Where Do I Need to Caulk Windows?

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When it comes to window caulking, the more you seal the better, right? After all, closing off gaps and replacing old caulk prevents prying winds and rain from entering your home, which keeps you snug and dry. While that’s true in theory, it’s not necessary to plug every joint on your window frames—particularly between the glass panes on a replacement window.

It comes down to an issue of design—the type of window and siding material, as well as whether the frame is new or replacing a previous window. Furthermore, there’s an aesthetic benefit to caulking the interior glass—a pretty compelling argument for many homeowners.

Keep in mind that there are plenty of spots you’ll want to avoid caulking altogether, depending on the type of window frame you have and how it fits against your siding. Here are the dos and don’ts of caulking for your windows.

Sealing Window Leaks

Caulking Window Interiors for Aesthetics

Caulking is generally only necessary on the exterior of your windows—unless you have noticeable interior gaps, in which case you should seal up where the trim meets the wall and window.

For most homeowners, caulking windows between glass panes is something done merely for aesthetic purposes. The window caulk between the glass and the frames gives them the finished look that we’re used to seeing, but it doesn’t do much to prevent drafts or keep out the wind and the rain. However, since windows fit tightly together, moisture and air leaks between the glass isn’t necessarily a problem. If you’re interested in achieving this aesthetic, use acrylic latex painter’s caulk. If your taste is more clean and modern, go ahead and leave them uncaulked.

Special Concerns for Replacement Windows

Replacement windows are typically well-sealed in the interior, so caulking there is often optional. Where you do need to pay attention to sealant is around the frame, where the window fits into the wall opening. Windows typically come in standard sizes, since the opening was cut to another model, but sealing those gaps with expanding foam is vital to your home’s comfort and energy consumption.

When Should I Caulk Between the Frame and Window Panes?

The question of where and how to caulk windows depends a lot on the kind of siding and frames you choose to install.

Do you have vinyl frames? These tend to hold the glass more tightly than say, wood frames do. Therefore, if you have vinyl frames going into a home with vinyl siding, you may only need a little painter’s caulk applied to the edges where the glass meets the frame.

Use 100% silicone caulk—it’s waterproof, durable, and flexible. It won’t freeze in the winter or deteriorate in high heat, and it will last 20+ years. The only downsides are that silicone caulk doesn’t adhere well to wood and it can’t be painted. Siliconized latex caulk is a resilient and paintable alternative.

Do you have wood siding? If your home is clad in wood siding and you’re installing wood framed windows, you may need to do a little more work to prevent leaks and moisture infiltration. Because silicone caulk doesn’t seal as well to wood, you’ll need to securely seal all the gaps using clear polyurethane caulk rated for exterior use.

Polyurethane caulk will last between 10-20 years, and because it’s not a UV-resistant material, it should be painted over to avoid sun deterioration.


Places Where You Should Not Caulk Your Windows

Don’t get too crazy with that caulking gun because there are definitely some places around your windows where caulk should never go. While it may be tempting to seal up any and all gaps you see around your windows, some of them may be necessary to vent excess moisture from behind your window trim. Here are some places to avoid  (or be careful about) caulking:

  • The window’s weep hole: This small hole at the bottom of the exterior frame in vinyl windows allows moisture behind the window to exit through the frame. If you plug this hole, you could cause mold or rot to grow unchecked.
  • Moveable parts: The last thing you want to do is seal your windows closed! Avoid operable parts, like sashes in a double hung window, for example.
  • If your windows are trimmed out so that the trim sits above the siding: This is common in many modern homes, where the cladding is carried out to the edge of the window frame. In this situation, it isn’t necessary to seal the joints. In fact, it will harm your windows, since this acts as a channel to carry excess moisture away from your siding and windows.
  • Where the window trim meets the siding: Many homeowners are confused about whether or not they should seal the joints here. The best answer is “it depends.” If the trim sits flush against the siding, then yes, by all means, it should be properly sealed. Caulking these joints with weather-proof silicone caulk keeps moisture from getting behind your siding, which can cause all kinds of havoc with your home’s interior walls.
  • Above the window frame: This is a spot to avoid, no matter what kind of window you have installed. This spot is known as a drip edge, and its job is to carry rain and snow away from the windows and siding. If you close off this joint with caulk, it can cause moisture to become trapped behind the frame and the edge of the siding. Again, that often spells big trouble for your home’s exterior walls and your window frames down the line. So do yourself a favor and keep this spot seal-free. You’ll thank yourself every time it rains.

Here are some other helpful pages to help you through your replacement window project.

Best Window Brands 

Cost for Window Replacement

Measuring Replacement Windows 

Standard Window Sizes

Types of Window Frames

When to Replace Windows 

Window Glass Repairs 

Window Rebates & Incentives 

Window Replacement Information

Window Replacement Contractors Near Me



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