How To Flash A Window Opening
Given the fact that windows create large holes in a house's exterior, I'grand always shocked to encounter how many builders in our area don't install them correctly. In the nine years that I've been building and renovating homes, I've seen windows that haven't been integrated with the housewrap, improperly flashed installations, and even windows with no flashing at all. Not only does improper installation affect the durability and warranty of the windows, but it also exposes the wall crenel to moisture problems.
Like any builders, my crew and I want to use efficient practices that won't negatively affect the quality of our work. For usa, that means using a businesslike approach to installing windows with worst-case scenarios and long-term durability in listen.
Water Gets Behind All Siding, So Window Flashing Is The Next Line Of Defense
Based on conversations with subcontractors and local edifice officials, we've concluded that the reasons windows aren't installed correctly frequently stem from an unrealistic expectation about the effectiveness of siding in keeping moisture out of the wall cavity. What many window installers don't realize is that no matter how well siding is installed, moisture finds its way between it and the housewrap.
When wet ends up on a layer as slick every bit housewrap, it does a logical thing: Information technology slides down the wall. One time that moisture reaches the window, it easily finds its way into the rough opening through even the tiniest holes. Moisture that leaks into a wall cavity causes mold to abound. Mold is bad, for materials and for humans. That's why we do everything we tin to continue water moving out and away from the window past integrating it with the housewrap.
Read The Window Manufacturer's Installation Guidelines
Most window manufacturers recognize the disastrous issue improper installation of their products can have on a dwelling, including pregnant energy loss. That'south why they provide detailed installation instructions for their products. Post-obit these instructions helps to continue the wall cavity dry and fulfills the window manufacturer's warranty.
Although the photos show my crew installing metal-clad windows with integral flanges, the steps outlined here offer a await at cardinal elements found in most manufacturers' installation guidelines. They address forming the waterproof sill pan, shimming the window so that it works properly, and flashing the flanges to shed h2o. These steps will receive LEED points every bit well.
We figure that our sillpan and flashing approach adds nearly 10 minutes to the installation fourth dimension for each window and an average of $15 in materials for each double-hung unit. That's relatively inexpensive insurance for such a large investment.
What To Do When Guidelines Conflict
These days, every housewrap, flashing-tape, and window manufacturer has a specific fix of installation guidelines that must exist followed to uphold each respective production's warranty. So what do yous do when they contradict one another?
We follow contributing editor Mike Guertin's advice and use the most-restrictive protocol. For instance, when the window manufacturer shows no flashing details, nosotros follow the tape or housewrap instructions. When one set of instructions calls for a unproblematic flat sill pan and another calls for a sloped pan, create a sloped pan. It'south unlikely someone will merits you didn't follow the instructions by doing more than than is called for.
When in doubt, though, follow the window manufacturer's instructions. The International Residential Code (R613.i) requires windows to be "installed and flashed according to manufacturers' instructions." If there's e'er a problem, you've done what was required by the building lawmaking.
Gear up The Rough Opening With Housewrap And Pan Flashing
Most builders brand an 10-cut in the housewrap and staple the resulting tabs into the opening prior to installing the window. But folding the peak tab into the opening gives h2o a manner in behind the window's top flange. Instead, cut a top tab that covers the window'south top flange afterward the window is installed. Then add pan flashing to collect and drain any h2o that does go in.
We brand our pan flashing on site with beveled siding and self-adhesive flashing tape using Typar'south 9-in. wide Flashing Flex to flash 2×6 walls because information technology allows us to form a seamless pan that contours to the sill. Other brands and widths are too available.
The Top Tab Folds Up, Not In
| Starting time, cut beyond the header, and so down the eye. | Make a horizontal cut and two angled cuts to the sill. |
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| Staple the tabs downwards, then cut the top tab. | Fold up the top tab, and tape it out of the way. |
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Site-Fabricated Pan Flashing
Beveled siding creates a sloped sill. After wrapping the opening, nosotros nail a piece of siding along the rough sill with 13⁄4-in. roofing nails. Be sure to add together the thickness of the siding to the window'due south acme when framing the rough opening. Self-adhesive flashing tape goes on adjacent. In cold conditions, nosotros apply spray adhesive (also called "primer") to improve the tape'due south adhesion. The Flashing Flex record we're using hither calls for 3M's Super 77 agglutinative. We run flashing tape tight to the within of the opening and 10 in. up each trimmer stud, so fold the residuum over the housewrap. We sometimes staple the corners of the tape to prevent them from moving.
