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Vinyl Siding


DonTx
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I was just reviewing the vinyl siding guide for an upcomming inspection I have.

It appears from the illustration that on New Construction there does not have to be any house wrap. It shows the Vinyl installed directly over the OSB or Plywood.

Is this how vinyl is typically installed? It looks like any leaks would rot the substrate.

Donald

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Originally posted by Donald Lawson

It shows the Vinyl installed directly over the OSB or Plywood.

That design would be as fundamentally flawed as EIFS with no drainage plane if you ask me. Wind-driven rain, minor installation flaws at the detailed areas, or any kind of minor damage will result in water penetration. I wouldn't be comfortable with that sort of installation, no matter what the manufacturer said. Dumb is dumb.

Whatever the extra cost for installing the housewrap or other weather barrier, it's well worth it for all involved.

Brian G.

You Gotta Be Kidding Me [:-irked]

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Originally posted by Donald Lawson

I was just reviewing the vinyl siding guide for an upcomming inspection I have.

It appears from the illustration that on New Construction there does not have to be any house wrap. It shows the Vinyl installed directly over the OSB or Plywood.

Is this how vinyl is typically installed? It looks like any leaks would rot the substrate.

Donald

What guide where you reading? Every one I've seen requires a weather resistant barrier under the vinyl when used on new construction.

Even perfectly installed vinyl allows lots of water entry. The cool thing about vinyl, though, is that it also allows that water to dry out rapidly. (Unlike EIFS.)

Without a weather barrier, it'll make a mess though.

- Jim Katen, Oregon

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The guide I was looking at is the Vinyl Guide mentioned above.

My bad. Instead of reading the instructions, I was just looking at the illustrations. On page 13, it shows vinyl siding directly over the substrate. If I'd read the directions above the illustration, it would have told me to put a weather barrier on top of the substrate.

Vinyl is not used a lot here. Usually we find it on cheap mobile homes and homes of people who've fell victim to high pressure siding salesmen.

Donald

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Originally posted by Donald Lawson

My bad. Instead of reading the instructions, I was just looking at the illustrations. On page 13, it shows vinyl siding directly over the substrate. If I'd read the directions above the illustration, it would have told me to put a weather barrier on top of the substrate.

Well hell, it's not your fault then. Don't those knotheads know that men only look at the pictures when putting something together? No fair!

Brian G.

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Donald,

We have lots of vinyl here and I've installed my share of it along with the aluminum stuff...a long time ago.

So here is 1.5 cents worth if you want.

A weather barrier is paramount and mandatory in all siding application regardless of material. If you suspect it's missing, look under the corners as they are hollow and you can get a good view of the sheathing and the barrier.

The next thing I notice is the eveness of the installation. Is the siding 'relaxed' or has it been nailed to prevent expansion and contracion? If you suspect something is amiss, try moving the siding back and forth by inserting an awl or finishing nail into the drainage holes (every other lap). You shouldn't have to force a 12' piece to move it. If you study a length you'll notice notches at both ends, those are the overlaps and a movement of 3/8"-1/2" per 12' is normal.

Something else to watch out for, restricting the natural movement of the material, not to mention a possible water entry point.

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I could write all day but those are the big ones, the macro view.

The micro view will deal with details, that I wouldn't spend the time to memorize. I would simply ask the question "Will this keep water out of the structure?" If you're not comfortalbe then I'd default to the instructions.

I find applicators seldom follow textbooks anyway.

Good Luck with your inspection.

BTW vinyl has become expensive here, we also use it for fencing, decking, and railings.

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I just received this email from another inspector who saw the post and responded. What's your thoughts on his email?

Moisture barriers should be installed on the inside of the sheathing in

colder climates. It makes sense when you consider where the condensation is

likely to form.

In the South, the moisture barrier goes on the outside of the sheathing

since the warm humid air is usually (almost always) on the outside of the

house.

Up North, it's usually cold outside and relatively warm inside. If the

moisture barrier goes on the outside of the sheathing you can expect

condensate to collect on the inside of the sheathing, and then the moisture

is trapped right where you don't want it - in the sheathing and framing.

I'm not sure what the manufacturer recommends, but the effects of

condensation don't change depending on who makes the building materials! A

moisture barrier on the inside of the sheathing still meets the vinyl siding

recommendations. And I would certainly question any manufacturer that

recommends a moisture barrier on the outside of sheathing in a cold climate.

Will it make a huge difference if the barrier is on the outside of the OSB in a cold climate? What if you had one on the outside of the OSB and just behind the sheetrock?

