Find the Cause of a Sagging Roof
LESLIE: Now we’re talking to David in California who has some problems with the manufactured home he’s living in. Tell us what’s going on.
DAVID: Well, I have a 1980 manufactured home and I have about a 10-foot by four-foot section of the roof that’s sagging.
TOM: Is it a pitched roof or is it a flat roof?
DAVID: Well, it’s a – it’s got a little angle to it.
TOM: OK, so it’s sort of a low slope.
TOM: Well, the first question I would have is why is it sagging. Is there any chance that there’s been a leak there?
DAVID: It doesn’t appear to be.
TOM: We want to eliminate the obvious, which would be, you know, a leak that could be weakening the structure. If you have no leak, this may be a situation where you have to do a little bit of exploratory surgery; perhaps in the area that’s the worse. I would work on this from the inside so we’re dealing with drywall and not roofing membrane. But you might want to open it up in an area and just make sure the condition of the lumber is solid.
If the lumber is solid and there’s no water, there’s no moisture, there’s no mold growing in there in this humid space …
LESLIE: Then it could be that one of the rafters is rotting.
TOM: Yeah, or more than one is what I’m thinking. Well, I would do some exploratory surgery here and try to find out what’s going on. If it turns out that they seem to be solid, they’re just sagging, then I wouldn’t worry about it so much. But if it turns out that you’ve got humidity and moisture in there, which is what I think Leslie and I are both suspecting is going on, then you’re going to have to do some major repairs. You’ll probably have to open that up from the bottom. You’ll probably have to sister each rafter by putting a new beam next to it.
LESLIE: Yeah, I was going to say.
TOM: And then you’re going to have to make sure you have proper ventilation because it’s the only way you’re going to keep it from happening again.
LESLIE: In addition to sistering the rafters, would you want to put a sort of beam perpendicular in between the rafters to just sort of join them together more than might already be there?
TOM: You talking about blocking?
LESLIE: Yeah, maybe.
TOM: Possibly, but I’d have to know more about the roof before I decided to do that or not. I mean you’re not going to put a midspan girder in unless it called for that, but you could put solid blocking, which tends to stiffen it up. The repair’s going to really depend on how much damage there is and how much area you have to work. But really, you need to open this up and figure out what’s going on, David. It does sound like something to be concerned about. So, you know, take it in small steps. Open up the ceiling from the drywall below – drywall’s easy to fix – and you’ll know exactly what’s going on. OK?
DAVID: OK. Thank you.
TOM: You’re welcome. Thanks so much for calling us at 888-MONEY-PIT.