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-   -   wall sheathing, foam board, insulation and house wrap (http://www.diychatroom.com/f19/wall-sheathing-foam-board-insulation-house-wrap-4113/)

dr.demento 09-28-2006 04:29 AM

wall sheathing, foam board, insulation and house wrap
 
I am resiiding my entire house and removing the existing siding. There is no sheathing or insulation under the siding. I am replacing rotted sills and studs, windows, and insultation as I have the walls exposed.

My original plan was:

1) install R-15 insulation in the walls from the outside as I have the walls open.

2) Cover with 3/8" plywood (realized that 1/2" or OSB would have been better.

3) Install new windows (has old wood windows). Used windowwrap flashing around windows.

4) cover the sheathing with tyvek housewrap

5) install the siding.


Questions I have about foam board:

1) would it be wise to also use foam board? I do not want to use just foam board as a sheathing will give the walls strength.

2) If I use foam board to add R value, what order should I install? Sheating, foam board, tvyek wrap? If I use foam board, do I even need tyvek wrap?

3) Would I install the windows last or after the plywood?


I have already installed the fiber glass insulation and covered with plywood on one side. I have also installed a few windows there. Is it too late to add the foam board? If not, would I use the house wrap next or the foam board?

I live on the gulf coast (se texas), the house was built in 1943. Any input would greatly be appreciated.

I do my own work very well when references and documentation is available but I have not been about to find much for the various tasks I am engaged in! :)

Big Dave 09-28-2006 06:41 AM

Around my area they use the osb for the corners only and then foam board to fill in the remaining area. Some builders will osb the entire wall but it usually amounts to cost effectiveness. If you are going to house wrap make sure there is no plastic on the inside walls. The house wrap is basically to stop air movement which is a good thing. The windows are installed after the osb or foam board and tyvek but before siding. 1/2" thick material is what should be used for your outside sheathing as all windows and doors are sized for this thickness of wall. Anything thinner will let the doors and windows protrude farther into the house making it harder to trim.

Hope this helps, Dave.

edit: The thinner wall sheathing makes no difference though if you are using windows that have to have a jamb made and installed later but it still affects the doors.

Sportbilly 09-29-2006 05:29 PM

And make sure you lap the tyvek the right way with the windows, it should be on the outside of the flange at the top, and inside of the side and bottom flanges.

stuccoman 09-29-2006 07:55 PM

I thought the wrap went under the fin on the bottom and over it on the sides and top. To properly kick the water out.

dr.demento 09-30-2006 12:54 AM

the wall depth probaly wont be a problem. the inside has some 5/8" tongue and grove wood covering all the walls. another question, would it have been acceptable to just use the foamboard instead of the plywood at all? just curious...

Big Dave 09-30-2006 07:09 AM

Like I stated above you at least need the osb on the corners to add stability to the structure. As for the tyvek, it should be wrapped around the framed opening before installation of window. Then after installing window use an approved sealing tape around the window.

Sportbilly 10-03-2006 05:55 PM

Quote:

Originally Posted by stuccoman (Post 19582)
I thought the wrap went under the fin on the bottom and over it on the sides and top. To properly kick the water out.

Yes sir, that's what I meant about the top, may have phrased it badly, the sides seem to vary depending on where one reads it.

Some manufacturers say not to tape the bottom fin, btw, for water egress

BLKMGK 10-05-2006 09:26 PM

Some siding can be gotten with a styrofoam under layment. The stuff on my house is backed with this stuff. Adds some backing to the foam and insulation as well. what I didn't do was wrap it before the foam with Tyvek, I won't make that mistake twice!

frank nichols 10-18-2007 04:18 PM

I am working on an old house. The old siding has been removed exposing tar paper under which is one by material. The owner wants to put 1 inch pink foam over that, than the new siding. Questions. If you put pink over tar paper does the tar paper degrade the foam? Does the placing of foamboard lead to a barrier for moisture from the inside of the house to condense and drip down to the bottom plate eventually rotting that out. Would you use furring strips on the top of the foamboard to mount the siding on or just nail through the foamboard. Where if anywhere would you use Tyvek Thank you Frank

Cole 10-18-2007 04:25 PM

Frank, what kind of siding are you going to install?

Vinyl, Fiber Cement, Wood Etc?

frank nichols 10-18-2007 04:42 PM

siding
 
I know this will be unusual but my friend has a large pile of 1/2 inch by 6 inch Douglas fir. We understand that this is unusual and has all sorts of ramifications , such as cupping, but there are budget problems and it will work for a few years till he can do better thanks


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