A Quick Guide to Caulking Your Windows

At Metro Sealant, we’re here to supply the very best in products and support, no matter your sealing needs.  This covers everything from high-end construction projects to basic DIY jobs you might want to do in your own home – such as caulking your windows.

Having properly caulked windows is important for reducing your energy costs, as well as helping ensure your home’s air conditioning is fully effective.  Windows with broken or missing caulk will have poor seals, allowing air to escape your home.  Fortunately, caulking is an easy process that just about everyone can do for themselves!

In this guide, we’ll tell you everything you need to know to do basic caulking – and with style.

I. What You Need to Caulk A Window

You only need a few basic tools to successfully caulk a window.

• A caulking gun (preferably with a thumb “trigger”)
• One or more tubes of caulk
• Painter’s tape, or masking tape as an alternative
• A small utility knife or putty knife
• Rags or paper towels
• A popsicle stick or similar flat/rounded tool
• Rubbing alcohol
• Sponge
• Hairdryer (optional)

Most of these are completely straightforward.  The only major question is what kind of caulk you should buy.  There are three basic options, depending on your needs:

Siliconized latex caulk is more commonly used in rooms such as bathrooms, but if you have some laying around, it can be used for windows as well.  Siliconized latex caulk can be painted over – important for doing windows – and resists moisture well.

Polyurethane caulk is usually the strongest and most durable option, but it’s also the most expensive – and possibly overkill for a simple home DIY project.  If you choose polyurethane caulk for a window seal, you must paint over it, because the basic caulk is vulnerable to UV light without a layer of protection.  If you’re planning on caulking several windows, this will probably be too expensive.

Silicone caulk such as Pecora 864 is probably your best option in terms of price vs performance, and the type of caulk we most often recommend for these types of jobs.   It has excellent water resistance, and bonds well to most materials.  Be aware when buying, some types of silicone caulk cannot be painted over, but usually come in a variety of colors so you can match your paint.

Also, we recommend avoiding acrylic latex caulks when sealing a window.  These caulks create a fairly weak bond, and do not stand up well to weather, so they aren’t a good choice for windows.

II. The Caulking Process

Once you have your tools and materials ready, it’s time to start the sealing job!

1.  Watch the weather

You want to do your caulking on a relatively warm day, at least 45 °F (7 °C) at an absolute minimum.  Any colder than that and the caulk may not set.  In general, hotter is better, since that will slightly speed up the rate at which the caulk sets – but it will still take around 24 hours to fully dry in any case.

Be sure to take note of the forecast – a rainstorm while the caulk is wet could easily destroy your work.  So pick a time when rain isn’t expected for a couple of days.  If possible, humidity should be low as well.  Extra moisture in the air will only delay drying.

2. Prepare the area to be caulked

This is a multi-part process:

First, remove any old caulk, using a utility knife or some other blade.  You must remove ALL of the old caulk, including residue, or else it could prevent the new caulk from forming a tight bond.  Be diligent!

Once the old caulk is removed, inspect the area for damage.  This is particularly important for wooden frames.  If there are signs of wood damage, such as rot, fix it before attempting to caulk!  Otherwise, the rot will continue to spread underneath the caulk.

If the surface looks good, it needs to be cleaned with water and rubbing alcohol, using a sponge to protect the material.  Get it as clean as you can, since dirt and debris will prevent the caulk from setting firmly.  Once it’s clean, it must be completely dry before caulking.  A hairdryer can come in handy here for speeding up the process.

Finally, apply the painter’s tape or masking tape just above and below the areas you’ll be caulking, to protect the rest of the window from damage.  Only the seam should be exposed.

Now you’re ready to caulk!

3. Prepare your caulking gun

Insert the tube of caulk into the gun while the tube is still sealed.  You’ll probably need to pull a handle back to make room for it, and the handle will lock into place when it’s ready for the tube.  The exact procedure here will vary slightly depending on the type of gun you have, but it’s similar for all models.

Once the gun is ready to go, it’s time to snip the tip off the caulk tube.  Do this at a 45-degree angle, which makes it easier to aim the flow of caulk.  Also, don’t cut the tip off too low down – a large hole will cause too much caulk to flow, creating a messy job.

4. Applying the caulk

Start at one corner of the window, pressing the tip of the caulk gun firmly into the gap.  You want to apply even pressure to the caulk tube so that the flow of caulk is regular.  Then apply the caulk to the seam in a single smooth movement.  Use both hands, with one near the tip, so you have better control of the caulk gun.  If possible, you want a single uninterrupted line of caulk for best results.

Then do the same for the other three seams.

If you have caulk leftover, point the gun upwards and give it a slight squeeze so that a bead of caulk covers the hole.  This effectively seals the tube and lets you use the rest at a later date.

5. Smooth the caulk

Take out your popsicle stick, or whatever you’ve found for this job, and run it along the caulk lines you’ve made.  You want them to look smooth, and indented slightly while removing any excess caulk. If you’ve got nothing else available, you can even use your finger for this.

For the sides of the window, make sure to smooth it from top to bottom so the excess caulk accumulates at the bottom for easy removal.

6. Wait a day

Don’t do anything once the caulk is applied.  As mentioned above, it will take at least 24 hours for the caulk to fully set.  If it becomes humid or a light rain happens, give it even longer.

7. Finish up

Finally, once the caulk is fully set, you can finish up the job by removing the tape you laid down on either side of the seam.  In addition, this is when you can paint over the caulk if the caulk is paintable and you want to match it to your house.

Get Silicone Caulking Products Like Pecora 890 and Pecora 864 Today

Metro Sealant has a wide variety of caulks available, and the expertise to match!  If you need any help with your window caulking, just contact us.