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washisn
Joined: 11 May 2008
Posts: 1
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 Posted: Tue May 13, 2008 7:32 pm Post subject: moisture / thermal protection question |
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Hi all:
My question concerns with a typical masonry wall construction, is this:
When the Air/Vapor barrier comes to a termination (i.e. at window opening, roof, or foundation),
1. at the window head, does the A/V barrier overlap on top of the metal thru wall flashing or goes behind it? some sources I looked at (i.e. graphic standard) they have a layer behind, but a note saying "membrane flashing over metal flashing) Does it mean a third (extra) membrane flashing over the mtl flashing which is the thru wall flashing?? it is always drawn muggy at that junction. What is the typical/best practice?
2. At the roof, if I have a metal clad parapet, my strata is something like this, from the exterior: metal cladding-> 'membrane flashing'-> exterior grade plywood-> wood blocking and insulation-> a/v barrier->concrete block parapet structure. But I've seen construction drawings with the same note however, is reversed, "mtl flashing OVER membrane flashing"
As far as I'm concern, the air/vapor barrier has to go over and around the parapet, but again, some sources has it turned up and ended very muggy.
3. finally, at the foundation, where the water proofing membrane starts seems to be always at the i.e. edge of slab-on-grade, or edge of slab. Where should the a/v barrier turn and stop?
I'd greatly appreciate discussion/answers/comments. Thanks. |
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nanrehvasconez
Joined: 25 Feb 2008
Posts: 172
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| Posted: Fri Jun 27, 2008 6:17 pm Post subject: |
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1. Window flashing: FOR WOOD FRAMING: vynil and or aluminum windows have an nailing flange to set the window in the wood frame, Most building codes require that the exterior wall be sheathed with plyboard or SOB, strand oriented board, when the window is nailed to the wall, a 6" tar paper flashing strip is placed on top and sides of the window frame, no bottom strip is required, after that is compleated a Housewrap PVC fabric is installed over the whole building, prior to appliying the siding or the stucco finish.
2. Roof Parapet Flashing: flat roof connection between the parapet flashing and the roofing material has to be hot mopped with tar, if hot tar is not avalable the parpet flashing has to be nailed on top of a neoprene strip with a bid of caulking capable to seal the metal flahing and the final roofing material, if the roof is pitched, the parapet metal flasing should
be ample enough to avoid the water level to creep under the flashing system.
3. Foundation : the sill or bottom plate should be sealed against the concrete footing or slab floor, a bid of caulking is usually placed between the concrete and the wood. a 6" metal flashing with drip lip shall be nailed to the frame overlapping the foundation 2" below the concrete, the Housewrap Pvc fabric will be placed on top of the flashing.
Still water will creep via any litthe holes an became a problem. The graphic standards details are very useful, but an experience builder is boss. |
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