Just how you accomplish this depends not only on your appetite for hard work but also whether your house has a timber frame or was built with dimensional lumber.
In contrast with modern framing, a timber frame – also called post-and-beam – is made from large, heavy pieces of lumber often joined with mortise and tenon and dovetail joints. Because of their heft, individual pieces can carry a greater structural load and are often spaced relatively far apart. When rot invades the frame, the pieces tend to be bigger and harder to deal with but there are fewer of them.
Stick-built houses are made from sawn dimensional lumber, usually placed every 16 inches. Individually, the pieces are lighter, easier to handle and readily available at any lumber yard. On the down side, there are more of them to rot.
In either case, the basic aim is the same – cut out all rotten wood and replace it with new material. The danger here is making this process sound simple. Don’t kid yourself. Yanking out a stretch of bad sill in a 150-year-old farmhouse is not simple.
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| This old, rotted sill will need replacement ... there's nothing left of it. |
Should the damage be very minor – limited, let’s say, to the outer inch or so of a heavy timber sill – you may be able to cut away the rot and splice in a new face piece made from pressure-treated material. This is something most of us can accomplish without a lot of special tools or know-how.
But when the damage is more extensive, the process quickly gets complicated. Temporary structural bracing and heavy jacks will be needed to stabilize the house while you’re working on it.
This is not the best place for on-the-job training. Unless you know what you’re doing, you’re better off calling a professional. He or she will have the right tools and the experience to get the job done without getting hurt and without doing any more damage to your house.
Just as important as fixing the damage you find is taking steps to prevent rot when you rebuild your deck.
Adequate flashing where the house and the deck meet is a crucial first step, and that’s a topic worthy of its own column. I’ll tackle it next time.
