How to Replace a Windowsill
If your windowsill is rotting, you need to act before the rest of the rot attacks the window. Here are the steps to a secure windowsill replacement in about half a day.
Your Replacement Tools
- Safety gloves
- Safety goggles
- Utility/putty knife
- Reciprocating saw
- Pry bar
- Table saw
- Wood hardener
- 1″ Stainless steel nails
- 100-grit sandpaper
- Measuring pencil
1. Remove windows and shutters before starting work.
Remove anything that could be a working hazard so you get a secure work environment. This will also prevent damage to the windows in case something goes wrong during removal.
2. Get rid of any caulk, paint, or nails connecting the sill to the window
You can use a utility knife to pry these loose. Make sure you address the seals of paint, caulk, and nails on all four sides. If you do not get rid of the caulk, paint, or nails, it could damage the rest of the window, forcing you to replace your window. Problematic nails may need to be removed with pliers.
3. Remove the window trim
Instead of contending with confined cuts, remove the trim. This keeps the trim safe and prevents you from investing more time and money on repairs.
4. Cut the window sill in the middle
A reciprocating saw is suggested for this task. Cutting in the middle will allow for easier leverage upon removal.
5. Hammer the bottom of the window sill up
This will jar it loose and allow for easy removal of the two pieces. Once the two are loose, you should be able to pull the sill out easily. If you cannot find an exact duplicate for sale, use a non-damaged section of the original as a template for the replacement.
Note: When choosing or making a replacement, make sure the new model is several millimeters larger than the original. Wood condenses over time due to moisture and the elements. It is crucial to make the seal between the window as tight as possible to the house without overdoing it. Use your discretion when upgrading.
6. Prep the replacement for installation
Measurements for your new window sill should be exactly the same as the old one. This includes length, thickness, slopes, and even any ears, or notches, that were on the previous model. Creating a new piece will involve a table saw and protractor so you can get the exact measurements needed for your house.
You can prevent future rot by applying wood hardener at the ends of your new piece. Wood hardener makes the interior of the wood denser, preventing moisture from seeping in.
Also, apply primer to the sill before installation. You will want to paint it whenever it is installed so you can match the window’s colors. Make sure primer is applied in a secure environment so you can control application before subjecting it to the weather.
7. Before installation, sand and tape the affected area
Removing the rotted wood could have revealed or even caused damage to the existing area. Sand down any jagged edges using 100-grit sandpaper. Also, apply wood hardener where needed.
8. Slide your new sill in and secure it
All the prep work you have done so far should let you slide the sill in with ease. Secure it with waterproof caulk and 1″ rustproof stainless steel nails. When you have done this, use waterproof paint on the entire area to match.
If you do not get a fit, recut and remeasure until you successfully replace it. It may take several tries, but make sure it is secure while also fitting to the house.
If you still have questions about replacing a window sill, along with any other questions about window replacement or even radiant barrier, contact the team at Green Energy of San Antonio. We’re ready to help you with any window problems you have today.