How to Caulk Windows

How to choose the right type of caulk

As you examine your home, check the caulking on the inside and the outside of the window. The location determines what type of caulk you’ll need.

Here are a few types to choose from. Some are more resistant to moisture, making them suitable for sealing outdoors. Others might break down faster if exposed to water, but expand better and can be painted. So be sure to choose the right caulk for the job.

Here are a few examples to consider:

Silicone caulk (indoor/outdoor use)

Pros

• Durable;
• Water resistant;
• Weatherproof;
• Mold resistant;
• Top choice for outdoor surfaces.

Cons

• Some types can’t be painted; check the label.
• Doesn’t adhere to every surface.

Polyurethane caulk (outdoor only)

Pros

• Adheres to all types of materials;
• Paintable.

Cons

• Breaks down when exposed to sunlight; paint over it so it lasts longer.

Siliconized latex caulk (indoor/outdoor)

Pros

• Can be painted;
• Works well in humid rooms;
• Flexible with temperature changes.

Cons

• Can be damaged if constantly exposed to rough weather.

Acrylic latex caulk (indoor)

Pros

• Durable;
• Low odor;
• Cleans up with water;
• Expands into the seam;
• Paintable, or comes in various colors.

Cons

• Not weather resistant.

Caulking guns

The smooth rod caulk gun will be your new best friend, making applying caulk easy peasy. A midrange gun should be fine. Unless it’s a major project, you probably don’t need a high end electric model. But don’t go with a cheap one that might break before you finish your project.

Now that you have your caulk and gun, let’s get started!

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How to remove old caulk

If you’re dealing with moldy, old, or deteriorating exterior caulk, be sure to remove ALL of it before applying new caulk.

• Scrape off the old caulk with a utility knife, putty knife or a caulk removal tool.
• Clean the surface with rubbing alcohol.
• Let that surface dry completely. If any moisture remains, mold could form under the new caulk.

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Prep the surface

• If indoors, apply painter’s tape above and below where the caulk will go. That creates a clean line so you apply the caulk exactly where you should.

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Open caulk tube

• If your project requires thin lines, use a scissors or utility knife to cut the tip off the caulking tube at a 45-degree angle.
• For fatter lines, cut the nozzle closer to the tube.
  • Pro tip: There’s a hole in the gun on the side to snip off the tip, but it can be tricky to use. Only do it if you need a larger line and don’t mind cutting off a bit more.
• Finally, use the thin metal rod attached to the caulk gun to pierce the inner seal. If there isn’t one, a nail works fine.

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Load caulk gun

• Typically, smooth rod caulk guns have a metal trigger on the back. While pressing it down, pull back the L shaped rod (rotated to point down) as far as you can.
• Insert the tube by placing the nozzle into the hole at the face of the gun, then pressing the flat base of the tube to the back of the gun.
• Pull the trigger until the base plate of the rod is firmly against tube.

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Test your skill

• Practice using the caulk gun on a piece of paper or cardboard.
• Squeeze the trigger, moving down the line at a 45-degree angle and a consistent pace. If you go too slowly, the caulk might clump up. Too fast, and areas might not be covered.
• Make sure to bend at the elbow and keep your wrist steady.
• Start away from your body and draw the line of caulk towards you.
• If the line is too small, cut it again.

Once you have the hang of it, go ahead and start caulking!

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Caulk window

• Make sure to point the tip towards the seam.
• Don’t make the common caulking mistake of trying to run a continuous bead from corner to corner. Start away from your body at the farthest corner and move the line toward you.
• Once you reach the middle of the window, stop and turn around to the other side. Start at the other corner and pull the line towards your body again to meet the already created line in the middle.
• Remember to bend at your elbows and keep your wrist steady.
• Do this for all four sides.

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Finishing step

• For a beautiful finish, dip your finger in water and run it over the caulk.
• This will also push the caulk into the joint and make sure the seal is tight and smooth.
• When finished, wipe the caulk off your finger with the wet rag.

Pro tip: Start running your finger ahead of the caulk a bit, then keep going. This will keep the line smooth from start to finish.

If the caulk ever becomes too thick at one point, run a wet finger through the line to remove the excess. If you don’t, that edge or bump will show up when you paint over it.

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Let it dry

• Remove the painter’s tape.
• Check the recommended drying time on the caulking tube, then let it dry.

Fantastic! Now your window is prepped for all kinds of weather.

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