Add a Window to Your Home: Tips and Mistakes to Avoid

If you would like to add a window to an exterior wall on your home, there are a number of common mistakes you should take care to avoid. Making an error with the installation of a new window can cause all sorts of problems in the future so it's recommended that you take a little time to learn some of the tips for successful installation in the article below.

Window Opening Size

When you cut the hole in the exterior wall for the window, you should make sure that there is a half inch gap between the opening and the frame of the window you install. This gap is necessary so adjustments can be made during the fitting process to ensure that the window is plumb level to promote effective operation. Cutting the hole to the precise measurements of the window leaves no space for adjustment and is a common mistake made by someone installing their first window.

Leveling Window

One of the most important and time-consuming aspects of installing a new window is making sure that it sits absolutely level. When creating the window opening you should make sure that the bottom sill is level and use shims to adjust it if necessary. Hold the shims securely in position with nails, drilling a pilot hole initially to prevent them from splitting. After positioning the window, double check that it is level and make any necessary adjustments using additional shims before securing it in position.


The gap between the rough opening that you cut into your wall and the new window should be filled with insulation to prevent drafts coming into your home. Installing an energy-efficient window is completely pointless if it isn't properly sealed and insulated. Using suitable insulation will help to keep the window performing at the optimum level and save you money on your utility bills.

Moisture Seal

Using a moisture seal is just as important as insulating the gap around the window. Don't skimp on the width of the weatherproof strip. A strip of around 8 inches wide will cover the internal frame of the window sufficiently and save you the hassle of water ingress that can cause mold and mildew to form. Staple the weatherproof strip into place inside the window frame before installing the window.


It is easiest to install a window from the outside but many styles can be installed from within the house if necessary. Position the window then open it and lean through to fasten it into position. If you decide to use this installation method, you should take safety precautions and ensure that you are securely anchored before leaning out. Although this process is possible, it can be quite awkward so it is recommended that you install a window from the exterior side wherever possible. Many tool or rental companies offer daily rental of small cherry-picker machines that provide a secure position when installing windows on upper levels.