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Reinforce a Rotting Box Beam

  • Transcript

    LESLIE: Listening in on WSVA, we’ve got Brenda in Virginia talking about a foundation. What can we do for you?

    BRENDA: Yes, I have a problem with water that’s coming off of my patio into my foundation right above the – it’s at the big beam.

    TOM: OK.

    BRENDA: Rotting up the beam that my house is – you know, part of the foundation; right above the foundation.

    TOM: Right. OK, that’s called the box beam, Brenda.

    BRENDA: OK, whatever it is. (chuckling)

    TOM: (chuckling) Alright.

    LESLIE: (chuckling) So, do you see that it’s rotting out? Are you seeing water on the interior? How do you know what’s going on here?

    BRENDA: Well, I see from the outside that it is rotting.

    TOM: OK. And so this is where – what is attaching to the house at that exact spot?

    BRENDA: The – it’s like T11 siding or whatever.

    TOM: OK. So what’s happening is the water is getting underneath the siding and then it’s decaying the box beam. Now is it the siding itself that’s rotting or is it the beam?

    BRENDA: Both.

    TOM: How do you know the beam is rotting? Do you – can you inspect it from the underside?

    BRENDA: Yes, you can hit it and see that it’s rotting.

    TOM: OK. Well …

    LESLIE: So you can poke a screwdriver right through it.

    BRENDA: Yes.

    TOM: Right. What’s going to have to happen here, Brenda, is you’re going to have to do some surgery on the wall. Now if you have T1-11 siding that’s the plywood siding with the grooves in it that looks like a vertical clapboard kind of thing.

    LESLIE: Like almost like a paneling.

    TOM: Yeah, like a paneling, right. What you’re going to have to do is remove the sheets of that paneling. Now, of course you could, you know, cut part of it off and then you’d have to put in a piece of S (ph) flashing where you rejoined it. Probably the best thing to do is to remove the siding. And then you can assess the condition of the box beam and you can cut it out and slip a new one back in. That work should probably be done from the outside but there might be another option and that is, if you can simply replace the siding and leave the rotted beam in place, you may be able to add a sister beam to the back side of it from – is this on a crawlspace or a basement?

    BRENDA: Crawlspace.

    TOM: OK, so you may be able to work into the crawl space and insert a sister beam next to it. Because since that box joist is only an inch-and-a-half wide and it’s going to be sitting upon a three-and-a-half-inch sill plate, you could put another box joist right next to it and, in fact, sister those two together. Try to find an area where you have some solid mass left in the original beam and then bolt them. And that’s one way to carry the load.


    TOM: But in either case you’re going to have to replace the siding and deal with the leak or it’ll just continue to repeat itself.

    BRENDA: Right. OK. I appreciate that.

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