How to Install Window Flashing Tape & What Happens When You Do It Wrong

August 5th, 2019 BY First American Roofing

If you are like most people you have no idea what window flashing tape is, let alone how to install window flashing tape.

While it may seem like a tedious and minor step while installing a new window or replacing siding, it’s crucial you get it right.

Far too many homeowners have window flashing tape installed improperly, or not at all, and this causes a LOT of problems.

Putting new siding on your home is a beautiful upgrade, and can extend your home’s exterior and curb appeal for years to come. But, it will all be for nothing if your windows and doors are not properly sealed with flashing. Flashing tape is installed beneath your siding around your window to seal it from air and moisture, which if it gets behind the siding, can cause rot, cracking, and leaks.

Improperly Taped Windows Cause Major Problems

We often notice in houses built 15-20 years ago that the windows have not been taped to today’s standards, or not taped at all. We will be on a re-siding project, and when we pull off the old siding, end up finding rot that now needs to be repaired before the new siding is installed. There have been bad instances where we’ve pulled the siding off and the sheathing is completely rotted out and even worse, can be spread to the wall studs, insulation, and deck ledger board. This rot absolutely needs to be replaced, re-built and cleared of mold before your new windows or siding get installed.

Damage Prevention With Window Flashing Tape

window flashing tape-new windows after installation

The rot and mold damage occurs when water gets behind the siding or window well. This moisture can get in between your siding and walls, seep through the insulation, and cause damage both inside and outside of the home. Proper installation of flashing around the windows, and having a seamless house wrap can prevent this moisture penetration.

Flashing comes in a few different forms. There is vinyl flashing, that is commonly used in combination with vinyl siding, and works great for cold weather. Sheet metal flashing is thin and flexible and can be paired with brick or stucco. The most common, and newest form of flashing is the self-adhering tape. New construction and remodeling projects would be remiss without this flexible, durable, easy-to-apply flashing tape. A good flashing tape will be airtight, UV resistant, all-weather, and compatible with most common caulking and sealant materials.

It’s very important to find a contractor who will not only install flashing properly around your windows and doors, but that will check for mold and further damage before installing anything new. These discoveries can prolong the project but are crucial to preserving your new siding and exterior. It’s important for you to know about this process as a homeowner, so you can ask the right questions, and make sure you get the proper protection on your home. We want to help you preserve the integrity of your home and your investment for years to come.

How To Install Window Flashing Tape

close up to window tape-window flashing tape

As you can see in our video, the self-adhering flashing tape is a simple peel and stick system that goes on fairly seamlessly. The flashing will be wrapped over the rough opening of the window, which is what will be covered eventually by siding. It’s important to cover all sides, top, bottom, and corners. Cut the corner tape at 45-degree angles to allow for folding over and so the seam is completely flush with the window. The tape will overlap itself on all corners to create a 100% water-resistant barrier.

As easy as it seems to install, we insist you have your windows and flashing professionally installed. Let the pros handle it! Don’t be the guy who tried to DIY and has it backfire years down the road. We have made it our duty to use only the best materials, with the best installers and to give you an end result that was better than when we started. Preserve the longevity of your home with First American Roofing. We want to be your resource so please call us for questions and get started on a FREE estimate today at 608-247-5413.

However, if you insist on completing this project yourself, there are a few things you need to make sure you get right. First off, make sure you use quality flashing tape. If you picked the off-brand tape that was on a buy one get one sale, you’ll get off-brand results which could cost you big time down the road.

When you go to install window flashing tape, make sure your window is both the right size and the flashing tape adequately covers the whole seam. It is crucial the tame covers the whole seam! Also, make sure to check the package for application temperatures before installation. This will ensure optimal seal and protection of your window sill. If it wears away 5 years down the road you’ll be left with a leaky window and severe water damage. So if you aren’t positive you can do this on your own – call a professional. It simply isn’t worth the risk

If you are interested in more reading, be sure to check out our post breaking down the best gutter guards in 2024!