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chronojosh 02-14-2013 08:16 AM

Vinyl Siding Over Wood, Double Vapor Barriers, and Windows..oh my
2 Attachment(s)
I have a 1 story ranch built in the late 1950's and I am planning on residing it in the next year or two depending on my budget. The house is board and batten siding with 3/4" tongue and groove board sheathing underneath and felt paper between the two. During my renovations, inside the 2x4 walls I installed R-15 kraft faced fiberglass with the kraft paper facing inside. I tuck taped all joints and air sealed all wire penetrations in the walls/floors/ceilings. I replaced all the windows with new construction vinyl windows and screwed the nailing flange to the outside of the board and batten siding (First Diagram). I plan on putting Tyvek on the outside of the house and integrating in into the window flanges to properly flash and seal the window from leaks. I then want to install 2" XPS and then my vinyl siding (Second Diagram). Is there any issues with with regards to this possibly being a double vapor barrier set up? Also, what housewrap should I use for this? Do I caulk all of the seams between the boards after I remove the battens to install the housewrap? I do plan on cleaning up the wood siding and adding a coat of good quality paint to protect the wood for the long term. Any issues with how I am going to do this? I don't want to pull off all the wood siding and have to remove all the windows I have installed, since this will effect my trim inside around the windows. Thanks.

chronojosh 02-14-2013 08:19 AM

Also, just FYI, the window flanges right now that are screwed to the outside of the house are caulked and I used peel and stick flashing over them.

joecaption 02-14-2013 08:52 AM

Got a picture of one of those windows on the outside?
I'm not a big fan of your plan of adding foam to the outside like that.
A double vaper barrer like that can as you suspect cause moisture issues in side the walls.
It will also cause possible water leaks around the widows and doors because there going to be sitting so far back.
What should have been done as a rule is add spacing to the old trim and sill, wraped the exposted wood with coil stock then install the window, then the sidiing.

chronojosh 02-15-2013 09:19 AM

3 Attachment(s)
I am unsure of what you mean about how it is more prone to leak this way once it is finished. The second and third attachments are close ups of how the peel and stick flashing is on the flanges. I paintes over it juer so it sort of blends until I finish the siding. So what should I do to integrate the windows and keep them from leaking once I do the siding? What is wrong with adding the extra xps insulation?

chronojosh 02-15-2013 09:21 AM

Also, what should have been wrapped in coil stock?

Gary in WA 02-16-2013 01:28 PM

Did you caulk the seams of the wood sheathing before adding the f.g. batts to air seal? Did you ADA the drywall when installing; to stop exfiltrating air? Or are you air-sealing the foamboard?
The paper facing is a vapor retarder, not barrier, allowing the wall to dry to the inside- if needed. The foamboard will keep the dew-point warm enough from condensing water vapor in the cavity/on the sheathing. The paper face will slow any moisture from diffusing outward, yet still allow drying to the interior. You will be alright with the make-up as posted, pp. 3;
Another discussion on vapor retarders/barriers;

Use a latex paint only on the inside/outside. Use Dupont "stucco-wrap" with the grooves to help drain any liquid water that makes it behind the taped/flashed horizontal joints, not the flat one. Will you be adding a pan flashing or similar to the window holes-- never-mind, It appears they are already done...Exterior foamboard flash details, pp 10;

The tape may come off, I would use an acoustical sealant between sheets and metal flashing at the horizontal joints;

Good with f.b. over the WRB (housewrap) for your location, pp. 5, 13;


chronojosh 02-16-2013 01:58 PM

So I should use the stucco wrap instead of regular tyvek? I was planning to air seal the foamboard seams. I haven't started taping and mudding yet, so is it too late to try and caulk at the drywall seams? Gary, do you think that my plan in diagram 2 is feasable and will keep my windows from leaking? Thanks

Gary in WA 02-16-2013 02:04 PM

I edited my earlier post...


Gary in WA 02-16-2013 02:27 PM

I think the caulk under the flanges is fine, the P&S will probably come loose when the wide wood board expands/contracts with the seasonal humidity changes, leave it, just be sure to run the H.W. over the flanges to help water out/down, except UNDER the bottom flange to facilitate drainage. Caulk the drywall seams, top, bottoms to prevent air leaks. Especially seal the 1/8" x 12" = 1-1/2" hole around all electrical outlet/switch boxes that allow 100 times more water vapor in a wall than diffusion,
Even caulk all the box holes, including the one the wires come through. Air exfiltrates through the plug holes when under heating pressures, though you shouldn't caulk

PS. I would use some metal flash at the head with end dams to prevent water from directing to the jambs;

joecaption 02-16-2013 02:48 PM

Gary take another look at the overhangs (or should I say lack of an overhang)
On the gable ends.
How do you expect to use 2" thick foam with no over hang?
The biggest issue I see is there's just no great way to trim out those windows with that thick a material. You can not just count on caulking to keep water out with the trim sticking out past the windows like that.

Also look at the lack of soffit vents.

chronojosh 02-16-2013 03:19 PM

Ah. Thanks. I was planning on adding the soffit vents when I did the siding. I was wondering about that overhang. I already had the roof replaced, is there a qay to add the overhang now?

joecaption 02-16-2013 03:31 PM

Nope, you would have to go back and remove the shingles all along the edges.

Does that fashia there now slope or is that just the picture?

chronojosh 02-16-2013 03:47 PM

If you mean the fascia coming down from the chimney, then yes it does slope down toward the overhang over that triple ganged window.

joecaption 02-16-2013 03:50 PM

Strange way to do it.
All I can picture is any water getting behind the gutters running down that slope and over the face of the siding.

chronojosh 02-16-2013 04:20 PM

2 Attachment(s)
Maybe these pictures will help

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