Vinyl siding over drywall?

[kurt]

I've searched the VSI and this site for the answer and can't find anything; I need some help.

This mornings job had vinyl siding installed over gypsum/drywall sheathing. The bsmt. was entirely finished except the furnace & electrical closets; in those rooms, I was able to lift the fiberglass insulation & could see the drywall sheathing. It was dry, there is housewrap (tyvek), and it seems OK, but drywall sheating????

Anyone ever heard of this or seen it?

[hausdok]

Hi Kurt,

Yeah, I see it done on newer condos out here all the time.

It's usually part of a layered wall system wherein the drywall is placed behind the OSB, the whole thing is wrapped and then the siding goes on. I've never bothered to ask why. I always assumed it was some kind of firewall engineering. They typically use an exterior grade drywall, and, unless the flashings at penetrations has been done poorly, it seems to work fine. Sometimes I find it flipped the other way with the drywall on the outside of the lamina. In fact, I believe that the the building I'm living in is done exactly that way.

There are a whole lot of little 1,000 sq. ft. post WWII houses around here that were built for GI's after the war that are sheathed with an exterior-grade drywall that has a black paper facing. In most cases, it's held up for more than 50 years and still going strong. Of course, those aren't sided with vinyl though.

How many of you knew that drywall has been around for just about 105 years now?

ONE TEAM - ONE FIGHT!!!

Mike

[kurt]

OK. Thanks. I'm not a new house guy; some of this stuff is weird.

[fqp25]

I've recently seen some Exterior Grade Gypsum Board that is 7/16 inch thick; I guess they are to cheap to give them a 1/2 inch of sheathing, of any kind.

[paul burrell]

I seldom if ever see building wrap under vinyl siding in my area. I wonder if this is a local thing or is included in 2006 IRC? I have 2003 and 2000 IRC but not 2006 IRC. My area uses 2000 IRC with local up dates. I am going to research this item but someone out there may know the answer.

Thanks,

Paul B.

[Scottpat]

The exterior drywall that I have seen is not white in color, the gypsum has a cream to tan color. Also the paper backing is tan in color and can have what looks like fiberglass threads/fibers in it.

[kurt]

Further research......

It's part of the FRRA. The house setback was minimal, and they got a variance based on having an adequate fire resistance rated assembly.

Thanks all. And yes, this was a strange color; kinda grey.

[Scottpat]

Wait till you see a home with EIFS, and exterior drywall for a substrate!

[Brian G]

"Exterior drywall"....

If that isn't an oxymoron, it should be. What a stupid, stupid, stupid idea.

Brian G.

Endlessly Amazed & Dumbfounded [:-boggled

[randynavarro]

I'be been seeing exterior gyp on buildings (commercial) for years. I guess its just a west coast thing.

Since I don't do commercial stuff, I really couldn't explain the benefits of using it on the exterior. But I've seen it growing up, and all around cities just driving by and taking a gander at how stuff is built.

Have never seen it yet on a residence (except for multi-family).

[hausdok]

Hi,

This should be enlightening. click here.

OT - OF!!!

M.

[hausdok]

Hi Kurt,

Here's the stuff I've been seeing around here. Click here

ONE TEAM - ONE FIGHT!!!

Mike

[kurt]

Interesting.

I remember Fine Homebuilding ran an article many years ago about an architect in California that fought the muni's & won regarding gyp as a structural panel. Seems the critical consideration was glue; nailed panels didn't provide much (loosened up over time), but glued panels provided as much racking resistance as plywood.

I know it really stiffens up a frame when you glue 5/8" Type X to the walls & ceilings.

[Eric B]

This is new construction. Garage outside wall is built solely of wood studs, drywall and vinyl siding. No plywood, no OSB and no paper. I could't tell what the rest of the house was - for some reason they used housewrap.

[cguffin]

I seldom if ever see building wrap under vinyl siding in my area. I wonder if this is a local thing or is included in 2006 IRC? I have 2003 and 2000 IRC but not 2006 IRC. My area uses 2000 IRC with local up dates. I am going to research this item but someone out there may know the answer.

Thanks,

Paul B.

R703.2 Water-resistive barrier. One layer of No.15 asphalt felt, free from holes and breaks, complying with ASTM D 226 for Type 1 felt or other approved water-resistive barrier shall be applied over studs or sheathing of all exterior walls. Such felt or material shall be applied horizontally, with the upper layer lapped over the lower layer not less than 2 inches (51mm). Where joints occur, felt shall be lapped not less than 6 inches (152mm). The felt or other approved material shall be continuous to the top of walls and terminated at penetrations and building appendages in a manner to meet the requirements of the exterior wall envelope as described in Section R703.1.

Exception:Omission of the water-resistive barrier is permitted in the following situations:

1. In detached accessory buildings.

2. Under exterior wall finish materials as permitted in Table R703.4.

3. Under paperbacked stucco lath when the paper backing is an approved weather-resistive sheathing paper.

According to Table R703.4 in the 2006 IRC a Water-Resistant Barrier is required under Vinyl siding.

Thanks for the opportunity.

Craig

[Scottpat]

It might be required in the Code but the manufacturers that I'm aware of do not require it.

[Jim Katen]

Originally posted by cguffin

[br

R703.2 Water-resistive barrier. One layer of No.15 asphalt felt, free from holes and breaks, complying with ASTM D 226 for Type 1 felt or other approved water-resistive barrier shall be applied over studs or sheathing of all exterior walls. Such felt or material shall be applied horizontally, with the upper layer lapped over the lower layer not less than 2 inches (51mm). Where joints occur, felt shall be lapped not less than 6 inches (152mm). The felt or other approved material shall be continuous to the top of walls and terminated at penetrations and building appendages in a manner to meet the requirements of the exterior wall envelope as described in Section R703.1.

Exception:Omission of the water-resistive barrier is permitted in the following situations:

1. In detached accessory buildings.

2. Under exterior wall finish materials as permitted in Table R703.4.

3. Under paperbacked stucco lath when the paper backing is an approved weather-resistive sheathing paper.

According to Table R703.4 in the 2006 IRC a Water-Resistant Barrier is required under Vinyl siding.

Thanks for the opportunity.

Craig

Well, it's about time. That's a nice change from the 03 ed. How about wood siding? I don't suppose that you can scan that table and post it?

- Jim Katen, Oregon

[cguffin]

Jim,

I do not have the capability to scan this from home. According to the Table though water-resistive barrier is required on all siding material. There are a couple of exceptions with stipulations for the Fiber Cement Panel and lap siding. If I get the chance I will scan the table.

Thanks for the opportunity.

Craig

[cguffin]

Here is a list that require weather-resistant according to the table.

Horizontal aluminum w/insulation wo/insulation.

Brick veneer / Concrete masonry veneer.

note: For masonry veneer, a weather-resistive sheathing paper is not required over a sheathing that performs as a weather-resistive barrier when a 1-inch air space is provided between the veneer and the sheathing. When the 1-inch space is filled with morter, a weather-resistive sheathing paper is required over studs or sheathing.

Hardboard / Panel siding-vertical

Hardboard / Lap siding-horizontal

Steel

Stone veneer

Particleboard panels

Plywood panel / exterior grade

Vinyl siding

Wood rustic, drop / A weather resistive membrane shall be installed weatherboard fashion under the vertical siding unless the siding boards are lapped or battens are used.

Shiplap

Bevel

Butt tip

Fiber cement panel / lap siding: R703.2, Protection against condesation in the exterior wall assembly shall be provided in accordance with Chapter 11 of this code.

Craig

[Bob White]

It's a little clunky, but here's the table:

Download Attachment: table.pdf

91.72 KB