New Windows Old Home | New Windows for the New Year

December 31, 2017

If you are thinking about installing new windows in your old home in 2018 we have a few general tips for you. Hopefully this will give you an overall understanding of what’s involved in installing new windows in an old home, so you are not overwhelmed by the project. You should also take a moment to watch the video below to see what you may be getting yourself into. If the task seems too tall, just contact the Window Repair Guy and let us do the dirty work for you.

Buying New Windows that Fit

The first thing you need to do is remove the storm windows and/or screens, so you can measure the opening. Typically, these are packed with caulking which will need to be removed for accuracy. Take the trim off so you can take a precise measurement of the existing rough opening for the old windows.


When buying your new windows, you may not be able to find something with the exact same measurements. So, to save yourself a lot of aggravation purchase windows that are the next size smaller. For example, if your old windows measure 36 ½” wide and you think you feel a ¼” gap around the window. Don’t be tempted to purchase something that is 37” wide. You will be totally frustrated. It is much easier to shim or fill that gap with lumber, than it would be to make the rough opening wider. Trust me!

And don’t be too concerned that the smaller size will obstruct your view or change the look of your home. New windows today feel larger than old-style windows due to the way they are designed.

Double Check the Window Opening Measurements

Once you remove the old window you can really get an accurate measurement. Take 3 vertical and 3 horizontal measurements of the rough opening. With the new windows laying on the ground or securely propped up, measure the extremities of the new window frame. With any luck your new windows will be narrower and shorter than the rough opening and you can carry on to the next phase with ease.

New Windows

Clean up the Rough Opening

Clean up the rough opening of the window using a Sawzall. Cut back the siding and interior protrusions so that everything is flush with the 2×4 framing. Now you can compare the dimensions of the opening to the new windows and fill the extra space with ½” or 1” lumber as needed. To create a smooth mounting surface that is the full depth of the opening, measure the combined depth of the 2×4’s and the siding. Then simply cut your spacers to that dimension. So, if the old-style 2×4’s are close to 4” and the siding is 1” thick or so, you will cut your ½” thick strips about 5” wide.

New Windows

When installing the bottom spacer board, you may need to shim it on one end to make it level. Set the lower spacer board in place and lay a level on top. Slide some shim stock at one end or the other until the spacer board is level, then nail it in place. Do the same for the vertical spacers. Once the spacers are installed you should still have a ½” to ¾” difference between the rough opening and the window itself. This will allow for final shimming as you install your new windows.

new windows

Secure Your New Windows

Secure the new windows in place by driving a tack or large head nail in every hole in the window flange. This not only holds the window in place, but it also contributes to the tight seal of the new windows. Don’t be tempted to skip every second hole. You will be inviting in a cold draft in the middle of winter.

new windows

Install the Window Trim

Depending on the condition and dimensions of the original window trim you may be able to reuse it. However, in my mind, the finished product will be much cleaner if you go ahead and install new trim. This true for both the interior and exterior trim. And as the mentioned in the video, caulk the heck out the window both inside and out to prevent any cold drafts. You may want to take a look at our Window Caulking Tips article.

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Thinking about installing new windows in your old house in 2018? Contact our support team at (815)-634-8922.