How To Install Blueskin Window Flashing

Kohta Ueno and Alex Lukachko demonstrate the proper technique for intalling a window and flashing in a rough opening during wall construction. And of course no flashing tape on a building wall, say over a window, is going to be able to prevent leaks that run down behind the housewrap from some leak point higher on the building. Question: Blueskin SA compatable for a tie-in with a 2-ply hot asphalt vapour retarder.

  • POST a QUESTION or COMMENT about how to buy & apply peel and stick flashing tape around window & doors or at housewrap joints or holes.

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Peel and stick flashing tape or membrane:

This article describes the selection and installation of peel-and-stick flashing membranes used on building exteriors to seal housewrap joints and to seal against air or water leaks around windows, doors, or other openings.

Our photo at page top shows Typar® flashing tape installed above a new window. A better practice laps the housewrap over rather than under the stick-on flashing tape, a better detail but one omitted by many builders.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Using Building Flashing Membranes - Peel & Stick Flashing Tape

How to buy & use flashing tape or peel and stick housewrap tape to prevent water leakage through building exteriors, cause, cure, prevention. Using flashing tapes & membranes on buildings.

What is the best way to flash around windows & doors and how should flashing tape be used at these openings?

This article shows best practices, common practices, and some not-so-good practices using peel-and stick flashing tape around windows, doors, and other building wall penetrations.

Article Series Contents

  • PEEL & STICK FLASHING MEMBRANES
    • WINDOW & DOOR FLASHING TAPE DETAILS - separate article

This article series discusses best practices construction details for building exteriors, including water and air barriers, building flashing products & installation, wood siding material choices & installation, vinyl siding, stucco exteriors, building trim, exterior caulks and sealants, exterior building adhesives, and choices and application of exterior finishes on buildings: paints, stains.

Portions of this article are adapted/paraphrased with permission from Best Practices Guide to Residential Construction by Steven Bliss, courtesy of Wiley & Sons.

Peel-and-Stick Flashing Tapes, Types, Uses, Applications

Typically ranging in width from 4 to 12 inches, these peel and- stick membranes greatly simplify the task of creating a continuous barrier to water entry around doors, windows, decks, and other problem areas. Flashing tapes are faced with reinforced polyethylene or foil on the outer surface and a peel-away paper on the adhesive surface.

The foil faced products may be left exposed to the weather permanently, whereas the plastic-faced tapes should not be exposed to sunlight and weather for more than 30 days (longer for some brands) since UV radiation will degrade the facing.

Comparing Modified Bitumen vs Butyl Peel and Stick Flashing Tapes

Most flashing membranes are made from modified bitumen, the same rubberized asphalt used in eaves flashing. Some use a more expensive butyl rubber core, which stays more flexible in cold weather and is more stable at high temperatures.

Butyl products also bond better to difficult substrates than modified bitumen and can be peeled off and adjusted during installation.

Moldable Flashing - Butyl-based

A unique butyl-based flashing tape from DuPont, called Tyvek FlexWrap®, has a wrinkled facing that allows it to be molded easily to irregular shapes such as the head flashing of round-top windows. It can also be bent to create a pan flashing at window sills without any cutting and folding at the corners. Despite the higher material costs, labor savings make this product appealing for tricky applications.

Applications for Flashing Tapes

These products offer several distinct advantages over metal flashings: They are easily bent or molded for an accurate fit, can accommodate settlement and shrinkage movement, are self-sealing around nail holes, and bond well to a variety of materials, including metal, wood, plywood, and vinyl window flanges.

Flashing tapes provide long-lasting waterproof protection if installed correctly. Oriented-strand board (OSB), concrete, and other masonry materials, however, can be problematic for some of the rubberized-asphalt flashings and may require priming for a good bond. Consult with the product’s specifications for compatible surfaces and priming requirements.

Guide to the Installation of Flashing Membranes

To obtain the best results with these products and be protected by the manufacturer’s warranty, it is advisable to follow the manufacturer’s recommendations. These vary from product to product, but generally they address the same issues: application temperature, priming, installation techniques, and compatibility with surrounding materials.

