Window Installation: Important Steps

Whether you do the work yourself or hire a professional local window installation expert, there are a few things which need to be done in order. However, before you start with the window installation process, make sure that your new window will fit! Most windows are custom sizes. Made to the exact required size of your window opening. Once in a while you can find a “close” fit, and with a bit of carpentry you can modify the frame and the trim, and can make it work. Generally, since windows are designed to last decades, it’s best to order a properly fitting custom window, properly sized. The cost will generally not be any more than an “off the shelf” window. You’ll just have to wait for it to be made.

So let’s assume you now have your new window, and you’re ready to install it. Make sure you have a few tools handy to unscrew the old window anchor screws, and to pry off the molding around the window frame inside your home.


Removing the Old Window Trim, Casing and Guide Track

Pry off the casing with a prybar – but be very carful not to tear the wallboard or paint, or you’ll be faced with a lot of repair work. There’s usually a jamb extension on the window which brings the window level with the wall. That will have to be removed as well. Once you remove the trim and the screws which hold it against the jamb, the window should slide out. Take care not to break the panes.


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Prepping & Repairing the New Window Opening, Inspection & Dry Fit

With the window out, carefully examine the opening for any damage. Old windows tend to leak and rot out the jamb. In that case, you’ll have to either repair the section or replace it before installing your new window. Make sure that the opening is about 1/4” larger than your new window. If it’s too large, you’ll have to augment the jamb to reduce the extra space. If it’s too small, than you’ll have to reduce the size of the jamb.

There’s also a piece of ripped wood lining the jamb on the exterior side of the jamb. This is called a window stop. It’s appropriately named, since it’s job is to stop the window from sliding out through the opening. Usually, they stay I good shape. But again, if you need to replace it, then that’ll need to be done before the installation of the new window.

Dry fitting the window

Installing Your New Window

Before you finalize the installation, do a dry fit. It should be snug and level. If it’s not, check the jamb, and stop again. That’s usually where problems lie.

The actual window installation is straight forward. It’s the reverse of the removal process. But first, apply a bead of silicone along the inside edge of the window stop. Then, place the window into the opening by sliding it forward until it’s snug against the window stop. Use a level to make sure it is level. If it’s not, you may have to use some shims to bring it into level.

Typically, new windows come with their own hardware, which is to say – 4 screws. It may not appear to be much, but four screws is all you need. You’ll notice that your new window will have holes pre-drilled for the installation screws. One closer to the top of the frame, and one closer to the bottom. That’s two screws per side. Use the screws to attach your new window to the jamb. Take extra care not to overtighten them! This will distort the frame, and the window will not operate properly. Test the window by opening and closing it several times – while watching carefully to make sure the spacing along the track and the frame remain constant – while you repeatedly fully open and close the window. Do this several times, checking the top, bottom and sides for smooth operation. The screws should be barely snug. Just tight enough to hold the window in the frame, and not a turn more!

Insulating Your New Window, Adding Extension Jambs and Replacing the Trim Molding

With your new window now installed, you’ll probably feel the draft from between the jamb and window. This gap will need to be filled before any trim is installed. If the gap is very large, you can use fiberglass insulation. Typically, however, you’d probably use an expanding foam insulation designed specifically for window and door installation applications. Take extra care when you buy the foam insulation. The standard expanding foam used in construction will keep expanding as it hardens and the pressure it exerts can distort the window – and in some extreme cases – even break the pane. The foam insulation used for windows and doors is a “low expansion” type which will not distort the window. Once it’s dry, just use a sharp contractor knife and trim off the excess to allow the re-installation of the trim.

This is the time to upgrade your trim! When you install a new window, the old trim is removed, and it’s your big chance to match the trim with your new decor and style. Keep in mind that you should only use thin finishing nails – and use a ball peen hammer – to avoid damaging and dimpling the new trim. Ideally, a finishing nail gun should be used. Unless you’re skilled with a hammer! You can rent one from your local tool rental outfit for sure.

Before you finalize the installation, cut all the pieces using a miter saw. Whether it’s an electric saw or you’re doing it by had, make sure you allow for the thickness of the blade! You’ll see that it counts. Otherwise you end up with fat beads of calking between the seams. If your window frame is not 100% square, you may have to play with your angles a bit to get a perfect fit. Sink a couple of nails just deep enough to hold the trim against the wall. Once all the pieces are cut and fit perfectly, then finish the installation by adding a few more nails. You don’t have to over do it. Apply a bit of caulking, then you’re ready for the paint job!

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