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Windows Resources

When Does a Window Need to Be Flashed?

Wood rot, mold, structural damage, and insect infestations—there’s nothing pretty about water seeping into the cracks and seams of your home. Unfortunately, a poorly installed window that lacks proper flashing can be a gateway to these unpleasant phenomena.

Flashing is an essential component of proper window installation. It catches rain that is blown at an angle onto your home. Siding isn’t enough protection between your house and the rain and moisture that occurs outdoors, which is why you need to put an extra barrier between your window and siding. It’s safe to assume that most window installations need some form of flashing, and most residential building codes require it.

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When Doesn’t Window Need Flashing?

Certain window designs may not need flashing. Channels can be built into the window frame that directs water down the side of the window. But it’s important to do your research. The convenience of skipping a step is not worth risking the structural integrity of your home.

Choosing a Window Contractor

Flashing installation shouldn’t be an option, but some contractors overestimate the effectiveness of siding in preventing moisture from entering the openings around the window. Other contractors install flashing but fail to integrate it correctly into the water-resistive barrier.

Unfortunately, hurried or negligent workmanship is too common, which is why you need to ask about window flashing when you choose a contractor or are put in touch with a sub-contractor. Make sure he or she is willing to discuss the details and not just write off your questions about flashing. Check references, read online reviews, and verify licenses and insurance. You want to be sure your contractor won’t make a simple mistake or oversight that could cause serious problems for you down the road.

Types of Flashing

There are three main types of window flashing, including:

  • Tape: a self-adhering membrane that’s flexible and durable. This is the newest and most common form of flashing for both new construction and remodeling projects.
  • Sheet metal: a thin yet flexible option used with many different types of building materials including brick and stucco.
  • Vinyl: an affordable, functional, and durable flashing option—although it may not be the best choice for extreme cold weather. It’s most commonly used in combination with vinyl siding.

Don’t just make a guess about which window flashing will work best for your home. Research thoroughly, ask questions, and consider factors such as your local climate, the building materials used on your home, budget, and energy efficiency. Responsible, experienced, and knowledgeable installers can still make mistakes that lead to leaks, even if it’s just an error in judgment over which flashing material is best suited to the project. It never hurts for you to read up and have an educated conversation about your options with a professional.

Replacing Your Windows


When a contractor begins the process of replacing your windows and finds signs of rot and mold, this may mean that the flashing was not initially installed the correct way, or the outdated method functioned well for a time and then became ineffective with age. Older windows were installed differently than most new ones are. In fact, in some cases caulk was the only moisture barrier used between window and siding—so older houses especially may have this issue. If you suspect water may have penetrated your windows, don’t wait to replace them. Act fast before the damage worsens, or you may find yourself facing a much larger remodeling bill than you expected.

Installing Window Flashing the Right Way

If you’re DIYing your window installation, be sure to read all the manufacturer guidelines on the products. The manufacturer knows what conditions are optimal for their product, and they want you to get the best performance out of it. If the instructions on your window vary from the instructions on your flashing product, always follow the instructions that require doing a little more work or care—because it’s better safe than sorry.

If you’re hiring a professional (which is recommended), don’t be afraid to ask questions about flashing. It’s better to ask a hundred questions now than to pay thousands of dollars in repairs down the road. Installing flashing is not a time-consuming or pricey aspect of replacing or installing windows, so make sure your contractor is willing to take all steps necessary to ensure the windows are watertight and up to code.

You can do everything else right when it comes to building or renovating your home, but glossing over such a small but important detail could cause major problems. Hire a window contractor you can trust, and invest in quality materials. You won’t regret paying special attention and care to your window flashing.

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