Temperature Effects on Peel-and-Stick Flashing Membranes

In general, the rubberized asphalt (modified- bitumen) products start to lose stickiness at around 50°F and will not bond much below 40°F. Unless you are working with a rubberized-asphalt product specifically formulated for low-temperature applications, a butyl-based product is a better choice in cold weather.

Very high temperatures can also be problematic for rubberized-asphalt membranes. When subjected to high temperatures and pressure, for example, when squeezed under a dark-colored metal flashing exposed to direct sun, the material will soften and begin to flow.

Unless formulated for high temperatures and labeled “hi-temp,” most modified bitumen will begin to soften between 185°F and 210°F. High-temperature formulations can tolerate up to around 240°F, but are generally not as sticky.

Substrates: Bonding Flashing Membranes & Tapes to Solid Wood, Plywood, Vinyl, Metal, OSB

Each manufacturer specifies which products are safe to bond to and which require priming. Solid wood, plywood, vinyl window flanges, and metal are usually fine as long as they are free of oil and dust. Some manufacturers of rubberized-asphalt tapes recommend that all materials be primed for best performance, particularly in cold weather.

Most require that concrete and masonry be primed, and some require the priming of OSB and gypsum sheathing as well.

Many published details show asphalt-rubber flashing tapes bonded to asphalt felt and plastic housewraps. While these are rarely listed as suitable substrates in product literature, manufacturers of flashing tapes claim that their products will bond satisfactorily to both these materials as long as they are clean.

Do not expect a good bond to dirty housewrap that has been exposed to the weather for a month or to any dirty job-site material. For that reason, it is always best to detail flashings and to layer materials so that they shed water even if the adhesive bond fails.

Compatibility Flashing Membranes & Tapes With Vinyl

Rubberized-asphalt flashings should not be in direct contact with flexible vinyl flashings. The asphalt compound will draw the plasticizers out of the vinyl, causing the asphalt to soften and flow and the vinyl to become brittle.

The rigid polyvinyl chloride (PVC) used in window flanges, however, is generally not a problem. Rubberized-asphalt flashings should also not come into contact with any caulks or sealants unless specifically formulated for that use. Like soft vinyl, sealants may react with the asphalt, causing it to flow and stain the adjacent materials, such as window flanges.

Butyl-based flashings are compatible with most construction caulks and sealants, but they should never be installed in contact with any asphalt-based products such as roofing cement or bituminous flashing membranes.

These may degrade the butyl and undermine its ability to seal. In these applications, rubberized-asphalt is a much better choice.

Watch out: FortiFlash, for example, is not compatible with EPDM [rubber roofing] or flexible (plasticized) Polyvinyl Chloride (PVC) based products. FortiFlash and Moistop E#-Z Seal are not compatible with some sealants. Consult with sealant manufacturer for compatibility information.

Applying Pressure is Important in Stick-On Flashing Membranes

Flashing tapes must be pressed firmly into place to ensure full contact and a good bond. Some manufacturers recommend using a hard rubber roller for best results.

Splashback Protection and Other Uses for Peel-and-Stick Flashing Tapes & Membranes

While most flashing tapes are used around doors and windows, they can be put to good use wherever water penetration is an issue. Other applications include band joists, deck ledgers, inside and outside corners, and any areas subject to frequent wetting.

On wall areas adjacent to a deck or abutting a roof, for example, where splashback or snow buildup is likely to wet the siding, sections of membrane up to 36 inches wide can protect wall assemblies. Make sure to lap all layers of flashing, sheathing wrap, and adhesive membrane so that water is directed to the outside of the building, even if the adhesive bond fails.

Caution re Cold-Side Vapor Barrier: Don't Cover Entire Walls with Peel-and-Stick Flashing Membranes

Watch out: In cold climates, covering an entire wall section with waterproof membrane will create a cold-side vapor barrier, potentially leading to serious moisture problems and wood decay within the wall cavity. A section of membrane up to 3 feet wide, however, is unlikely to cause problems.

How to Installing Peel and Stick Flashing Tape Over & Under & Along the Sides of Windows & Doors

Question: which is the right way to install peel and stick flashing below a window

How To Install A Window Flashing

2016/09/13 Pat said:

Can someone please clarify this issue? Most everywhere I've read about window flashing tape, it states to never apply it to the bottom of the window on the outside so water can exit to the house wrap instead of under the house wrap.

