Window Replacement in Portland – 3 Important Installation Techniques to Prevent Water Damage

September 16, 2020


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Why is getting your windows replaced different in Portland Oregon than it is in Phoenix Arizona or Los Angeles, or even Bend Oregon? It all boils down to climate. Portland receives 40.7 inches of rain annually. Los Angeles gets a mere 11.5 inches, Phoenix a whopping 7.6 inches, and Bend Oregon receives only 11.7 inches, even though it’s still in the same state as Portland. So Portland gets three to five times more rainfall than those other cities we compared. custom windows Toronto

The reason correct window replacement is so critical in Portland is that because of the high annual rainfall statistics, if done incorrectly, rain leaking into your home can cause major water damage to your wood framing, insulation, drywall, paint, and flooring. And because of Portland’s rainfall and high average humidity, mold can also form in walls and cause many health issues for the home’s inhabitants.

The average cost to repair water damage in Portland is $5,000 so getting your windows replaced correctly in Portland is very important. Whether you’re doing your own window replacement or having it done by a local contractor, there are three main techniques which need to be used to ensure a leak-proof installation. Below, I will list these in their order of importance, not necessarily in chronological order.

  1. Flashing above the window trim. The majority of window installations require the installer to cut around the window in order to remove the old one. Most old windows, especially the aluminum ones, have nailing flanges around the perimeter. In order to remove the old window and install a new one with flanges, a cut must be made around the perimeter of the window.

Once the new window is installed, wood trim is placed around it and caulked. But caulking alone at the top of the trim won’t keep water out. Metal flashing, called z metal, needs to be properly installed behind the siding and over the new trim. Some contractors in the Portland area don’t install this important piece of flashing. It takes more effort to feed it behind the siding. They just caulk it and get paid by the homeowner, knowing that after their one year warranty is over, it will probably start to leak. So z-metal flashing, is the number one technique I recommend to prevent water infiltration.

  1. Sealing the nailing flange to the wall sheeting or building paper. The second most important technique to implement during the window replacement process is to properly seal the window’s nailing flange to the wall sheeting. How is this done, you ask? There are two products I recommend which are readily available in the Portland area. One is Tyvek tape. This is a product made by Dupont and it works beautifully for sealing the flange.

After the window is placed in the rough opening, the installer should apply this tape around the window perimeter making sure half the tape adheres to the new vinyl window nailing flange and the other half adheres to the wall sheeting or sub-siding. This should be done only if it’s not raining (which is seldom in Portland) and the wall sheeting is dry. Apply tape to the bottom flange first, then the sides, and finally the top flange. If your home has building paper over the wall sheeting, apply the tape to this paper.

  1. Caulking generously. There are several times you need to apply caulking during the window replacement process. The first application is before you set the window in the opening. Evenly apply silicone caulking around the perimeter of the window opening where the nailing flange will lay over it.

Then place the new window flange over the caulking while it’s still wet. Apply a second bead over the flange and Tyvek tape before you install the wood trim around the new window. This should be silicone caulking, as well. The trim should be installed over the caulking while it’s wet.

The final caulking should be applied after the trim is installed. This time use a good, exterior caulking that’s paintable as you’ll probably paint the new trim and the siding adjacent to it. Caulking should be applied to the gap between the new trim and the siding. Use white caulking in the gap between the new window and the new trim. Don’t scrimp on the quality of the final caulking used.

These three techniques, done correctly, will ensure your window replacement project to be leak-free, even in a city like Portland Oregon where over 40 inches of rain falls every year.


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