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Mobile home ceiling saging

arrowshooter | Posted in Construction Techniques on March 31, 2002 06:48am

I framed over the existing roof on a mobile home adding a one foot overhang and osb + felt +shingles also laid in 6 inch insulation over the existing metal roof of the trailer. Now , after about a year  The ceilings inside are showing water stains and the ceilings are bowing downard. The wood system itself is not sagging just seems like moisture is condensing out above the ceiling and being absorbed by the celotex type ceiling causing it to bow downward. The tenants have been using kerosene heaters rather than the vented gas furnace provided but the problem didn’t start until after we added the new roof.

If you have any thoughts or suggestions about this problem please reply.


Edited 3/30/2002 11:49:57 PM ET by ARROWSHOOTER

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  1. Piffin | Mar 31, 2002 12:18pm | #1

    Kill the renters to put them out of their misery before they choke on the carbon monoxide, fix the gas furnace so the next renters can use it, and open the windows to let it dry out.

    This would be a great Q for "Click and Clack talk houses"

    You may have made it harder for vapour to escape by adding the superstructure at the same time that they were adding more vapour inside from the exhaust.

    Excellence is its own reward!
    1. arrowshooter | Mar 31, 2002 03:17pm | #2

      What is a "click and clack talk house" ?

      The furnace does not need "fixing" it runs on LP gas and I supply a 250 gal tank

      but I can't force the people to buy gas for it so some of them use these stupid kerosine space heaters to try and save money. Home Depot sells these things along with cans and funnels and hand pumps so stupid people will buy them. These tenants had moved out before I found the problem.

      1. JamesDuHamel | Mar 31, 2002 04:51pm | #3

        You have a leak(s) somewhere. The 6" insulation may very well be trapping moisture, and an opening somewhere in the existing mobile home roof may be letting the moisture in. But... somwhere you have a leak or two or three...

        Please tell me that your NEW roof is actually built OVER the mobile home roof, and has its own support. If the new roof was built directly on top of the existing mobile home roof, and the mobile home's old roof is actually supporting the weight, you are gonna have some serious problems. James DuHamel

        1. arrowshooter | Apr 01, 2002 05:21am | #7

          Thanks James and all others for the reply. I've been roofing over these things for years  and have had no problems with  the roof structure. We just put double 2x4 top plates down each side and use 2x4 trusses on two ft centers with OSB and standard shingles. We are about 20 miles North of Atlanta and hardly ever get snow but we have had as much as five inches with no problems. I think the problem is being caused by the kerosene heaters. Metal roofing is the rage around here now so we have done some of these by striping the trusses with 1x4s on two ft centers and screwing the roof panels down. The metal comes in all colors and is 3 ft wide and costs about $150 per Ft cut to length. The homes are single wide by the way.

          1. JamesDuHamel | Apr 01, 2002 06:11am | #8

            Sounds like ya got everything under control.

            I've been REPAIRING these things for years, and it never ceases to amaze me how little most common people know about the engineering of a mobile home. These things are designed, engineered, and built as a unit. They are made to flex, and are made to have some give. I've seen permanent type repairs that prevent the home from ever being moved without completely destroying the new work. I've also seen repairs that would make a mute man scream due to shoddy work, lack of knowledge about how to do it right, and just plain ignorance. You do not sound like you fit any of these types of people. Good for you.

            I deal directly with a lot of mobile home manufacturer's Engineers and Designers. The more I deal with them, the more fascinated I am about how these things are designed and built.

            In my area, we get NO snow at all. Weight of the new roof is what causes so much failure here for existing structures. Mobile home walls and roof supports cannot take ANY extra weight. They were not designed to, nor will they hold up. Metal roofing is a different ballgame, although it does add some weight. Shingle roofs with new decking adds a considerable amount of weight. I have seen mobile home ceilings that were over my head, and two months later I couldn't walk through without ducking my head. The ceiling panels had sagged THAT much! Of course, the whole roof had sagged that much too!

            I said you'd most likely have a leak somewhere because the INSIDE of the ceiling panels are covered in pastic. A sort of vapor barrier you could say. It takes a LOT of water to get past this plastic seal and soak the fiber panels. The panels only start to sag after they get really wet. The weight of the water logged panels makes them sink and sag.

            I have seen an awful lot of mobile home owners use kerosene and other fuel fired space type heaters without any of the effets you are describing. Landlords here have a bad rep for not reparing the heaters and a/c units when they go out, so the tenant is left with whatever alternative they can afford.

