How to Replace a Windowsill

Apr 14,2026

All windows have a windowsill. Over time, this part may weather, decay, or be damaged. Further, you may wish to alter the width of the sill or stool to better match the style of your home.

Windowsills and stools should always be replaced by a skilled professional—this will ensure your window maintains its functionality.

During windowsill replacement, a reputable service professional will:

Inspect the window. Your service professional will carefully inspect the window for signs of damage to parts outside of the sill or stool. If damage is detected, we’ll walk you through your options for a more extensive repair or a total replacement.
Prepare the space. Before construction begins, your service professional will remove the trim and any hardware that may impede the replacement.
Remove the existing sill. We will carefully remove the existing sill.
Measure and design. Understanding the structural importance of the sill and your design goals, your service professional will use either a pre-cut sill or cut a custom sill to install.
Install the windowsill. We’ll carefully install the new sill, ensuring that it’s level and secure.
Add the finishing touches. Now that your windowsill is fixed in place, all that’s left is caulking any cracks and sanding any rough edges.

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