# Tyvek as mobile home underbelly?



## lenaitch (Feb 10, 2014)

What type of "repair" are you trying to do with these materials? Tyvek is a typically a house wrap that will pass water vapour (both ways) but block liquid water. It can be damaged by cutting or other abrasion fairly easily. I don't know how it would fare with critters and I don't know how it would fare under a structure but it doesn't last when exposed to sunlight. Roxul is insulation and not really a repair for anything.


Both are intended to be covered by something.


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## Nealtw (Jun 22, 2017)

That is a strange choice, roxul or tyvek??


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## CodeMatters (Aug 16, 2017)

Suggest posting pic(s) of the area needing patching.


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## mark sr (Jun 13, 2017)

I've always just stapled roofing felt to the underside of the floor joists. When there is plumbing lines run below the joists you can either build a chase or just float the felt over them .... don't forget to insulate those pipes.


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## ClarenceBauer (Mar 4, 2005)

http://www.dupont.com/products-and-...l-packaging/articles/seaming-and-sealing.html

Check put this article.


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## Thomas Kleaton (Mar 11, 2016)

Okay, I took some photographs yesterday afternoon which will probably explain better than I can describe. The photos showing what looks like fishnet is the underbelly resting directly beneath the ac duct work, and during the summer condensation drips from these areas constantly. At the other end of the house, particularly where the water heater was (I moved it when I installed a new one) and beneath where the interior ac/gas furnace was, the underbelly is missing completely. We had a new Comfortmaker heat pump installed outside four years ago with insulated flexible duct running to the original sheet metal duct work. 


I am looking for a way to insulate this sheet metal ductwork with something I can buy at Home Depot (roll fiberglass duct insulation?) and a way to cut out and add new material at these underbelly worn spots. I am also wondering if installing roll fiberglass insulation under the floor on the underbelly is the way to re-insulate these worn spots.


I plan on replacing all of the CPVC running to this bathroom with new thicker CPVC (whoever replaced the original Polybutylene piping used thinwall CPVC) and wrapping all pipes with foam insulation.


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## APA (Jul 13, 2018)

That looks like an older mobile home. What model is it? Does it have the underbelly wrap that feels like tar paper? The newer homes have a plastic type under belly that is really easy to patch. They even make patch panels. I have used spray adhesive and 6mil plastic, but either way it is a chore under there and it will never be perfect.


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## APA (Jul 13, 2018)

I have just gutted entire sections and stapled 6mil plastic to the rim joists between the frame with insulation glued to the plastic.sections. It is a single or doublewide?


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## Thomas Kleaton (Mar 11, 2016)

It is a 1983 Wicks doublewide. Not plastic underbelly, more like nylon fabric, although plastic underbelly material may work for patching, along with spray adhesive and/or underbelly tape. I'm thinking about just slitting the material along the duct run (water pipes also run through here) and patching it after replacing the water piping.


I want to insulate the ac duct run while I am at it, but wonder if I'll be able to reach the top side of the duct from the crawl space. The ducts are a few inches below the subfloor. I had one guy (who does this kind of work) tell me the ducts could be insulated by wrapping plastic around them and spraying inside the plastic with canned Great Stuff foam. I'm not a contractor, but from what I've read, this won't work.


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## mark sr (Jun 13, 2017)

I doubt insulating the very top of the duct would be worth the effort. Heat that escapes there will just warm the floor.


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## danomac (Sep 2, 2010)

I wouldn't use any type of house wrap, the wrap that specifically says it is for mobile/manufactured home underbelly use is both breathable AND treated so pests don't like to eat it.


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