PLYWOOD UNDERBELLY

Repair help for the do-it-yourselfer.
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Cajun One
Posts: 11
Joined: Mon May 09, 2016 6:57 pm
Location: Manteno IL

I just closed on my first mobile home a 1972 12X65 single wide which is in very good shape for its age,on the 24th of June, which was empty for a year it was winterized when the owner moved. It's total electric with baseboard heat. I looked under the home to see the condition of the underbelly, the manger of the park had said the owner had it reinsulatted a few years back. I noticed between the main I beams it has plywood on top of the beams with 1X4 covering the seams and on the outside of the main beams has the black board stapled to the bottom of trailer with outriggers every 2 foot. So my question is does this sounds like a good job because the plywood is sitting on top of the main beams with 1x4 covering the seams. I dont know if the insulation has been compressed because the fact of the plywood is above the beams. I would like to add a half bath to the master bedroom if possible and a washer and dryer closet in the rear of the home. It's sitting on blocks on the ground there is no footings below the frost line which was code back then, which now has changed to a foundation wall has to be poured below frost line for any new home that is brought into the park. What do you guys and gals think would be the first step of action is the take out a piece of the plywood to see how it was done :?: :?: :?: :?:
Mark440
Posts: 279
Joined: Tue Feb 26, 2008 8:33 am
Location: Anna, Tx

I'm going to take a guess that when he had it re-insulated, the insulation was stapled to the bottoms of the floor joists, then the plywood installed - possibly nailed or screwed to the same. The furring strips are there probably just to seal up the seams between sheets of plywood.

I would think it would be somewhat easier to remove the plywood sheets necessary to accommodate the mods, and then put them back. Personally, I am over repairing/patching/messing with that belly fabric. (...and one of these days.....me and a utility blade.... :mrgreen: )
Opportunity has a shelf life.
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Greg
Moderator
Posts: 5696
Joined: Wed Feb 28, 2007 8:01 pm
Location: Weedsport, NY

Personally I would shy away from totally sealing the space like that, You need ventilation. If you (when) you have a plumbing leak or just plane condensation the moisture needs someplace to go or you will have a mold issue. the space needs to be able to breathe.

Greg
"If I can't fix it, I can screw it up so bad no one else can either."
Mark440
Posts: 279
Joined: Tue Feb 26, 2008 8:33 am
Location: Anna, Tx

But here's the part i just don't get. Back when the belly was intact - I got a water link at en elbow leading up to the kitchen sink. of course, I didn't know I had a leak until I started getting that funky-moldy-stale smell up in the house. I went under, and that belly material was a big ol' pool liner. No visible leakage - just it had stretched as was hanging way, way down.

I don't know how deep the water was inside the belly. But when I did a 2-3ft slit in the belly, the water gushed out in a solid stream for several minutes. All of the insulation across the span of 8-10 floor joists was soaked, but the water had not got up as high as the bottom of the joists themselves.

The part i don't get is if that fabric is supposed to "breathe" and let moisture out - how the heck does it hold that much water?

I'm not asking to be controversial.....I just need to understand as I need to replace my belly as well. I looked at plywood and also some sheets of plastic that could be screwed, stapled to the bottom of the floor joists.
Opportunity has a shelf life.
yakima4$
Posts: 83
Joined: Tue Oct 20, 2015 11:02 pm

The belly skin installed under the homes is both a vapor barrier and pressure envelope and a way to support the blown in or batt insulation.
It stops air from migrating into the home belly of the home and up into the walls. Plus moisture from the ground warping the floor decking. It is not a breather paper like type R nor any paper/house wrap that is installed under siding.
You should though by code install black 6 mil plastic on the ground.
The man with the plywood belly, I would not touch that plywood until after the first winter and see what the power bill is. The floor is constructed to what is called a SIMS panel construction and is probably more energy efficient than any other mobile home out there.
This hanging the insulation down in the belly skin is nothing more than a MFG saving money on construction of the home. How many Plant managers or production managers of MFG homes live in the product they produce. Only one I know of and he was with Fleetwood in Indiana. And his plant built a IRC modular not a MFG home for him.
Any way your can get the insulation up in substantial contact with the floor you are far ahead.
I inspect for compliance with IRC,IBC,NEC, HUD,UPC,IMC,ARMA codes and all types of modular structures.
I have traveled with HUD nation wide to inspect MFG housing plants, which pertained to auditing there quality control program and verifying the knowledge of the inspectors. I have been and still am a inspector with over 30 years experience (last of the Mohicans). So I have some back ground in what I speak to.
But I do not become involved with all issues on this web site for days are short and so are allot of folks on money,.
I will through out a idea that is code compliant and let folks do what they want.
Mark440
Posts: 279
Joined: Tue Feb 26, 2008 8:33 am
Location: Anna, Tx

yakima - I couldn't find anything for SIMS panel construction - but I did find SIPS panels. So i am hoping they are the same thing.

And thank you for your experience and insight on this. My interest in replacing the plastic belly material has more to do with a better physical barrier than the insulating aspects. I live in Texas, so it doesn't get below zero hardly ever. But, I live out in the country, and blocking the critters is a never ending challenge. I've had several instances where they just chewed right through the plastic skirting. And once they gain access, the damage is endless.

You've given me some great ideas. Thanks!
Opportunity has a shelf life.
yakima4$
Posts: 83
Joined: Tue Oct 20, 2015 11:02 pm

I meant SIPS.
Yes those critters love a place to hide and nest.
If you do replace the belly skin you will want to seal all penetrations of the floor decking with foam or caulk and seal off around tub drains with plastic (staple up around the perimeter of the of the deck opening at shoe location). Sealing these penetrations stops the air from migrating up inside the walls. I am assuming your house does not have the gray poly water piping that had the recall years ago. If it does you will want to replace that along the way. Depending on the year home was built you may also want to tape/or use a mud/paste sealant at the metal duct transitions.
This will be a job and you may want to hire folks to help.

Ron
yakima4$
Posts: 83
Joined: Tue Oct 20, 2015 11:02 pm

Second thought.
If the idea is to stop vermin and yours eat through the plastic skirting.
Install concrete runner under skirting and replace plastic skirting with metal.
Allot less work.
Also periodically through rodent bait under home fall and winter.
I lived in a triple wide and the mice would get in the walls and start chewing the studs. Why I don't know, but you could here them at night at one location.
I had a pit set with concrete foundation. Once I started on a schedule of rodent bait under the house it took about two years but problem was resolved.
You have some tough rodents in Texas.

Ron
Mark440
Posts: 279
Joined: Tue Feb 26, 2008 8:33 am
Location: Anna, Tx

"Install concrete runner under skirting and replace plastic skirting with metal.
Allot less work."

That's where I got to as well.
Opportunity has a shelf life.
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