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-   -   Window flashing question (http://www.diychatroom.com/f19/window-flashing-question-181901/)

markharmon 06-15-2013 07:51 PM

Window flashing question
 
Hi guys,

I have a question. Sometimes I guess two different answer from people I talk to so I figured I would ask here. When installing a new construction window and you plan on having a rigid foam or fanfold insulation should the window be installed before or after the foam? My thinking is that you want to incorporate the flashing with the house wrap, therefore, the window would have to be installed before the foam but then some people are saying they would install the window after the foam insulation. What do you think?

woodworkbykirk 06-15-2013 11:21 PM

you keep asking this question and we keep giving the same answer. install the window on top of the foam.. otherwise you will have to install a trim detail so the siding has something to butt up to.

for the flashing if i you put house wrap on top of the foam, just flash the window normally and have the house wrap lap over the flashing

markharmon 06-15-2013 11:50 PM

Quote:

Originally Posted by woodworkbykirk (Post 1201881)
you keep asking this question and we keep giving the same answer. install the window on top of the foam.. otherwise you will have to install a trim detail so the siding has something to butt up to.

for the flashing if i you put house wrap on top of the foam, just flash the window normally and have the house wrap lap over the flashing

Shouldn't the house wrap be attached directly to the sheathing?

Fix'n it 06-16-2013 09:53 AM

if you are using XPS, is house wrap even needed ?

Windows on Wash 06-16-2013 10:23 AM

It is cheap insurance Fix'n it.

And it should go over the XPS.

Pittsville 06-16-2013 11:18 AM

The WRB should be installed on the same plane as the window flanges.

http://www2.dupont.com/Tyvek_Weather...h_Bulletin.pdf

Video: http://youtu.be/d9XCwC-RuTk

markharmon 06-16-2013 12:49 PM

Quote:

Originally Posted by Pittsville (Post 1202089)
The WRB should be installed on the same plane as the window flanges.

http://www2.dupont.com/Tyvek_Weather...h_Bulletin.pdf

Video: http://youtu.be/d9XCwC-RuTk

Would you just staple the house wrap to the foam or cap nails?

Pittsville 06-16-2013 12:56 PM

Quote:

Originally Posted by markharmon

Would you just staple the house wrap to the foam or cap nails?

Cap nails for sure.

Windows on Wash 06-16-2013 01:48 PM

Quote:

Originally Posted by Pittsville (Post 1202134)
Cap nails for sure.

+1

make sure they are long enough to get through the foam and into the studs/sheathing.

There is debate over whether you wrap the WRB into the opening vs leave it over the top of the flange but that is for a longer conversation.

Gary in WA 06-16-2013 10:39 PM

Drainage plane under the foamboard on both "innie" and "outie" windows; http://www.buildingscienceconsulting...se_Studies.pdf

Just be sure to add shims/slope at sill first; Fig.9; http://www.buildingscience.com/docum...d-wall-systems

Where are you located? What type of siding? Any rainscreen? What brand of housewrap? Any poly vapor barrier under the drywall?

Gary

Windows on Wash 06-17-2013 08:06 AM

Quote:

Originally Posted by Gary in WA (Post 1202393)
Drainage plane under the foamboard on both "innie" and "outie" windows; http://www.buildingscienceconsulting...se_Studies.pdf

Just be sure to add shims/slope at sill first; Fig.9; http://www.buildingscience.com/docum...d-wall-systems

Where are you located? What type of siding? Any rainscreen? What brand of housewrap? Any poly vapor barrier under the drywall?

Gary

We would all love to have the budget that the BSC does when doing their wall details.

Most folks will not have the adhered layers at the sheathing plane in these type of retrofits.

markharmon 06-17-2013 07:37 PM

Quote:

Originally Posted by Windows on Wash (Post 1202516)
We would all love to have the budget that the BSC does when doing their wall details.

Most folks will not have the adhered layers at the sheathing plane in these type of retrofits.

So, if you do have some type of foam insulation then you can install right over the sheathing then housewrap then make the cutout for the window then install your flashing tape on the sill and over the flanges? Doing an innie window would be installing the window on same plane as the sheathing and your foam would be installed over the window flanges? If you did that then I would think you need some type of aluminum trim on the insides.

Clutchcargo 06-17-2013 08:32 PM

Rather than install the windows on top of the foam, why not add an extra layer of sheathing (maybe 4" wide pieces) around the window opening and then butt the foam board up to that. That would give you something more solid to nail the windows to.

Windows on Wash 06-18-2013 07:53 AM

Quote:

Originally Posted by Clutchcargo (Post 1202923)
Rather than install the windows on top of the foam, why not add an extra layer of sheathing (maybe 4" wide pieces) around the window opening and then butt the foam board up to that. That would give you something more solid to nail the windows to.

We usually do build SIP bucks around the windows for just that reason.

woodworkbykirk 06-18-2013 04:20 PM

Quote:

Originally Posted by Clutchcargo (Post 1202923)
Rather than install the windows on top of the foam, why not add an extra layer of sheathing (maybe 4" wide pieces) around the window opening and then butt the foam board up to that. That would give you something more solid to nail the windows to.


by doing that you lose the thermal break between the framing and the window unit.. . you simply go to a longer siding nail and use hurrican straps when installing the window


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