How do you seal under a sliding glass door?

Having a properly sealed sliding glass door is important for energy efficiency, pest control, and preventing drafts. There are a few key areas that need to be sealed on a sliding glass door to prevent air leaks – the gap between the door panels and frame, the bottom track, and around the sides. Sealing these areas correctly takes some work, but it can be a DIY project if you have the right materials. In this article, we’ll walk through the steps for sealing under and around sliding glass doors using caulk and weatherstripping.

What Are the Benefits of a Tight Seal?

Sealing any leaks around sliding glass doors provides a few important benefits:

• Saves energy – When outdoor air can freely pass through gaps and cracks, your heating and cooling system has to work harder to maintain the indoor temperature. Sealing leaks makes your home more energy efficient.
• Reduces drafts – Gaps allow cold outdoor air to blow into the house, causing uncomfortable drafts. Sealing them up helps keep indoor air more stable.
• Keeps out pests – Rodents, stink bugs, spiders and other pests can enter through the smallest cracks and crevices. A tight seal leaves less opportunity for them to get inside.
• Lowers humidity and prevents moisture issues – Air leaks can increase indoor humidity levels and allow moisture to seep in, causing condensation and potential mold growth. A proper seal maintains a comfortable humidity level.

In general, a tight seal leads to a more comfortable, energy efficient, and pest-free home. It’s well worth the effort to seal any sliding glass doors thoroughly.

What Areas Need to Be Sealed?

There are four main areas around sliding glass doors that tend to cause air leaks:

1. Between the door panels – There is usually a vertical gap between the fixed panel and sliding panel. This gap needs to be sealed the entire height of the door.
2. Between door panel(s) and frame – More gaps exist along the sides where the panels slide back and forth within the frame. Sealing this gap all the way around prevents air passing through.
3. At the bottom track – The track that the sliding panel rolls back and forth on often has openings that let in drafts.
4. Around the side frames – Gaps can form between the side frames and wall framing, letting in outdoor air.

Focusing on thoroughly sealing these trouble spots will go a long way towards improving the door’s performance and comfort.

What Supplies Do You Need?

Sealing a sliding glass door requires just a few inexpensive materials:

Caulk	For filling larger gaps up to 1/2″ wide. Look for a quality acrylic or silicone caulk that stays flexible.
Weatherstripping	Used for sealing smaller cracks. Foam and felt options are available.
Drop cloth	Protects flooring from caulk drips.
Paper towels	For cleaning up excess caulk.
Paint scraper	For smoothing caulk.
Tape measure	To measure for weatherstripping length.
Utility knife	For cutting weatherstripping.

You may also need a caulk gun, ladder or step stool depending on the door’s height. Make sure to get the right supplies before beginning work.

How to Caulk Between Door Panels

The vertical gap between the fixed and sliding door panels can let in a surprising amount of air. Use the following steps to caulk this gap:

1. Clean the gap thoroughly so the caulk adheres. Vacuum out any dirt or debris.
2. Place a drop cloth on the floor below the gap to catch any drips.
3. Load the caulk gun with a quality acrylic or silicone caulk. Cut the tip at a 45 degree angle for easier application.
4. Run a smooth 1/4″ bead of caulk the entire height of the gap between the panels. Don’t leave any areas unsealed.
5. Use a paint scraper or your finger to smooth the caulk and remove any excess immediately. Wipe hands on a paper towel.
6. Allow the caulk to fully cure for at least 24 hours before closing the door panels.

Take care not to use too much caulk or it will ooze out. A thin bead is all that’s needed to create an effective seal.

How to Caulk Around the Frame

Gaps between the door panels and frame are also common culprits for air leaks. Follow these steps to caulk around the perimeter:

1. Check for any existing old caulk or gaps wider than 1/4″ and use a utility knife to cut these out. Wipe away debris.
2. Run a steady 1/4″ bead of caulk in the gap between the frame and door panel all the way around the perimeter. Don’t skip spots.
3. Use a scraper and paper towels to smooth the caulk into the gaps and remove excess before it dries.
4. Make sure the caulk forms an airtight seal with no pinholes or cracks.
5. Let the caulk fully cure before moving the sliding panel again.

Take time to neatly apply the caulk around the entire door frame for maximum results.

How to Weatherstrip the Bottom

The bottom of the door where the sliding panel rolls back and forth deserves special attention. Weatherstripping will seal this area nicely:

1. Clean the bottom track thoroughly and vacuum out any debris.
2. Measure the length of the track area.
3. Cut a piece of foam weatherstripping slightly longer than the opening.
4. Peel off the backing paper and press the weatherstripping into place along the bottom.
5. Use scissors to trim off any excess material.
6. Make sure the weatherstripping sits squarely in the track so it seals thoroughly when the door closes.

Compressible foam weatherstripping blocks drafts while still allowing the sliding panel to move freely. Replace it whenever it becomes worn or compressed.

How to Weatherstrip the Side Frames

The left and right side door frames also need weatherstripping to block wind and debris. Here’s the quick process:

1. Thoroughly clean the side frames with a vacuum and rag.
2. Measure the frame height and cut a piece of weatherstripping to match.
3. Remove the adhesive backing and press the weatherstripping tightly into the side frame groove from top to bottom.
4. Use a utility knife to trim off any excess material.
5. Make sure it fits snugly with no gaps or wrinkles.
6. Repeat on the opposite side frame.

This seals off the side frames nicely to prevent indoor air from leaking outside. Replace the weatherstripping if it becomes loose or damaged over time.

Maintenance Tips

To keep your sliding glass door seals in top shape, remember these maintenance tips:

• Check the seals twice a year and re-apply caulk or weatherstripping as needed.
• Keep sliding tracks clean from dirt and debris, which can degrade seals over time.
• Reseal any areas that lose adhesion or appear gap-ridden.
• Look for signs of pests or moisture and immediately reseal any access points.
• Replace weatherstripping along the bottom every 2-3 years as it naturally compresses.

With regular inspection and upkeep, your seals should hold up nicely for many years before needing full replacement again.

Conclusion

Sealing a sliding glass door effectively comes down to caulking between the door panels and frame, adding weatherstripping along the bottom track and side frames, and performing regular maintenance. While it takes some time and handywork, the energy savings, comfort, and durability are well worth the investment. With the right materials and these step-by-step instructions, you can stop drafts and pests from sneaking through your sliding door once and for all.