Ready-Made Pan Flashing
For us, making sill pans on site is efficient and cost effective. Merely in that location are manufactured pan-flashing systems available, such as Dow'south Weathermate Sill Pan, shown here ( www.dow.com ; $v). This can be an economical pick if you don't take a lot of windows to install. They come in diverse sizes to fit the opening's width.
Caulk, Shim, And Boom The Window In Place
With the rough opening set, it'due south time to install the window. Almost manufacturers require the side and top flanges to be caulked to the perimeter of the rough opening. They illustrate adding the caulk to the flange, simply nosotros like to add it to the building instead so that it doesn't become all over our hands every bit we put the window in. Regardless, make sure there's a good seal effectually the flange. Get the window fully nailed off before the caulk dries.
Lap The Tape Shingle Style
Cocky-adhesive flashing tapes generally pause downwards into ii types: asphalt and butyl-based. Asphalt-based tape can damage certain types of vinyl, so cheque the window's specs before using information technology. Butyl tape is easier to piece of work with. It doesn't have an aggressive initial tack, but its adhesiveness increases over time. When possible, we employ tapes made by the manufacturer of the housewrap we're using considering the products are designed to piece of work together.
| Extra protection for the head jamb. The head jamb is the about-vulnerable part of the window, which is why these windows come with a drip cap that adds a layer of protection. A similar cap can be made with flashing record and aluminum coil stock. | The sides run long. Run flashing tape four in. to five in. past the height and lesser flanges. Make sure the tops of the side pieces stay at to the lowest degree 1 in. short of the tiptop of the head slice then that the head piece volition have a good, continuous bond with the sheathing. For windows with integral flanges, like the ones we're installing here, butt the record tight to the jamb. |
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Tape the top. Roll tape over the pinnacle flange, letting it run past the side pieces by 2 in. to 3 in. One time the elevation piece is in place, fold downward the housewrap tab. Tape along the bottom of the flap and at the corners with housewrap tape. Leave the bottom flange record-free. The window is now ready for casing and siding.
Mechanical Flanges Require Extra Attention
Not all flanged windows are made the same. The windows shown in this article accept an integral nailing flange, which means that the flange is part of the window'southward exterior cladding. Integral flanges are a good blueprint considering in that location aren't seams or joints for h2o to sneak by. Hinged (photograph, left)) and non-hinged (photo, right) mechanical flanges are also found on vinyl and metal-clad windows. Although these flange styles aren't inferior to integral flanges, they have a few vulnerable areas that require actress attending during installation. Mechanical flanges are sometimes too phone call practical flanges. — by Mike Guertin
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Mechanical flanges fit into grooves effectually the window jamb. They rely on a ribbed spline to stay engaged in the groove. The spline and a narrow gasket work together to keep out water. Hinge-fashion flanges are shipped folded confronting the frame, which leaves the corners incomplete. Manufacturers supply metal or plastic corner pieces to be applied and caulked once the window is hung. Non-hinged-style flanges overlap to class the flange corner. One benefit of mechanical flanges is that if they get damaged during installation, they are easy to replace. You lot install them by borer a woods cake forth the within tab. The downside is that they can become disengaged afterward installation for a variety of reasons (for instance, the siding installer pushes or bumps the jamb, or someone steps on the sill earlier it's shimmed in place).
To reduce the chance of window leaks, I make sure that everyone who works around them is aware of damage areas. I also shim effectually the window jamb's perimeter every half dozen in. and spiral through the jamb and shims into the framing. Finally, (ane.) I lap the flashing tape about 1⁄4 in. onto the side jambs and then over the flange and housewrap. At the window caput, (ii.) I run the tape over the jamb and down onto the window face by ane⁄8 in. to 1⁄4 in. I so install metal cap flashing over the caput-flashing record (3.) to conceal the tape.
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More than on Windows:
Drip Cap Design and Installation – The lowly drip cap needs to be taken more than seriously to forestall leaks and rot.
Flashing for Former Windows – How do you lot go a practiced weathertight seal on old windows that don't accept a flange?
Leak-complimentary Windows Serial: Sill Pan Flashing Options –Pre-formed or site-congenital, pan flashing channels water out where it won't rot the sills under windows or the floors nether doors.
Watertight window flashing – Q: When installing new windows, I believe it is considered good do to allow the head flashing above the window trim to overhang a trivial scrap on each side. This …
Window Flashing – A collection of manufactures on window flashing.
Window-Opening Preparation – Protecting the rough opening helps with air-sealing and water management.
Source: https://www.finehomebuilding.com/project-guides/windows-doors/installing-and-flashing-windows-correctly
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