Key Takeaways
- You can often fix a leaky window frame by caulking or installing weather stripping.
- Leaky window frames can be caused by poor installation, lack of maintenance, or structural shifts in the home’s foundation.
- To prevent future leaks, keep weep holes clean and perform regular home inspections.
You may have a window frame leak if your home feels damp or drafty, you’re seeing peeling paint or wallpaper around your windows, or condensation is pooling in the window frames. Depending on the cause of the leak, you may be able to repair it yourself through methods such as caulking or installing weather stripping.
Leaky window frames are often caused by improper installation. However, other culprits include deteriorating materials, foundation shifts, or clogged weep holes. If you’ve found excessive damage to your windows or have tried DIY methods with no luck, you may need new windows.
In this guide, we’ll cover how to find the source of the leak and how to repair or replace the seal. We’ll dig into what you can tackle on your own, and when it makes sense to call in a pro — or when it’s time to replace your window altogether.
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Why Your Windows Are Leaking
The first step in examining why your window frame is leaking is to determine whether you’re dealing with a leaking frame or a failure of the insulated glass unit (IGU) seal. It can be easy to confuse these two window components.
The table below can help you identify the type of leak you’re experiencing.
| Feature | Leaking Window Frame | Leaking Window Seal |
|---|---|---|
| Location of Leak | Around the edges of the window frame | Between the panes of glass |
| Cause | Installation issues, deteriorated caulking, structural shifts | Aging or damaged seals between panes |
| Symptoms | Water stains, peeling paint, soft wood | Condensation or fogging between panes |
| Solution | Recaulking, flashing repair, weep hole maintenance | Seal replacement or window replacement |
A leaking window frame could be caused by issues such as failed caulk or a settled foundation. We’ll examine potential culprits in detail below.
Poor Installation
Improper installation and the failure to create a tight seal are the primary causes of window leaks. Factors that can negatively impact window installation include misaligned flashing, inaccurate measurements, poor shimming, poorly installed house wrap, non-corrosion-resistant fasteners, and damage to the window itself before or during the install.
Deteriorated Caulking or Sealant
Using the right type of caulk or sealant, and keeping it in good condition, is paramount in preventing window frame leaks. Over time — and especially in extreme climates — caulk shrinks, cracks, and breaks down. This deterioration allows water to penetrate.
Make caulk inspection part of your routine home maintenance and look for cracks, gaps, and peeled caulk, all of which are signs of damage.
Clogged Weep Holes
Weep holes are strategically placed openings on the exterior side of the window frame on the bottom near the windowsill. They should never be caulked over or filled with debris. Though they are small, their role is important as they allow condensation and moisture to drain from the window, protecting the window and surrounding structure from water damage.
Damaged Weather stripping
Inspect your weather stripping around the window. Compromised weather stripping can let water seep in.
Structural Shifts
Soil erosion or wash away — or even settling or sinking ground — can cause your home’s foundation to shift. When that happens, walls and structural supports fall out of square, causing gaps between the window and the framed opening, creating a much larger problem than just a leaky window.
How To Find the Source of the Leak
You can take several steps on your own to try to pinpoint the source of a window leak. However, “You may need to bring in a variety of experts to track down a window leak,” said Bar Zakheim, CEO of Better Place Design & Build in San Diego. “You could be looking at problems related to roofing, siding, or the window itself.”
To give it the old DIY try, consider these options:
- Do a visual inspection. Look for cracks, gaps, deteriorated sealant, or clogged weep holes.
- Do a smoke test. After closing all windows and doors, and turning off any combustion appliances in your home, bring a lit candle or incense close to your window frame to see if there are changes in the smoke patterns. This works best on a windy day, or you can try turning on your bathroom and kitchen exhaust vents.
- Inspect for dampness. Peeling paint or wallpaper, water stains, mold, mildew, or warping on interior walls near windows are all signs of a moisture problem.
Conduct a water test. This test works best with two people. Have one person remain inside while the other sprays the window’s exterior with a garden hose, bottom to top. The person inside may be able to spot the leaks in action.
How To Fix a Leaking Window Frame
“Caulk is the quick-and-easy answer here,” Zakheim said, “but it’s important to make sure you aren’t caulking over a more serious problem that needs real repairs.”
If your visual inspection found the window caulk in need of replacement, here’s how you can fix it:
- Prepare the area: Using a utility scraper or putty knife, remove the old caulk/sealant and clean the area with rubbing alcohol for better adhesion.
- Recaulk: Using an exterior-grade caulk and a caulk gun, apply steady pressure along the seam and then smooth flat with a wet finger. Let it cure to seal. Wider gaps will need a foam backer rod installed before applying caulk.
- Check flashing: Ensure the window flashing is intact and directing water away from the window.
- Install or replace weather stripping: Add or replace weather stripping to seal windows even further. Most foam stripping is found at the top of the lower sash or where sashes meet. For easy installation, use the foam stripping with adhesive backing. Applying weather stripping will also increase your window’s energy efficiency.
Professional Window Repair
The cost of professional window repair or replacement may be worth it for the peace of mind it provides — especially if you’ve found damage to your flashing, or if you’ve done the steps above to reseal your window but the leak persists.