My siding crew taped the bottom of the window like shown in this article but I'm less worried about it because there's an open flap of house wrap below the window where water can eventually exit. Also, I insisted on a rain screen and the house wrap should let water escape so it should get stuck inside. Either way, I don't think taping the bottom is hardly ever recommended.

[Click to enlarge any image] This photo of flashing tape installed below a window and over the window's bottom flange or fin does not show the very best installation practice. Photos by D Friedman & Eric Galow, Galow Homes.

Reply:

Pat:

You're quite correct. The photo showing peel and stick flashing tape applied over the window bottom flange and onto the building WRP or housewrap is not a recommended detail and might trap water in the window rough opening.

Please see complete details at WINDOW & DOOR FLASHING TAPE DETAILS - separate article

Sources & Installation Manuals for Flashing Tapes and Membranes - where to buy, how to install

  • Avenco www.avenco.com Butyl flashing tape
  • Bakor, Inc. www.bakor.com Blueskin self-adhesive, rubberized-asphalt flashing tape
  • Berry Plastics Flashing Tape Manual, [PDF] Berry Plastics & Polyken Nashua Tape Products, distributed by various sources including Best Materials, retrieved 2016/09/13, original source:
    www.bestmaterials.com/PDF_Files/flashing-tapes-manual.pdf
  • Blueskin SA, Henry Company, 999 North Sepulveda Blvd., Suite 800El Segundo, CA 90245310-955-9200. Contact the company at E-mail: productsupport@henry.comPhone: 800-486-1278
  • Carlisle Coatings and Waterproofing www.carlisle-ccw.com Self-adhesive, rubberized-asphalt flashing tapes and membranes
  • Dupont www.construction.tyvek.com StraightFlash and moldable FlexWrap Butyl flashing tapes
  • Dupont Flashing Systems Manual, prior, [PDF] retrieved 2016/09/13, original source:
    www.dupont.com/content/dam/assets/products-and-services/construction-materials/assets/K17933-FlashingGuidelinesBEFORE-10-30-11.pdf
  • Dupont Flashing Systems Manual - current, [PDF] retrieved 2016/09/13, original source:
  • Fortifiber® Moistop® and FortiFlash® self-adhesive and nonstick rubberized-asphalt flashing tape.
    FortiFlash® is a waterproof flashing membrane produced by Fortifiber Building Systems Group®, a Fernley NV USA company. The product is a self-adhesive membrane reinforced by high-density polyethylene film that the manufacturer also refers to as “rubberized asphalt” and is described more technically as “a self-sealing SBS modified asphalt core laminated to a cross-laminated high-density polyethylene film reinforcement with a siliconized paper release sheet. Contact the company directly for advice on the safest and most effective solvent to use.

    • Fortifiber Building Systems Group
    Fernley, NV
    1-800-773-4777 for sales and technical assistance.
    Website: www.fortifiber.com

    Fortifiber flashing tape manual, [PDF] retrieved 2016/09/13, original source: http://www.fortifiber.com/pdf/install_guides/IG_window_flashing_method_a1.pdf

  • Grace Construction Products www.graceconstruction.com Vycor self-adhesive, rubberized-asphalt flashing tapes and membranes
  • Illbruck Sealant Systems www.willseal.com/usa Self-adhesive butyl and foil-faced butyl flashing tapes
  • MFM Building Products Corp. www.mfmbp.com FlexWrap (foil-faced) and FutureFlash self-adhesive, rubberized-asphalt flashing tapes and membranes
  • Pella Window Flashing Details, [PDF], retrieved 2016/09/13, original source:
  • Polyguard Products www.polyguardproducts.com Windowseal self-adhesive, rubberized-asphalt flashing tapes and membranes
  • Protecto Wrap Co. www.protectowrap.com Standard and moldable (Protecto Flex) self-adhesive, rubberized-asphalt flashing tapes
  • Sandell Manufacturing Co. www.sandellmfg.com Rubberized-asphalt, PVC, and EPDM flashing tapes
  • Typar Flashing Tape Manual, [PDF] retrieved 2016/09/13, original source: www.typar.com/assets/downloads/pdf/TYPAR_WPS_Install_Instructions_5-19-15.pdf
  • Zip Wall Installation Manual, [PDF] retrieved 2016/09/13, original source: sweets.construction.com/swts_content_files/102935/821515.pdf

