Date: Wed, 03 Jul 2002
Dear Dr. Rot
I hope you can help me with my problem. I recently built a carport that
was anchored to an existing slab floor. When I built the stud walls,
I failed to use a pressure treated or a redwood two by four for the
bottom base. The wood was not kiln dried, so there is some moisture
in the wood. And I'm afraid I will soon have dry rot in the two by four.
Is there any way I can treat that two by four where it is anchored in place to
prevent rot problems in the future? The walls are open, so I can get all
around them. I was thinking of drilling some small holes in the two by
four between the studs to help dry the wood .
When I set the walls up I put a strip of tar paper on the bottom
and up the sides so the two by four is encased on three sides with the
paper. What do you suggest ? Is there any place in my area where I can
buy the material you may recommend? Thank you.
First the easy part. We distribute our products only through mail order,
so we would ship them to you UPS.
Now on to your problem. First, I wouldn't drill any holes to dry the
wood out. It will dry out on it's own. Your situation is similar to what
people with decks face. The problem is keeping any additional moisture
from getting into the wood.
With decks, there are several main areas that commonly cause problems.
One is the nails that join the pieces of the deck together. The water
wicks between the nail and the wood, then soaks into the middle of the
wood and takes a long time to dry out. Another place is where two pieces
of wood touch, or as in your case, where the wood touches the slab. The
water wicks between the wood and the concrete, but when the rain stops
and the sun comes out, it can't dry out easily, giving the water more
time to soak into the wood. Lastly, we have end grain. Water absorbs
much easier into the end grain of wood than anywhere else. If you have a
place where end grain is touching something else, another piece of wood,
or concrete, look out.
In your case, you have a sill plate that is wrapped on the bottom and
sides with tar paper. I'm guessing that this is tacked/nailed in place
on the sides. As long as the tar paper lasts, this will protect fine
against ground flooding. If the sill plate gets any water hitting the
top of the wood, I think that the tar paper will actually make the wood
rot sooner. Instead of keeping the water away from the wood, the tar
paper is now holding the water against the wood. If the tar paper is
nailed down, the nail holes will help the water to get into the wood. So
unless water is never going to hit the top of the sill plate, I would
get rid of as much of the tar paper as is practical.
Then I would take some CPES and one of our injection kits, and
everywhere that the wood touches the concrete/tar paper, everywhere that
wood touches more wood, everywhere that there is a nail, I would use the
injection kit to shoot CPES into the cracks and wet the nails. Anywhere
that water is going to get in and sit. Start at one end, go to the other
end, then start again from the beginning and put on some more while the
first application is still wet. Wait a day, then put on another
application, this time only doing it once. I would probably wait a day
and do one more application, this time taking a cheap china bristle
brush and coating the whole sill plate, and as far up the studs as you
expect water to get to.
Once this cures, you will have a sill plate that has one coat of CPES on
the top and sides, and three coats at any cracks or nails. By having one
coat of CPES on the top and sides, rainwater will run off, but any
moisture that is in the wood already will still be able to come out. If,
over time, any cracks develop in the wood, I would take the injection
kit and put some CPES into the cracks to keep any water from getting
into the wood. This will protect the wood as well as if you had used
pressure treated wood, or better.
Let me know if you have any further questions.