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Window Flashing Question.


Terence McCann
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I see this all the time, and have even taken the battle to local code enforcement. They buy into the builder's pitch that the windows are "self flashing," due to the nailing fins. I don't know about other areas, but around here, I can't imagine any builder admitting a mistake was made and then removing and reinstalling the finish materials to flash the windows.

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Originally posted by Bain

I see this all the time, and have even taken the battle to local code enforcement. They buy into the builder's pitch that the windows are "self flashing," due to the nailing fins. I don't know about other areas, but around here, I can't imagine any builder admitting a mistake was made and then removing and reinstalling the finish materials to flash the windows.

This is the answer I received from the manufacturer's rep of Pella windows.

The builder applies a special strip of material, similar to anti-ice material for roofing, to the nailing fins. You can then install the finish exterior siding over this waterproofing material.

I gave the name and number of the manufacturer's rep to my client and suggested they call him to stop by and look at the installation. If he still thinks it's ok have him put it in writing on his letterhead.

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The few different brands of windows I've ever installed do not specify metal head flashing. They simply specify ice-shield and/or wrapping the sills and jambs much like Pella describedyou've described from Pella.

Here is the Standard Practice for Installation of Windows With a Mounting Flange. http://www.milgard.com/_doc/products/aama-2400-02.pdf

Those instructions are posted on the Milgard website - it is how they specify their windows to be installed. Don't know about other parts of the country but Milgard is probably one of the most popular and higher quality window mfg. on the west coast.

They do not specify metal head flashing. They use the term 'head flashing' to describe the ice-shield or building paper wrap under the siding. See Page 2 - Note 1 - they say it is not the responsibility of the window mfg. to design or recommend an appropriate flashing system.

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I installed some Pella clad casement windows on our addition last year. I just dug out the installation instructions.

Their flashing instructions are called "Integrating the window to the water resistive barrier". In other words, installing flashing tape. The final instruction is "Sealing the window to the exterior wall cladding". For wood siding and trim, they specify a 3/8" gap, backer rod and sealant.

Maybe I should have read the instructions before installing them. I need to go out now and tear off the head flashing.

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Hi,

I rarely see head flashings in new construction here anymore, unless it is on high-end homes or where there is a pretty savvy builder involved. When I do see it on other-than-high-end homes, they usually install the head flashings over any windows on the street-exposed side of the house or on the south and west (weather) sides.

The standard here is to slap some Moistop or a similar material across the bottom of the rough opening, nail the flanged window home, add a couple vertical pieces at the side and then overlap the top flange with the building paper without installing any of the self-adhering stuff across the top of the window. Then they side the house and caulk the hell out of the perimeter. For the most part, it works most of the time but when it goes bad it goes really bad.

I write up the lack of head flashings on 99.999% of the houses I do. I know there's not a whole lot one can do about it - especially if it's a 35 or 30 year old house with aluminum windows that have never leaked - I just want customers to understand that they were, and still are, the standard when it comes to a quality install, and that for many decades windows were installed without any self-adhesive material using ordinary felt splines and head flashings and those walls remained dry, as opposed to thousands of installs today that leak.

Then I point out that upper end and intelligent builders are still incorporating them into their installs here, but that manufacturers, for the most part, aren't requiring them anymore, and that they (the customer) will need to ensure that they have every weather-exposed window carefully inspected and the caulking touched up annually.

Like the lack of drip edge flashing that I write up on most homes, most folks pooh, pooh it. No skin off my a**, if they leak later on I certainly won't be the one that didn't warn them about the potential Achilles heel hiding behind their siding.

ONE TEAM - ONE FIGHT!!!

Mike

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Originally posted by hausdok

Hi Terry,

You say it's "wood" siding. Wood as in plywood attached over a layer of wood sheathing or wood siding attached directly to the studs with a layer of building paper behind it?

OT - OF!!!

M.

Hello Mike:

Wood siding connected to the studs. There were only small sections of this on the home. The area as shown in front of the house and the kitchen area behind the home. The rest of the home, with the exception of a little stone, was vinyl siding.

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Alllllrighty then!

Take a look at page 41 at this link for clapboard and shingle siding (Notice the splining behind the drip cap and head flashings? (Hmmmmmm?)

http://www.awc.org/pdf/WCD1-300.pdf

Then look at the details for plywood siding at this link:

http://www.apawood.org/pdfs/download_pd ... d/A530.pdf (If you haven't already, you need to register here.)

ONE TEAM - ONE FIGHT!!!

Mike

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  • 1 year later...

I'm gonna dredge this up from the distant past....

Image Insert:

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Image Insert:

2007712114729_windows_non_flashed.jpg

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All the windows at the plywood sided portion of the rear of this home are unflashed (see top photo) while all the rest of the windows installed where there is lap siding have observable head flashing.

The windows installed over plywood have only a small bead of caulk and a coat of paint to prevent water intrusion.

I'm gonna get a battle from Pulte on this one, because every home in the subd. is built this way.

So -- Do they need to flash these windows? Is caulk enough?

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  • 1 month later...

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