Reader Q&A - also see the FAQs series linked-to below

On 2020-02-04 by (mod) - reliability & limitations of using peel-and-stick membranes as window & door pan flashing

Thanks for the photo and post, Richard;

I agree that durable pan flashing is a concern and that peel-and-stick membranes may not be up to the job; I prefer using a fabricated metal pan flashing and rely on the membranes only as an underlayment around the opening.

How To Install Blueskin Window Flashing Tape

And in a freezing climate, even a modest amount of water under a window or door and atop the tape-fabricated pan flashing can cause heaving, door opening problems, or longer-term damage.
We can read what manufacturers like Pella have to say about using flashing tapes and membranes,

at WINDOW & DOOR FLASHING TAPE DETAILS
where I include links to various installation manuals and guides
Typically you'll see that the instructions say 'install a window pan' OR you can rely on flashing tapes but with some additional construction details such as exact placement of beads of sealant.
Watch out: the principal shortcoming of relying on peel-and-stick flashing tapes, speaking from personal experience, is that they don't always stick well to all surfaces. I've had problems with Typar and other tapes coming loose from
- OSB sheathing

- Plywood sheathing

- housewrap

- even framing lumber if it's not perfectly dry, free from contaminants, and not mill-glazed

- use in cold weather, applied to cold surface
My friend and sister site Steve Bliss - BuildingAdvisor.com makes a similar point at 'Flashing Membranes' at buildingadvisor.com/materials/exteriors/flashing-membranes/
Let's see if we can find some research on the durability of window and door pan flashing that relies on tapes alone.

Watch out: however it's also the case that window and door pans should be designed with slope and with an open exit along their outer face so that any water that enters the pan will drain out. I realize that 'should be' is arm-waving; nobody frames a window or door rough opening with an outwards pitch on the bottom horizontal member.

That's where using a pre-fab metal or PVC pan flashing can help us as those are often fabricated with the necessary slope.
Below: a PVC door pan flashing from SureSill, https://www.suresill.com/ as sold at Home Depot stores


On 2020-02-04 by Richard - most all peel and stick membranes are not designed nor warranties to hold standing water.

Interesting and educational piece.

Our efforts in this area have discoverer most all peal and stick membranes are not designed nor warranties to hold standing water.

Standing water such as a window will pan flashing.

[Photo above of Envelopeseal peel-and-stick membrane used as a door pan]

On 2019-09-02 by (mod) - can you use flashing tape over top of step flashing?

Not if left exposed to the weather

On 2019-09-02 by Anonymous

can you use flashing tape over top of step flashing

On 2017-10-12 by (mod) - flashing tape integration with housewrap

Anon: removing self-adhesive flashing tape can give you a devil of a time if it's well-adhered to a surface.
if the flashing tape was applied to housewrap, we'd cut the housewrap above and alongside the flashing tape, then pull it away; we install new housewrap as needed up under the lower edge housewrap just above the cut-area
If the flashing tape was applied directly to wood or other hard surfaces you might find it slightly easier to remove by heating it a bit with a hair dryer. It's difficult to pull off and almost impossible to pull off without damaging the wood or other surface below - except when it wasn't pressed firmly in place onto a clean dry surface in the first place.

On 2017-10-12 by Anonymous

How do you remove once applied

On 2017-03-14 by (mod) -

Yes, assuming you're going to cover that underlayment with new roofing material. But I'm unclear why you'd need an adhesive seam sealant on roofing felt underlayment since if the felt is in poor shape or damaged normally it would be removed and replaced, or a small damage area would simply have new felt overlaid in that spot.
Normal roofing felt under shingles is absolutely not a water barrier since it is punctured by the roofing nails.
If you need an underlayment that seals around roofing nails you'd be smarter to use an ice-and-water shield product that is wider and more economical in this application than flashing tape.

