How to Apply Silicone Rubber Sealant to Windows

A worker caulking around the edge of a window.
  • 2-4 hours
  • Beginner
  • 0-100
What You'll Need
Silicone rubber sealant
Caulking gun
Masking tape
Soapy water
Utility knife

Silicone rubber sealant is an excellent way to stop drafts from entering around windows. This not only keeps your home warmer, but also cuts down on your energy bills. There is a proper way of applying silicone rubber sealant so it does its job properly and still looks good. It’s not especially difficult but like anything else, the technique does have to be learned and mastered.

Step 1 - Find Where to Apply

The first thing is to know where to apply the silicone rubber sealant. Because it works as a draft excluder, you have to be aware of where there are drafts around your window. The best way to discover this is by holding a lit candle close to the window frame and seeing where the flame flickers, as this will indicate an area in need of repair. You’ll need to apply a bread of silicone rubber sealant all along an area, not just on a single spot.

Step 2 - Prepare the Area

To ensure you apply an even bead of sealant, use masking tape to form edges. Put a single long strip on either side of the joint where you’ll be applying the caulking. This will keep the sides neat on the window frame.

Now, take your tube of silicone and place it in a caulking gun. It will have a spout that you'll need to cut at a 45-degree angle in order to get the smoothest bead out of the tube.

Step 3 - Apply

You need to squeeze out a smooth, even bead of silicone rubber sealant along the window. This can be the trickiest part of the process, and it’s worthwhile taking time to practice in order to master it. You don’t need to squeeze hard; just keep up a low, even pressure and run the tube along between the pieces of masking tape.

Don’t try and run sealant around the entire window in one go. It’s much better to do one side at a time, as this means you’ll be able to work without risking the silicone drying out, and you won’t feel under any pressure to rush.

Step 4 - Smooth

Once you have the bead of sealant on the window, you need to smooth it out. Plenty of people have problems with this, but it’s not especially difficult. Dip your index finger in soapy water and run it along the bead. Ideally, you should be able to go all along in a single motion but that won’t always be possible. If multiple strokes are needed, try to use as few as possible and always go in the same direction. The idea is to make the line look completely smooth. Where different sides of the frame meet, smooth down the joint with your fingertip.

Step 5 - Finish

When you’ve finished smoothing the sealant, leave it to dry completely, and then pull off the masking tape. This should remove any uneven edges, but if any remain, even them up with a razor blade or utility knife.

With that, any problems with a drafty window should vanish! Don't worry if your first attempt at applying sealant doesn't turn out perfect. Just remove it and try again until you're satisfied with the look.