Tyvek Under Foamboard?

laffingboy

I was told that if I put up 1/2" foamboard under vinyl siding that I don't need to use Tyvek under the foamboard because the board acts as a vapor barrier.I live and work in the Buffalo NY area and 2x4 exterior walls have become prevalant with the architects in the area. So in order to get the desired R value I need to use foamboard. Thanx

Grumpy

In our area TYvek is a requirement. Insulation is an option. When we install siding we put the insulation first then tyvek over the insulation.

hatchet

It'll also depend on what foamboard you purchase. Some of it has a type of vapor barrier - they will also sell tape for the butt joints. Personally I would do what Grumpy suggested and purchase non-faced board with taped Tyvek seams.

__________________
Rich
WIT Construction Co.
Superior MT Contractor

Unregistered

in nj we use 1/2 or 3/4 inch dow board t/g but i always use 15 lb felt if your going over raw plywood but not ness. but on old work its just ridged board as a leveler

Grumpy

We typically use 1/4? because the 1/2 or 3/4 makes the house look weird. Everything that is supposed to stand out like window sills looks sucked in.

I hate to admit we don't tape as often as we should because they customers dont usuallyw ant to pay for the upgrade. That tape is expensive... but if it was my house I'd make sure it's taped.

Unregistered

i agree with the sucked in on the sills we generally put 2 peaces of lath on the sill and the foam right over the legs with the j on top of that

Sawdust

Interesting....
I never use Tyvek over the board but I do tape the joints. And as far as windows, the sunken look has forced me to double-up the legs, head and sill with 1x. Even if the customer doesn't care it just maintains the character of whatever structure your working on (not to mention it would make me nuts as I drove by in the future.)

Grumpy

The problem I have is customers don't want to pay to build out the window sills or moldings. I'm gonna charge at least $50 per window to do that.

I just did a house with 32 windows. I charged $60 per window to cap, add $50 to that and were talking a a few thousand bucks more!

J2Jonner

Grumpy, What do you usually do when confronted with those "mobile home" type windows? The one's that are only an aluminum frame with a shallow 1/4 integrated J? I'm residing a 20 sq split level with these and the homeowner is happy with the windows, and the existing masonite siding is butted tight into the integrated J. I bid the job without insulation board, which would have been nice to level out the walls soley because I cannot see a good way to fur out the windows. Current plan is to caulk the existing aluminum J to the masonite, then but the vinyl J up to it and caulk the joint. Thanks!

6stringmason

I do masonry and I can tell you I HATE foam board! I would like to know why its better than OSB on the outside of a house. One contractor I do work for uses 1" and doesnt tape the seems. Well when you have a 4" brick ledge and the bottom plate already hangs over the foundation by an 1", yes an inch, and you add a 1" piece of blue crap to that, well, that doesnt really leave much of a workable brick ledge. Anyway I would like to know is it better to have foamboard than say some 3/4" osb tyveked and insulated? Just so I can try to dissuade the contractor to do it to the parts that are at least going to get bricked.

J2Jonner

The main factor as noted above is the insulation factor. People need to achive certain R values in many parts of the county these days, and in an effort to retain a 2x4 exterior insulate outside of the wall cavity. It also insulates over the wall stud, increasing the overall effective R value. That's my take on it anyway. I don't do new const., and if I did, it would be OSB with foam over it. I would take into account your brick of coarse thought!

bergenbldr

Why would a framer overhang plate 1"??? we set ours back 1/2 so its flush after sheathing.As for the vapor barrier issue only foil faced is actualy a barrier. We only use this in basements on inside walls.Tyvek is highly vapor permeable similarly to 15lb felt.

6stringmason

I dont know why they would overhang it an 1" but they did. Around half the house the left it over. I wish I would have taken pictures to show you. I feel sorry for the people who bought this house. The gc wanted to hurry up and get it done for the showcase and built the half million dollar home in something like 80 days. You were lucky if you could find one square corner. This guy is one of those who doesnt do ANY work he subs everything out.

bergenbldr

Must be one of those to good to use a tapemeasure framers.Ever heard about oldtimers using stick rule to layout walls.666666666 ft+23inches.

Scott736

Builders use foamboard when the cost of osb goes up... I'm a sider and foamboard sucks..

Grumpy

Wait a minute here. You can't use foam board in lieu of some type of backer board. Foam board has no sheer strength. It has no strength what so ever. It's just a big sheet of styrofoam!