Watch out: however in my experience peel and stick membranes do not bond well to roofing felt

On 2017-03-14 by MFP

Can this be used to cover 'seam' between existing sheets of roof felt which have separated in parts?

On 2017-01-22 by (mod) - don't apply flashing membranes in cold or wet weather

Do not Apply in cold / wet weather

On 2017-01-22 by 4000 elevation

Does this say to NOT use in climates that get cold, snow, or just to not APPLY during cold season?

On 2017-01-20 by Anonymous

how long can the peel and stick stand the exterior with out being covered from the sunlight ?

On 2016-09-14 by (mod) - never apply it to the bottom of the window on the outside

Pat,
Thank you for asking: you're entirely correct that our photo of flashing tape set OVER the window flange of a new window installed into a R.O. is not the best practice.
To have space for illustrations and source citations I've included your question and a very detailed reply at WINDOW & DOOR FLASHING TAPE DETAILS
There you'll see that flashing tape IS used below windows but best practice installs it under not over the window flange. Best practice includes a window sill pan OR fabricates one from flashing tape.
Take a look, comment, and let me know what questions remain. Thanks. -Daniel

On 2016-09-13 by Pat -

RE-posting
Pat said:
Can someone please clarify this issue? Most everywhere I've read about window flashing tape, it states to never apply it to the bottom of the window on the outside so water can exit to the house wrap instead of under the house wrap. ...
My siding crew taped the bottom of the window like shown in this article but I'm less worried about it because there's an open flap of house wrap below the window where water can eventually exit.

Also, I insisted on a rain screen and the house wrap should let water escape so it should get stuck inside. Either way, I don't think taping the bottom is hardly ever recommended.


...

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Recommended Articles

  • FLASHING on BUILDINGS - home
  • UNDERLAYMENT DOUBLE vs SINGLE where we discuss use of flashing membranes at roof eaves

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How To Install Blueskin Window Flashing

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  • Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
  • John Rudy, Advantage Home Inspections, Flemington N.J. 08822 home inspector, 908-806- 6364, Home, Radon & Termite Inspections, Central & Parts of North New Jersey, email: jonadvantage1@yahoo.com

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Window flashing is an important component of any home build or remodel. Too many people forget or just don’t know how to properly flash a window, so we thought we’d give you a little introduction to the basics of window flashing. If you have any questions about window flashing at the end of this guide, be sure to refer to your window’s manufacturer guidelines, or feel free to give the Zeeland Lumber & Supply team a call for a little help. Let’s get started:

What is Window Flashing?

Window flashing is a weather-repellent material that is installed around a window unit to protect both the window and the window framing from water damage.

When is Window Flashing Installed?

Window flashing is installed at the same time as the window unit. Typically, flashing a window is a two-part process. The first half of window flashing occurs when you or your builder preps the rough opening for the window’s installation. The second half of window flashing occurs once the window unit is secured and squared within the rough opening.

Window Flashing Terms to Know Before You Start:

  • Drip Cap –An aluminum attachment installed on the very top of a window unit. Works to stop water from seeping and pooling at the top of a window unit. Minimizes the potential for water damage.
  • Flashing –A water-repellant adhesive that’s applied over window flanges and sheathing to seal out any potential leaks in or around a window.
  • Head Jamb –The top of a rough opening. This is where the top of a window unit goes when installing.
  • Jambs –The vertical sides of a window opening.
  • Rough Opening – The opening left for a window when a home was framed. It looks like an open square in a framed wall panel, and has special reinforcements to properly hold in a window unit. Learn more about framing basics and rough openings here.
  • Sill – The bottom edge of a window rough opening. This is what the window unit rests on when it’s installed.
  • Window Unit –The entire window, from the frame that holds in all of the components of the window to the sash and glass that make the window function. All combined, these parts make up the entire window unit.
  • WRB – Weather Resistive Barrier, also known as house wrap. This is a thin, weather-resistant sheet of material that’s wrapped around a home before windows, casing, or siding is installed. It affords your home another layer of protection from the elements.

How is Window Flashing Installed?

How To Install Blueskin Window Flashing Installation

Every window manufacturer offers specific instructions for flashing around a particular window unit. Depending on the type of window, its construction, and its shape, window flashing may follow a few different steps. It’s always best to follow manufacturer instructions whenever possible. To give you a general idea of the window flashing process, here’s a basic step-by-step for installing window flashing for a rectangular window in a residential home.

