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iteach4jeeps 11-30-2012 05:17 PM

R3 Rigid Foam for sheathing??
First time home buyer here. Been living in it for over a year now. A burb south of DC in NOVA near Quantico. I noticed some mold on the uninsulated wall of my attached garage and it prompted investigating.

That wall is sheathed in this really cheap like particle board that is dark, almost like what you would find on the back of cheap 70's shelving units. Really easily breakable and not really water resistant since there is mold in a bunch of places. The rest of the walls are sheathed in R3 rigid foam with vinyl siding on top. This is the whole house except the vinyl covered chimneys and the attic which is the same weird particle board.

Is this right? I figure I am in a high wind area since my previous roof had many missing shingles. Is this within code or did my builder cut corners? No seams are taped, there is a 1/4 gap between each board where it is nailed to the studs. Inside of that is pink insulation then drywall. This seems really weird to me after seeing area homes being built in my area with actual plywood sheathing with house wrap.

Any input would be great!

brockmiera 11-30-2012 05:35 PM

Can you post some pictures?

joecaption 11-30-2012 05:44 PM

May be Celotex, one of the horrible ideas, right up there with partical board.

Have not seen that used in modern constrution in many years.
They were suppost to use plywood in all the outside corners.
Foam and Celotex has about 0 shear strength so you can expect some nail pops and funky noises when the wind blows due to the house moving.

iteach4jeeps 11-30-2012 06:09 PM

It looks like some of the celotex in the link. Is this something that would need to be replaced with plywood in the future?

I can't post pics since I'd have to pull some more vinyl siding.

The house definitely creaks in high winds, bangs a lot, vinyl I'm assuming.

Is the foam sheathing normal? I am 100% certain it's sheathed in foam.

iteach4jeeps 11-30-2012 06:12 PM

In the attic for sure, there is not plywood in any corners at all, it is 100% celotex or whatever that crap is. Not only is it up, it has random holes throughout like someone had a leak hunt and took a hammer or their fist to random places to find a leak. The vent cover is covering the most foul looking hammer busted up hole, I am not sure why they felt this was necessary and couldn't cut it out like normal people.

joecaption 11-30-2012 06:13 PM

Normal? I've seen it done years ago. I know I would never have used it.

iteach4jeeps 11-30-2012 06:25 PM

Yeah using foam as sheathing just looks and feels completely cheap. With home prices rising, I cannot believe I paid for a foam covered house. It seems ridiculous, its not even taped.

I wonder if anyone locally can chime in because I read somewhere that it was used in certain geographical areas due to climate. We get milder winters and pretty hot summers but it has gotten pretty cold.

I also wonder about the ability to keep out insects and other unwanted biological thingamajiggers with just foam laying over the bottom 2x4 plate.

Our home builder is still building homes in this area and I am thinking of giving them a call to find out what the heck they were thinking.

joecaption 11-30-2012 07:00 PM

We had one poster that said his new house in Hawaii was done with James Hardee siding with just foam under it.
Last one I saw we had to cut out a window anyway do make it into a door way and I showed the house owner to get in the house all I had to do was kick the wall.

woodworkbykirk 11-30-2012 09:13 PM

ive built several large high end homes that were sheathed in foam with no plywood on most walls. only the tall walls and shear walls were sheathed.. its common place now for most new homes and renos to get foam over top of the wood sheathing for added r-value and to act as a thermal break

you said there is 1/4 gaps in the foam. do they atleast have house wrap over the foam. if not your looking at a major risk of air leakage and water getting in which will increase both the heating bill and the chance of rot and mold

cleveman 11-30-2012 09:41 PM

I've built 3 homes with 1" t&g xps as sheathing, but there was metal diagonal bracing in place. They also got a brick veneer with a lot of ties into the studs. I don't know if any studies have been done showing that the wall ties in the framing/brickwork improve the structure, but I don't think it can harm anything.

I've always been hesitant to build anything like this and then just side it with vinyl because of only nailing 16" oc. But I recently sided a large garage which had the black asphalt impregnated sheathing (celotex) and I was just nailing into the studs every 16" and it seemed to work out ok.

So if I have the opportunity in the future, I wouldn't hesitate to brace a garage well, then sheath it with xps and side it with vinyl.

iteach4jeeps 12-01-2012 11:56 AM

There is no house wrap and no tape on the seams. It is frigid in the winter but we try to keep the heat on 72 at the max. It seems very drafty in this house. When you pull outlet covers, you can actually feel wind blowing through.

woodworkbykirk 12-01-2012 12:16 PM

the gaps in the foam is the issue then its not stopping cold air from blowing into the wall cavity and taking any warmth from the insulation. if the outside walls are bare do yourself a favor and install house wrap

as for the metal t braces that get installed.. ive done this their only good if the brace is more than 7 `long and run on a 45 degree angle from the bottom plate to end stud.. in a wall thats full of glass the framing is really chopped up so bracing is useless it really needs sheathing before the foam

iteach4jeeps 12-01-2012 02:44 PM

Am I going to have issues with moisture with a house wrap? I have no exposed walls but it could be a project for me this summer. I can take down a wall of vinyl siding and wrap it, then put the siding back up.

iteach4jeeps 12-01-2012 02:45 PM

Is there any other way to fill in the gaps in the foam? Expanding foam, tape or any other product I do not know about. Trying to research every avenue so I might not have to wrap.

Gary in WA 12-01-2012 03:19 PM

Contact your local AHJ, ask them about shear wall requirements in a high-wind area; charts 1/2 way down (looks like you live in a 90):

This would apply for your shear wall panel requirements per location: eg.-

Bracing with metal struts- minimal resistance:

If you add structural panels:

Size of fastener, fastener spacing, stud spacing, per MPH wind Zone, Chart 603.3(3);

Read the first 3 on (code required) water resistance and WR barriers, also the last one on vinyl siding/foamboard;

Foamboard shrinks, breaking any air-sealing joint tape connection;


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