Donald

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Hi,

He's confused and is mixing apples with oranges. He said, "The effects of condensation don't change depending on who makes the building materials." Well, he's right, but he is referring to vapor diffusion, not condensation. Condensation is a consequence of poorly controlled diffusion.

What he is referring to is a poly vapor barrier. Vapor barriers are used to slow/eliminate vapor diffision and prevent water vapor from condensing on the inside of the wall - either at the inner or outer plane - and accumulating enough moisture to foment rot. In cold climates they are placed just behind the drywall on the inside of the wall and in warm humid southern climates they are placed on the outside of the wall behind the sheathing. OSB has such a low perm rating that it is considered a vapor barrier by itself and the combination of poly used with OSB has resulted in some nice, moldy messes in some parts of the country. They don't use poly at all here, because putting it on either side of a wall would cause problems in our climate.

Your question, "What if you had one on the outside of the OSB and just behind the sheetrock," would result in a petrie dish where you could grow your own mold cultures for experiments. Don't ever do it.

Vapor barriers do not eliminate the need for a drainage plane behind the siding, which is what is being discussed here. Vinyl siding is essentially a rain screen. It allows wind-driven water to pass through and then drain down the backside and out through the weeps along the bottom. The moisture barrier simply protects the underlying sheathing from the direct onslaught of most of that water and allows the sheathing to dry out fairly rapidly once the rain stops. With vinyl you have to be careful to use something that won't bleed or react with the vinyl. Many installers use fanfold foam. Fanfold foam works well behind vinyl, because it can be installed in a drainage plane, goes up quick and doesn't bleed.

ONE TEAM - ONE FIGHT!!!

Mike

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The moisture barrier inside the wall. It creates a lose lose scenario. The moisture will condense on the barrier, run downhill and what doesn't get wicked back into the insulation will congregate at the sill. There's no chance of fresh ambient air to move the water out of the cavity and no incentive for it to go anywhere.

You also have the exterior of the sheeting totally exposed to the elements where it'll go through repeated wetting drying cycles. Osb will fail, and so will plywood.

Let's say you're roofing ..would you put felt under the decking?

Water vapor from inside the home infiltrating the wall is a serious problem and the interior of the wall should be well detailed to curtail it. The 1/8 gaps in the sheathing joints allow at least SOME exit for the water and once it's outside the sheathing it can be moved by gravity or air flow away from the structure.

I'm seeing quite a few new homes going up with a 1 inch hole in the sheathing drill every foot or so in a grid pattern. I think that's good idea. Time will tell.

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  • 1 year later...
Originally posted by hausdok

Hi,

"OSB has such a low perm rating that it is considered a vapor barrier by itself"

ONE TEAM - ONE FIGHT!!!

Mike

Does that mean this installation is possibly O.K. or is there a consensus that this is a bad situation?

The builder has been sued out of existence, and the potential buyer is getting a steal on a foreclosure. He may well have the siding pulled off and the house wrapped or felted if I recommend it, so I want to be right.

Thanks,

Tim

www.rqahomeinspections.com

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OK correct me if I am wrong but modern day house wraps although water repelent are gas permeable therfore allowing water vapor trapped in the wall to migrate out through the house wrap. As far as needing air to move moisture, seems to me moisture will want to equalize and does not require an incentive to move this proccess along.

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Hi,

I remember a few years ago where someone on one of the boards contacted the VSI or someone about that question and was told that it was okay. I personally don't think it is. The OSB functions like a vapor barrier but that doesn't mean that it is okay to repeatedly expose it to water. If you're guy is getting "a hell of a deal" than have him strip it off, islolate it from the OSB with a layer of building paper or some fanfols and reside it.

OT - OF!!!

M.

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From the 2003 IRC, in part:

Wall Covering

R703.1 General. (3rd sentence) The exterior wall envelope shall be designed and constructed in such a manner as to prevent the accumulation of water within the wall assembly by providing a water-resistive barrier behind the exterior veneer as required by section R703.2.

R703.2 Weather-resistant sheathing paper. Asphalt saturated felt free from holes and breaks, weighing not less than 14 lbs. per 100 square feet and complying with ASTM D 226 or other approved weather-resistant material shall be applied over studs or sheathing of all exterior walls as required by table R703.4.

It goes on to talk about horizontal application, 2 inch lap, etc.

But then lo and behold we go over to the table mentioned and it says sheathing paper is not required under vinyl. I think that gets changed in the 2006 IRC, to be required for all exterior wall sheathing, period.

With all of that said, it's nuts not to have a barrier under vinyl. Wind-driven rain will get behind vinyl even if it's installed perfectly, what's it like in the real world?

Brian G.

Vinyl - Having the Qualities of a Vine [:-paperba

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