1. Cut back WRB (weather resistive barrier)

a) Your WRB should be wrapped over the rough opening of the window. When you’re ready to install the window
unit, you’ll cut back the WRB.

b) First, make a vertical cut in WRB at the center of the window opening, from the top of the opening to the
bottom. Then, make horizontal cuts along the top and bottom of the window opening, pulling those two side
flaps back from the opening, and securing them with a small piece of tape for now.

c) Make 45 degree cuts away from the corners on the top of the rough opening. When you fold and tape the flap
at the top of the rough opening, you should end up with something that looks like this.
(Photo courtesy of Marvin Windows)

2. Install the sill pan flashing.

Henry Blueskin Flashing

a) When installing sill pan flashing, or the flashing at the bottom of the window, you have a few options in the
material. You can use adhesive peel and stick flashing, or you can opt for a pre-shaped sill pan, which will help
collect water and direct any runoff away from your home safely. This instructional diagram from Marvin
Windows shows another option, a combination of a sill wedge and self-sealing adhesive flashing.

b) Choose the sill pan flash option that’s recommended by your manufacturer. If using peel and stick window
flashing, ensure that the flashing extends the full length of the sill and up at least six inches on either window
jamb side.

3. With the sill pan flashing done, wrap the side WRB panels around to the interior of the rough opening and secure, as
shown in figure (b).

4. Apply sealant

a) With WRB secured and sill flashing in place, you can now apply a small bead of sealant in preparation for the
window unit.

b) Do not apply sealant to the bottom or sill of the window rough opening. The bottom of the window must
remain open so water does not become trapped within the window unit.

c) Apply sealant on top and sides of the window rough opening. Start ¾” of an inch from the corner on each side,
and stop ¾” from the end of each side. This will allow for any water that does enter the unit to escape easily and
without damage. If you seal all the way around each corner, water will be trapped in the window unit and can
cause mold and wood rot.

5. Install window unit.

a) At this point, you can install your window unit. Follow manufacturer instructions, or check out this blog for
more information on properly installing a window unit. Ensure that the window is plumb and square before
finishing your window flashing.

6. Insulate around window unit.

a) Follow manufacturer instructions, using either expanding spray foam or fiberglass insulation.

7. Apply peel and stick flashing to window jambs, extending flashing beyond the sill, and 4 to 5 inches above the top of the
window.

8. If your window has come with a drip cap, now’s the time to install it.

a) The head jamb of a window is the most vulnerable to water damage. That’s why many manufacturers provide
drip caps with their windows. Drip caps are fastened to the sheathing directly above a window and protrude
slightly to keep water from entering the window unit. If your windows do not come with drip caps, you can
purchase them from your local supplier, or fashion your own with aluminum coil and peel and stick flashing.

b) Install the drip cap according to manufacturer instructions. Most windows that come with drip caps are
manufactured in a way that the drip cap will fit conveniently at the top of the window. If using your own drip
cap, simply adhere the piece directly above the window so that any water will flow away from the wall and
window unit, and out onto the glass of your window.

9. Apply head jamb flashing and finish up.

a) The final step is to apply the head jamb flashing. This strip of flashing should go horizontally across the top of
the window unit, extending at least six inches beyond the window jambs.

b) With that, you can fold down the top flap of WRB, tape it in place, and you’re all set.

At this point, you’ve completed your window flashing, and your window is ready for casing and siding.

Window flashing is an important step in the home construction process. Too many people don’t know how to or forget to flash windows properly, which can lead to costly water damage within your home. By following these simple steps, and taking just a little extra time when installing your windows, you can ensure that the home you’re building or remodeling is watertight and secure for years to come.

Getting ready to install windows on a new home or remodel? Zeeland Lumber & Supply can help! We have all the supplies you need, from top-of-the-line window selections to simple, peel and stick flashing adhesive. Start your next project off on the right foot — get everything you need at Zeeland Lumber & Supply. For the window flashing supplies you need, give us a call at (888) 772-2119 or stop into one of our locations today.