insulating osb board underpinning

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william45
Posts: 8
Joined: Sun Jan 05, 2014 8:31 pm

Hello everyone my double wide has osb board around it for underpinning and was wondering if i should put foam board behind it for insulation in the winter time.

Thanks William
1987Commodore
Posts: 383
Joined: Mon Oct 25, 2010 9:53 pm
Location: Steuben County, NY

You can, but if the belly wrap is intact, it is not really necessary. I wouldn't put too much effort into the osb, as it will rot quickly if exposed to moisture, particularly ground contact.
william45
Posts: 8
Joined: Sun Jan 05, 2014 8:31 pm

Yea i know about the osb and rot had to replace it before.
I do need to do some work on the underbelly where i have made plumbing repairs.
Last year winter electric bills were very high. Was wondering if that will help some putting up insulation behind the osb board.

Thanks
bobfather99
Posts: 195
Joined: Fri Nov 13, 2009 2:09 am
Location: Indiana

Certainly wont hurt things insulating your skirting.
You can also check windows and doors and seal around them to keep out drafts.

Keep in mind also that in 2013-14 the northern part of the USA had one of the worst winters in the past 30 years, so utility bills would be much higher than the average winter.
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Greg
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It NEVER hurts to insulate the skirting. Mark is in S.Dakota and has insulated skirting, He claims that it has never gotten below freezing under his home.

Greg
"If I can't fix it, I can screw it up so bad no one else can either."
william45
Posts: 8
Joined: Sun Jan 05, 2014 8:31 pm

So what is the best way to attach the insulation to the osb board.

Thanks
jimncheryl
Posts: 52
Joined: Fri Dec 20, 2013 1:12 pm

I might be missing something here.
All of the OSB I have used is resistant to moisture damage. I found some 2x2 pieces in the dirt around our home , we bought this place 4 years ago, anyway the OSB is still good, made an
impression on me.
The sub floor is more like MDF or particleboard, it seems like one drop of water can do thousands of dollars in damage.
I had to replace a section of floor due a cracked plastic fitting in the wall and replaced it with 3/4
OSB and this is 2006 model home.
The material used on the sub floor should outlawed.
Jim
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Greg
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Location: Weedsport, NY

Jim, I hope you don't want an argument over Particle board, I don't think anyone here will give you one.

Greg
"If I can't fix it, I can screw it up so bad no one else can either."
jimncheryl
Posts: 52
Joined: Fri Dec 20, 2013 1:12 pm

Not about Particle board. The statement was made " OSB will rot quickly if exposed to moisture"
is far from a being correct and needs to be corrected. OSB is more durable than plywood.
Jim
ponch37300
Posts: 622
Joined: Tue Nov 11, 2008 6:12 pm
Location: wisconsin

OSB is not moisture resistant and will expand and weaken when exposed to the elements for a period of time. It is more durable then particle board(MDF) but isn't rated to be exposed. It can take some moisture and not completely fall apart. But a prolonged exposure and it will also be damaged.
jimncheryl
Posts: 52
Joined: Fri Dec 20, 2013 1:12 pm

Properties


OSB, closeup of corner.
Adjustments to the manufacturing process can impart differences in thickness, panel size, strength, and rigidity. OSB panels have no internal gaps or voids, and are water-resistant, although they do require additional membranes to achieve impermeability to water and are not recommended for exterior use. The finished product has properties similar to plywood, but is uniform and cheaper.[7] When tested to failure, OSB has a greater load-bearing capacity than milled wood panels.[8] It has replaced plywood in many environments, especially the North American structural panel market.
While OSB does not have a continuous grain like a natural wood, it does have an axis along which its strength is greatest. This can be seen by observing the alignment of the surface wood chips.
All wood-based structural use panels can be cut and installed with the same ease and types of equipment used with solid wood.
Some manufacturers treat the wood chips with various borate compounds which are toxic to termites, wood boring beetles, molds, and fungi, but not mammals in applied doses.
ponch37300
Posts: 622
Joined: Tue Nov 11, 2008 6:12 pm
Location: wisconsin

