New Window Replacement Tips

What to Consider When Measuring for New Window Replacements

By Mark J. Donovan

When replacing a window make sure to first remove the interior window trim molding, before you buy the window, so that you can obtain an accurate measurement of the rough opening window frame. Use a measuring tape and measure both the horizontal and vertical dimensions.

Also measure from the lower corner to the opposite upper corner to see how square the rough window opening is. Repeat this step from the opposite corners and compare the two measurements. If they are the same, then the rough opening is square.

If they are not the same, you may have some difficulties installing the new window, particularly if there is little clearance between its outer edges and the rough opening of the window frame.

Also when selecting a replacement window make sure to order one with dimensions such that there is between ¼ and ½ inch of clearance around all of its sides, relative to the rough window frame opening. This will enable you to square up the window with shims and ensure that the replacement window operates properly.

If you buy a replacement window that is too wide for the window frame opening, such that there is less than ¼ inch clearance between the window frame opening and the window sides, then you may need to temporarily remove the jack studs and rip them to make them a little thinner.

After ripping the jack studs reinstall them. You can safely remove up to a ½ inch in thickness from the jack studs and still have them structurally adequate. Always replace the jack studs after removing and ripping them.  The jack studs support the window header. Without the jack studs the window frame could sag over time and cause the window not to operate properly.

If you order a replacement window that is slightly too small for the rough window frame opening you could also run into a problem where the original width interior trim molding may not be wide enough to reach the old interior drywall paint lines. If you have no choice but to buy the slightly smaller replacement window then you’ll need to consider using a wilder trim molding.

The size of the replacement window you purchase can also effect the work on the outside of the home. You may need to increase or decrease the width of the exterior window molding to butt up smoothly to the existing house siding.

How to Install a Window Ebook

If you need more help on choosing the right window replacement for your home, contact one of our pre-screened window installation contractors. They can help you select the replacement windows that are right for your home and budget, and perform the installation.

For more information on Installing Replacement Windows and Interior Window Trim

  • See the Installing a New Window Ebook from  The Installing a New Window Ebook provides easy to understand, step-by-step instructions, on how to remove an old window and install a new one. Pictures are included for every key step in the process.
  • See the Installing Interior Window Trim Ebook from  The Installing Interior Window Trim Ebook provides easy to understand, step-by-step instructions, on how to install interior window trim around a window. Pictures are included for every key step in the process.

Related Information

Additional Window Installation and Maintenance Resources from

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