Roof leak - Qs about roof/ceiling construction

Steve-WA · Thu Mar 15, 2012 11:16 am

I am new to the board - can't believe I haven't found this before now. Been Lonnie Dealing and landlording MHs for over 10 years now.

1973 singlewide, metal/metal. Tenant complains roof leaks: I seal, and pull down ceiling, drain and remove vapor barrier and insulation in the affected area, replace insul only, did not replace plastic v.b., put up sheetrock. This happens a few times over the next several months.

In pulling down the ceiling, though the roof is sealed, there is water beading up like crazy on the underside of the metal roof - I am guessing it is condensation since I did not replace the plastic v.b. Also, I noticed that there is apparently ceiling panel material between the rafters and the metal, but all soaked and saggy. Is this just a type of padding between the metal and the wood, or is it added to insulate?

I have opened up the ceiling above the electric furnace, so that it draws some ventilation through the ceiling area. I added vents outside at the ends up high (had one, added two more per end), I also cut about 4 holes in the roof and screwed and tarred plastic vent caps (all of this progressively to eliminate the moisture.

I am about to just put on a metal siding roof like this site shows, but I don't want to if I dont have to. Short of that, my guess is to tear out previously repaired ceiling, replace insul as necessary, and put a vapor barrier back up. But what about that fibered material between the wood and the metal? Do I need something there?

Greg · Thu Mar 15, 2012 4:30 pm

Hi & welcome. So you have no vapor barrier? As long as you are sure there are no leaks, it must be a condensation problem. I am not sure what the formula for ventilation is but you may need more. I'm sure JD will add to this.

Greg

JD · Fri Mar 16, 2012 7:20 pm

I am guessing you are from Washington State with the WA in your user name. You definitely want the vapor barrier intact. That is what stops warm moist air from hitting the cold metal roof material. When this happens, it is just like a coke can sweating. The ideal way to install this vapor barrier is to attach it to the bottom of the trusses, which would mean removing ceiling panels. The material between the trusses and roof is there to protect the metal from wear and to enhance expansion and extraction. I would cut strips of 30# roof felt, slide it between the wood and the metal and staple it down to the sides of the trusses so it will stay in place. If you do use roof felt, you do not want total coverage, as this would be like a second vapor barrier. Just use strips attached to the top cord of the trusses.

Steve-WA · Tue Mar 20, 2012 11:13 am

Thanks for the info JD - the thing is, the original material (between joist and metal roof) is ceiling panel fiberboard, and about 3/4 inch thick. Will tarpaper be thick enough?

Crap - gotta rip it all out again. And with tenant in place. . . unless I wait for turnover! If it gets to be a problem again, I'll redo it right this time, even if they're there. Thanks again.

and yes, WA state. I find that with online communication, location is often relevant, so as often as possible, I use the Steve-WA handle.

Deb M · Wed May 02, 2012 2:22 pm

Hi, I am a new member.

A client called me to install spray foam on her underside of her metal roof on her mobile home. I inspected it and found that she had a leak, with her ceiling tiles (suspended ceiling) stained and moldy in one room. Looking up into the cavity, I saw that she had paper-faced FG batts (about 8 inches), and above the trusses was a metal roof with a poly sheet up against the underside of the corrugated metal roof. From the exterior, there is an area near the edge of the roof that coincides with the area where there was a leak that is damaged/breached. Her son used some flex seal spray they ordered from TV.... Of course that didn't stop the leak. This is located in NJ and I believe that the barrier/the poly sheeting shouldn't be against the metal roof and is causing condensation in addition to the leak.

I don't have a ton of experience with mobile homes but I do have training in energy efficiency and weatherization with these manufactured homes and as such, this scenario doesn't make the best sense.

I would most likely repair the area on the roof with a metal flashing or even peel and seal and then put an elastomeric sealant (2 coats) on top. Of course I will recommend the roof be cleaned first and I will be able to find any other leakage points and the repair will adhere better.

As for the poly sheeting right against the metal roof, is this a standard? I don't think so. I believe the poly should be below the insulation and the insulation in that case should not be faced. What is the best way to handle this?

Greg · Wed May 02, 2012 5:54 pm

Hi & welcome. About the only way to patch a metal roof is by screwing or riveting a metal patch over the hole and sealing it up.

As for the Spray foam, that is new enough that we really haven't much experience with it here. If anyone here has used it They haven't said anything. So with that in mind I hereby authorize you to be the OFFICIAL tester for the site!!!

Greg