jimncheryl wrote:Properties


OSB, closeup of corner.
Adjustments to the manufacturing process can impart differences in thickness, panel size, strength, and rigidity. OSB panels have no internal gaps or voids, and are water-resistant, although they do require additional membranes to achieve impermeability to water and are not recommended for exterior use. The finished product has properties similar to plywood, but is uniform and cheaper.[7] When tested to failure, OSB has a greater load-bearing capacity than milled wood panels.[8] It has replaced plywood in many environments, especially the North American structural panel market.
While OSB does not have a continuous grain like a natural wood, it does have an axis along which its strength is greatest. This can be seen by observing the alignment of the surface wood chips.
All wood-based structural use panels can be cut and installed with the same ease and types of equipment used with solid wood.
Some manufacturers treat the wood chips with various borate compounds which are toxic to termites, wood boring beetles, molds, and fungi, but not mammals in applied doses.
I highlighted the important part in Red. They are water resistant, but there is a HUGE difference between water resistant and water proof. It also says OSB is not for exterior use and it requires an additional membranes to achieve impermeability to water.

Here is some more technical info from a website just for OSB, http://www.osb-info.org/technical.html.

"When components are factory produced for installation on site, it is essential that the site conditions are suitable to receive the components with wet trades completed and the building dried out.
OSB with enhanced moisture resistance (OSB/3; OSB/4) is not waterproof; the term ‘moisture resistant’ applies to the adhesive binder which (within limits defined by EN 300) will not break down in the presence of moisture. Physical wetting of all grades of OSB should be avoided."

So basically says the glue they use is water resistant, but even the 2 highest grades of OSB aren't made to get wet and shouldn't be used for outside. I've seen OSB that has been used for skirting and for outside projects and have seen it after a few years exposed to the elements and while it will hold up better then particle board it still swells and breaks down over time. It just isn't meant to be used on an exterior and be exposed to elements and I don't think you will find any company that will say it's alright to use exposed to the elements.
1987Commodore
Posts: 383
Joined: Mon Oct 25, 2010 9:53 pm
Location: Steuben County, NY

OK, how about I change my post to -- OSB will fall apart relatively quickly, due to the fact that the bottom edge will be exposed to constant moisture, being presumably in constant ground contact when used as skirting, and thereby having moisture wicking up into it from said ground contact. This will degrade the materials used, causing the board to flake apart, turning it, starting from the bottom, water impregnated edge, into a pile of mush, unless you have perfectly sealed the edges, or happen to live in a dry climate, with well drained sandy soil. Once the bottom edge has disintegrated enough that there is no longer direct contact with the earth, degradation will slow, but not completely stop, unless the osb is protected from moisture.
Grade 1 OSB will have a shorter service life than grade 4.

Better?
jimncheryl
Posts: 52
Joined: Fri Dec 20, 2013 1:12 pm

I do not see that anybody said OSB was water proof, none of the these posts make that statement.
Moisture resistant is a long way from water proof.

The statement OSB will rot quickly when exposed to moisture is simply incorrect.

That being said I would not use OSB for skirting around a mobile home, even here in Ca.

I have Hardy Panel as skirting, my home is 8 years old now and no problems.
When we built the garage, we used OSB for siding, it was marked which way it was to be installed
an arrow pointing up indicated the proper position, the bottom edge had a coating from the factory
for moisture control, and we installed hardy panel over top of it,not one problem,passed inspection easily.
ponch37300
Posts: 622
Joined: Tue Nov 11, 2008 6:12 pm
Location: wisconsin

I'm going to make one more post and then we can agree to disagree I guess. The word "quickly" can have different meanings in different environments. I have seen OSB deteriorate quickly. So to say that is false, is false.

The simple fact is OSB is NOT meant to be used where it will be exposed, period. It's not water proof, only the adhesive is water resistant. When used as a sheathing and then has a membrane such as hardi board or vinyl siding or whatever then it is fine. But left exposed to the elements it will deteriorate, how "quickly" would depend on a variety of things.

But no matter what it is not rated to be used on an exterior exposed to the elements. Even the article you quoted states that.
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