Buying new windows now will always be less expensive than dealing with rot, mold, and mildew later on.
If you’re unsure whether it’s your window frame leaking, it’s best to consult an expert. Leaks are sneaky and can masquerade as a different issue. “Some windows can also seem to be leaking when the issue is actually higher up on the house. Water might seep in through a bad upstairs window frame, then drip out of a first-floor one,” Zakheim said.
Cost To Fix a Leaking Window Frame
The cost to repair a leaky window varies depending on the specific repair required. Caulking and adding weather stripping is the least expensive option, with costs as low as a few dollars for a DIY repair on one window.
To replace a window, expect to pay a little more, as the national average cost to replace a window is between $400 and $1,000*, depending on the window’s size and frame material. Vinyl windows will be the least expensive, the easiest to source, and have decent energy-efficient qualities.
*Cost data is from RSMeans, a price estimator database for contractors.
Pro Vs. DIY
Most homeowners should be able to replace window caulk, sealants, and weather stripping. But when it comes to replacing cracked glass or the IGU seal, it’s best to consult a professional.
The same goes for the window flashing, and the waterproof barrier surrounding your window underneath the siding/trim. Issues related to a poor window installation and the surrounding area are more complicated to repair and should be evaluated by a pro.
Signs of Moisture Damage
If your window isn’t visibly leaking but you suspect a problem otherwise, it’s good to know the signs of moisture damage. If you see any of the following, call a professional for help:
- Discoloration or staining
- Mold or mildew
- Peeling or bubbling paint or wallpaper
- Swollen, soft, or crumbling wood
- Warping
Preventing Future Window Frame Leaks
Regular maintenance is key to preventing future window leaks. Not just for the window itself, but also for other parts of your home that protect the window. Incorporate the following actions into your regular home maintenance schedule:
- Clean windowsills and tracks regularly. Remove debris and wipe them down to clear condensation. This helps keep your windows and frame mold- and mildew-free, preventing rot.
- Ensure weep holes are free of debris at all times. Use a small, flathead screwdriver, or even a toothpick, to gently remove debris from the weep holes.
- Regular gutter and downspout maintenance is vital in diverting water away from your home. Directing water down and away from windows helps keep the area snug and dry.
- Roof overhangs are an important component in keeping water away from windows and siding. Ensure yours are in good repair, and vegetation isn’t touching.
- Conduct regular window inspections to catch problems quickly, before they multiply.
Next Steps
Windows play a critical role in keeping your home in good shape, though they’re only one component of your home’s exterior.
Think outside the box when it comes to protecting your window investment. By installing gutter guards, you reduce the need for gutter maintenance and the likelihood of water overflow and window leaks.
Keeping your bushes trimmed back away from your windows and siding helps control pests and prevents rot in your siding and trim.
If you’re seeing a lot of condensation around your windows, consider a whole-home humidity test. You may find the humidity level in your home is off and you don’t have a window leak issue at all.
If you find yourself outside your depth with any of this and need to consult a pro, consider getting multiple bids and perspectives on the repair.
FAQs About Fixing a Leaking Window Frame
What are common causes of window frame leaks?
The most common cause of a leaky window frame is poor installation. If the flashing wasn’t installed correctly or the window wasn’t sealed properly during construction, water can seep in during heavy rain. Other culprits include clogged weep holes (especially on vinyl windows), cracked caulk, worn-out weather stripping, or gaps where the siding meets the frame. In older homes, shifting foundations can also create gaps over time.
If you notice persistent moisture, call a pro to inspect — catching it early can prevent costly wood rot or mold behind the walls.
What should I do if my siding is soft and paint is bubbling around my window frame?
These are all signs of a leak, and it may not be from your window. It could be from the roof, the home’s second story, or a poorly sealed seam in the siding. The soft siding suggests wood rot underneath, and bubbling paint often means trapped moisture trying to escape.
Get a professional opinion to help pinpoint the source of the leak before the water damage gets worse. The longer you wait, the more damage you’ll face, including potential mold, insulation failure, and structural decay.
What type of caulk should I use to recaulk my window frame?
For outdoor window repairs, use high-quality exterior-grade silicone or polyurethane caulk. These are flexible, waterproof, and UV-resistant, meaning they won’t shrink, crack, or peel after a few seasons. Avoid latex caulk outdoors; it breaks down faster in the elements.
Make sure the surface is clean and dry before caulking, and check the temperature range on the label — most products need it to be at least 40 degrees Fahrenheit and dry for 24 hours to cure properly.
How do I know if I need new windows?
You likely need a window replacement if:
- The glass is cracked, foggy between panes, or no longer insulates well.
- The frame or sash is warped, soft, or rotting.
- The window sticks, won’t open, or won’t stay shut.
- The paint is peeling or bubbling, suggesting water intrusion.
If you’re seeing these issues, it’s often more cost-effective to replace the whole unit. New windows offer better energy efficiency, improved curb appeal, and fewer headaches.
Unless you’re experienced with window installation, it’s best to skip DIYing and consult a professional — especially if structural framing is involved or you’re seeing signs of water damage.