            I feel your pain, and know your situation. Been there, done that, still doing it.James DuHamel

          2. PatchogPhil | Apr 01, 2002 06:30am | #10

            James

            I've seen some older (1960's) mobile homes that did not have any plastic in the ceilings.    If I remember correctly,  in around 1974 the "code" rules for mobile homes changed drastically.  Perhaps that's when plastic was added?

            Phil

          3. JamesDuHamel | Apr 01, 2002 08:17am | #11

            Patch,

            The oldest mobile home I have ever worked on was a 1957 Brentwood. Guy STILL lives in it, and it looks new. He keeps it very well maintained. It did have a plastic lining, but he also has replaced the ceiling panels. The new panels may very well have had the plastic on them when he installed them a few years back. I have run into some of the older ones that did not have the plastic barrier.

            The average mobile home I work on is probably early 90's, maybe late 80's. I do see a lot of mid 70's into mid 80's, but not a WHOLE lot. These older ones are usually owned by landlords who repair them themselves.

            The last one I repaired had severe roof damage because the previous roofer was ignorant of mobile home roofing designs. He treated the roof just like it was on a regular stick framed roof on any average house. This was a plywood decked, asphalt shingle roof on a double wide. He sent a crew of four up there, set the shingle bundles on the decking, and proceeded to work. Broke damn near every 2 x 2 truss in the roof. I ripped off the old roof decking, replaced the trusses with 2 x 4 trusses, and redecked and shingled the roof. Took lots of pictures too! The trusses ONLY touch the outer wall plates, with no load on the ceiling joists at all. I left the old truss joists in place because the ceiling panels were attached to them. This job was a mess, and a nightmare. Came out very well, though.

            James DuHamel

          4. Piffin | Apr 01, 2002 07:49pm | #12

            "Mobile home walls and roof supports cannot take ANY extra weight."

            Some clarification - As a general rule you are right and certainly in south Tehjas, but there are mobile home manufactureers that engineer roofs for higher loads. Those that sell in northern climates have to. For instance, In Grand County, Colorado, where I used to work, there were three load zones. Any residence needed engineering for 40#, 50#, or 70# live load because of snow in different areas. The mobiles in your area couldn't meet that so if you were moving into the county, you couldn't have a building permit to place it. You would have to build a shed roof, separately supported over the mobile home.

            Several manufactureres have responded to this need in the northern snow areas with stronger designs. I don't know how good they can do but I think some can get up to 45 or 50#.

            Excellence is its own reward!

          5. JeffOps | Apr 02, 2002 02:53am | #14

            C'mon, James, give with the pictures.

            : )

            Cloud has a great place you can upload them to, so that you don't have to take up your 'allotment' here...

            Whattaya mean, I can't be three people at once ???!!?

          6. PatchogPhil | Apr 01, 2002 06:25am | #9

            I agree the moisture problem must be solved.  And those kerosene heaters are dangerous.

            However,  I've seen quite a few older mobile homes and in 99% of them,  the interior "celotex" type ceiling panels sag and droop.  And the older models are pretty drafty (self venting).   Whatever the reasons,  you can remedy the ceilings.

            After you resolve the moisture issues you can use 1x3 or ripped plywood strips and fur out the existing ceiling going perpendicullar to the ceiling "joists" or ribbing.  You'll never get the ceiling plane level without losing a LOT of head room.  Then apply 3/8" drywall and tape and paint as usual.  Unless of course,  the roof trusses cannot support the drywall weight.   I've also seen grid-type drop ceilings done in mobile homes.  The sponge-like tiles work best since you can set the drop very close to the original ceiling.  The sponge-type allows bending of the tile without breaking.

            HTH

            Phil

      2. Piffin | Mar 31, 2002 07:41pm | #4

        http://cartalk.cars.com/Radio/Show/

        One of the most hilarious programs you've ever heard on talk radio. NPR

        Excellence is its own reward!

  2. HarleyJClark | Apr 01, 2002 01:49am | #5

    Sounds like what Piffin suggested with the vapour. Uphere in my part of Canada, CMHC wants the old metal roofing taken off or at least cut out so the condensation isn't trapped between the steel and asphalt roof; and wet the insulation.

    1. JamesDuHamel | Apr 01, 2002 05:10am | #6

      Who is CMHC?

      Are you saying that they advocate building a stick framed roof, covered in asphalt shingles directly ON TOP of mobile home wall/roof framing? Without separate and independent support?

      James DuHamel

      1. HarleyJClark | Apr 02, 2002 02:25am | #13

        Hey James, CMHC Canada Mortgage and Housing. Roof is framed just like Arrowhead said. Like you I do a bit of work on mobile homes. In Canada we just call them mini homes.What's the largest mobile homes do you guys have in Texas? Up here 16'x74' is the largest right now.The homes definetly have improved since the 70's and 80's.

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