Replacement Window Installation Instructions

Replacement window installation is not a particularly difficult process, but it does require some time and ability to finish to a satisfactory level. You should be prepared to replace your entire home after doing some research. Many households spend several thousand dollars installing their windows, but you can do it for as low as $300. The exact cost will depend on the number, size, and style of windows you choose to install. As expected, the cost to install bay or bow windows is more than that of a standard window.

The procedure for installing new windows consists of four key stages:

Collecting All Necessary Equipment
Taking precise measurements for the new window
Taking off the old panes of glass
Putting in new window panes in an existing frame.

The replacement of a large window can take up to four hours, and you’ll need various tools to accomplish the task. Tools including hammers, screwdrivers, chisels, knives, tape measures, squares, wood shims, wood putty, caulking tubes, sandpaper, expanding foam, and pry bars can usually be found around the house. Gather all the necessary equipment for the installation before beginning any measuring.

Sizing It Up

The fundamentals of window measurement are consistent across all measurement systems. Everything else you do will be based on how well this is executed.

You will need three horizontal and three vertical measurements to complete the measuring process. The measurements for height and breadth are taken from the inside edge of the window frame or the window jamb. Taking three measures along the horizontal and vertical axes is crucial. They would measure height at the left, center, and right. If you find that some of the dimensions are different from the others, the height and width you choose for your new window should reflect the smallest of these differences.


The window stops, or the pieces of the window frame that keep the pane in place will be the first to go. It may be as simple as unscrewing older windows or cutting the edges off with a tool knife and pulling them out. It’s best to save the window stops for future use and cost savings.

After taking out the window stops, the following step is to take out the window sashes or the window panel, depending on the type of window that is currently set up. The stops on either side of the window ensure that the strap or pane can be easily removed.

Last but not least, remove any separating beads that may be in the way of entirely removing the window sash; this step is usually unnecessary with casement windows. With the old window removed, you may prepare the window jambs for the new ones by filling any holes and sanding them down.


The replacement window installation is the last and most challenging step. The first step is to caulk the inside of the exterior stops, where the new windows will rest when installed. The window header is the first component to install and goes into the top jamb.

The next step is to test whether or not the square hole can accommodate the replacement window. If the window is too narrow for the opening, wood shims must be tapped into place to ensure a snug fit. You can secure the window by screwing it to the jamb when it is positioned correctly.

You can now test if your new window functions correctly by opening and shutting the significant sections and ensuring any movable components are adequately secured.

To learn more about how to measure for new windows and install replacement windows from an industry expert, visit James Preston’s DIY website.

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