Choosing and installing replacement windows

Normally I like to do every last thing I can on my house. It saves money, and I just love the work. However, for the big job of replacing all the windows on my house, plus adding all new siding, I hired out the work to a trusted local contractor. But if you read on, you’ll find out how to choose the right materials and how to keep your contractor honest. You might even learn how to tackle the job yourself.

In an earlier blog, I installed a window in my garage, to give me a nice view and some natural light in my workshop space. So it bothered me a little to just watch the work this time! But it was a wise choice. My contractor has better ladders, more workers, and more know-how, and I just have too much work at the moment. That said, watching it happen, I realize that this is a job a lot of people could do.

In the milder climate of the Pacific Northwest, where I live, a lot of houses were built with just a single skin of exterior-grade plywood. No house wrap, and no siding. That’s the deal on the 1979 fixer-upper we bought in 2015. So adding windows is a little bit different than it is on a house with plywood sheathing plus siding. But not much.

Modern windows have a simple nailing flange all around the outside. You just sit the window in the rough opening, make sure it is level, and nail or screw that flange to the exterior walls. Done. In my case, we could simply nail that flange onto the plywood exterior, wrap everything with house wrap, nail trim boards around the windows, and then nail on our siding of choice, bumping it up against that trim.

For a house with existing siding, you would just need to work around that, cutting it back or removing some of it, or just pulling off the trim boards and replacing them afterward.

The problem on houses like mine is that those window flanges are nailed right onto the studs, and then the T1-11 exterior plywood goes on and covers them up. That meant we had to cut off a strip of that plywood around each window to access those flanges and remove the windows.

A word about choosing windows. We were getting rid of the worst possible windows, made of aluminum, another cheap signature of the era of disco and polyester. Terrible looks and terrible energy efficiency. The usual choice these days is vinyl windows, which used to be considered cheap but have gotten way better of late, with most offering the Energy Star rating. That said I went with Marvin’s Integrity windows, for a variety of good reasons. Made of a special type of fiberglass, they offer the best longterm value on the market.

Building experts agree that Marvin’s fiberglass is super-energy efficient and super durable, meaning it won’t warp or crack like vinyl sometimes does. Also, it expands and contracts very little, just like the glass inside the frames, meaning the seals all around that glass will not fail. And last, its mitered corners are crisp and clean-looking, unlike those melty miters on vinyl windows. Last the Marvin Integrity windows are available in a range of colors, applied in a thick fiberglass layer that promises a lifetime of service.

You could go even higher end, choosing windows clad with wood on the inside, but I’ve got plenty of wood inside my house, and I like the clean looks of the fiberglass interior.

Whichever windows you choose, the KEY to a good installation is making sure the windows are level and square, so they will operate smoothly, and then making sure the window is flashed correctly. Flashing is the overlapping layers of metal, plastic, or rubberized material that go all around the window, under your siding, to catch any water that gets under there, and send it down over the house wrap instead of letting it inside the window frame to cause rot and damage.

Anyway, check out the following pics to see the whole process. Next up will be applying the window trim and all the siding. I’ll do a whole blog to explain our choices on that.

The first step is to pull out all the interior trim so you can measure the rough openings and buy the right-size windows. We have a lot of wide windows, so we went with sideways sliders.
Next you need to get access to the nailing flanges on the outside of the windows. On my house, which just has a single layer of painted plywood on it, that meant removing a strip of that plywood all around. On a house with siding, you might need to remove the trim boards around the windows, or some of the siding.
Once the guys could get at the flanges, they pulled all the nails and the windows came right out.
To make a level surface for attaching the new windows, we had to nail on strips all around to fill those gaps we created.
This is when the flashing happens, one of the most CRITICAL steps. It starts at the rough window sill, where an adhesive rubberized material is applied.
Then, overlapping that bottom piece, the side pieces go on. The idea is the same as it is with shingles: You overlap them so they shed water as it drips down.
Where he had to cut the material to get it into the inside corners, the contractor applied extra little adhesive pieces to cover the tiny gap.
Now the new windows could slide right in! That extra flashing at the top will get overlapped by the house wrap, which will cover all the walls later and complete the water-shedding envelope. Trim and siding will come after that.
Once the windows were shimmed level in their opening, and we made sure they slid and closed easily (a good check for squareness), the guys just drove screws through the flanges and the window was locked in place for life.
Marvin even supplies little adhesive corners to cover the gaps where the nailing flanges fold outward and create a tiny gap. As I said, the house wrap is coming up next, which will cover all the edges of the window and ensure that water sheds downward not inward.

11 thoughts on “Choosing and installing replacement windows

  1. I’m a lot like you when it comes to wanting to do most of the work on my own home, but something like residential window replacement is something that I don’t think I want to deal with. I like that you pointed out that choosing the right contractor was helpful, and that they had all the right tools to get to job done, that would probably make doing a window replacement difficult otherwise. I’m glad I found your article, and hopefully I can follow your tips to getting a quality residential window replacement done on our home!


  2. I didn’t know that if a window looks terrible, it probably has terrible energy efficiency. I had no idea that windows could affect this. I can definitely see why it would be important to replace windows, especially if moving into an older home. After all, you want to make sure that your home is energy efficient, as well as looking nice. Perhaps it’s time for me to consider my window situation and see what my options are.


    1. No, I didn’t mean to imply that there is a connection between how a window looks and how it performs. Of course, old windows were not made to the same energy standards as today’s windows are, so very old windows are probably poor performers. Look for the Energy Star rating on any windows you buy.


  3. Window replacement is one of the important part of home renovation. Different materials are there for window replacement such as: wood, fiberglass, vinyl, aluminum, clad windows, double-hung windows Also different variety of styles are there and as per your needs you select one. Different window has different installation process. One of the important advantage of window replacement is that sunlight can enter to your home so it gives light to your home. Before installation of your window you should know the installation process or you can take the help of a professional.


  4. How do you then make the window weather tight? Wrap below the nail fin and then again over the nail fin? What stops the water from getting in above the membrane since you did not use z-flashing?


    1. Hey, Wayne–Actually, we cut a flap in the house warp so it could be layered over the top of the nail fin. Marvin also supplies an adhesive tape that goes over the nails fins first. Then the flap goes over. See the Hardie Plank post for the details.


  5. I could see the importance of removing some of the sidings if your new window seals don’t quite fit. My wife and I want to replace our windows just because the design has been the same since 1975. We’ll have to use your tips so that we can try and keep our windows updated.


    1. Hi, Sam–
      Yeah if you want to use the easiest windows to install, with nail-on flanges, some (or all) of the siding will have to come off. In my case, there was only plywood on the house to start with, so we just nailed on the new windows, and then installed the new siding over the plywood. Great opportunity to do both upgrades in one shot!


  6. My wife and I are thinking about installing new windows once we are done remodeling our living room. I like your point about how modern windows offer an energy star rating. We’ll be sure to look for windows with a good energy efficiency so we can save money on utility bills.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s