Window Leaks From Top When It Rains – What To Do?

Did you notice leaks from the top of your window whenever it rains, and you want to know how to best take care of the problem? You’ve come to the right place, for we have researched this question, and we have the answer for you.

There are several reasons why a window will leak. Here are the most common issues:

  • There is a problem with the overhang
  • There is a gap or damage in the wall siding
  • Poorly maintained window frame and window drip cap
  • Condensation

We will discuss these causes in the succeeding sections so that you will have an idea of what to do to address the issue. Read on!

Freezing and the formation of condensation and mold on the new plastic window, Window Leaks From Top When It Rains - What To Do?

How to fix problems with the overhang?

A study in 1996 in Canada showed that up to 90% of low-rise residential buildings in the study that didn’t have any roof overhang also had water problems. On the other hand, only 20% of the same type of buildings had water problems if they had a roof overhang of 24 inches or more. The result of the study showed that water problems decreased as the size of the roof overhang increased.

If we analyze roof overhangs, any rainwater that gets to the roof and overhang will fall to the ground before it can reach the wall or the window frame. Overhangs keep rainwater away from windows and walls.

Thus, if your house has an overhang and you’re still getting a leaky window, then you need to check the overhang for design problems.

Faulty fascia

One of the functions of a fascia is to divert water away from your windows and walls. If the fascia on your overhang is slightly angled inward, then the rainwater flowing down the fascia would flow towards the house instead of away from the house.

If you have an older house, your fascia might have warped after years of getting exposed to the elements. Some of the warped sections of the fascia might have started to angle towards the walls and windows of your house, and this is causing the leaks in your window.

If your window was designed to be protected by the overhang in your roof, it might not be sealed properly against rainwater. Thus, the water that gets to your window from the fascia is causing leaks.

How to fix the issue?

This problem is best handled by a professional. They will check your fascia for any warping and replace it as necessary.

As an option, you can have your window and wall sealed properly so that any similar incident in the future will no longer cause leaks.

How to fix issues with the wall cladding?

Wall construction with insulating wood cladding in countryard

The siding or wall cladding is any material that provides protective skin to the outer wall of a house or building. It is used to provide the outer wall with a certain level of thermal insulation from environmental temperatures and weather resistance.

The siding and the roof are a house’s first line of defense against the elements. However, the siding also serves the third function of improving the appearance of the wall structure.

Siding is often made of weather-resistant materials like shingles, clapboards, fiber cement, slate, stone, vinyl, and brick.

The siding protects the wall under it. Thus, if there is a gap or damage on the siding, then water will be able to penetrate through and cause a leak.

If the siding at the top of a window is damaged, cracked, or falling apart, then it could lead to a leak in your window. This is highly likely if the damage is above the window drip caps. The water that bypasses the siding will be able to get under the window drip cap and cause a leak.

How to patch and repair siding?

The exact repair steps will depend on the type of siding. There are types of siding that are easy to repair, while some will require a professional.

Some homeowners consider the difficulty in repairing the siding when they choose their siding. Thus, vinyl is one of the common sidings that you would see.

Here are the steps to repair two common types of sidings:

Vinyl sidings

Window in the wall of brown vinyl siding

Vinyl siding is the easiest to repair and patch because they are pre-molded. To replace a damaged siding, simply remove the entire damaged panel and replace it with a new panel of the same size and color.

However, if you just need a quick and temporary repair of the damage, you can patch it in 15 minutes or less. Follow the simple steps below to patch a vinyl siding.

  1. Measure the size of the damaged part plus 4 to 6 inches on both sides.
  2. Cut a piece of the same type of vinyl siding using a sharp cutting knife.
  3. Use a cutting knife to score the hem on top.
  4. Push the hem away from the vinyl siding, and it will snap off.
  5. Rest the vinyl siding vertically on a hard surface.
  6. Score the butt lock at the bottom.
  7. Snap the butt lock off.
  8. Slide the piece of siding over the damage in the siding.
  9. Drill a small hole for the rivet at the bottom. The holes should be an inch away from the edge on each side.
  10. Use a pop rivet tool to insert a rivet (preferably with a matching color) into the vinyl siding.

Clapboard siding

Grey clapboard siding house wall with windows

Clapboard siding can rot when water finds its way into the seams of the wood. This happens when two or more seams are on top of each other.

Follow the simple steps below to replace a rotten clapboard siding.

  1. Mark the clapboards that you will replace.
  2. Use a sharp knife to run under the boards to remove the caulk. You need to cut the caulk before pulling the clapboard so that the other clapboards will not crack.
  3. Pull the clapboard above the one that you are going to replace. Insert a flat bar into the clapboard and gently pull it up to make room for the one that you need to remove.
  4. If the board that you need to remove is too long and you only have a little damage on one section, you can cut that part with a saw.
  5. Measure the length of the clapboard that you need to replace and trim the replacement board to match your measurements.
  6. Slide the replacement siding into place.
  7. Use small mounting nails to fasten it into position.
  8. Nail the other surrounding boards that you loosened to get the damaged siding.

How to fix poorly maintained windows?

Windows need maintenance too. Caulk can dry up and crack. Cracked window sealants can lead to leaks.

Windows also have components that keep water away, like the window drip cap that we mentioned earlier. If the window drip cap is damaged—or if your window doesn’t have one—then water can get through and cause a leak.

What is a drip cap?

A drip cap is an L-shaped type of flashing that is installed on windows and doors. It is installed under the siding. The siding system protects the top of the drip cap.

The horizontal leg of the drip cap is installed over the window, and the vertical leg goes under the siding. Rainwater that goes down the siding is diverted away from the window by the drip cap.

However—like all flashing—a drip cap is made of metal, and one that is made of steel can rust over time. A rusted drip cap will no longer be effective in diverting water away from the window. Fortunately, you can replace them.

Use the techniques that we used earlier to replace the clapboard siding to temporarily raise the siding above your window. This will allow you to properly inspect the drip cap and the extent of the damage. Then follow the rest of the steps below.

  1. Remove the old drip cap.
  2. Clean the area thoroughly.
  3. Apply denatured alcohol on a clean rag and wipe the area with it. This will get rid of any mold in the area. Let it dry.
  4. Apply caulk if you need to.
  5. Let it cure.
  6. Install a new drip cap.
  7. Reinstall the siding over the drip cap.

Check the caulk

Another line of protection against leaks is the caulk seal around your window. Unfortunately, caulk can dry once it ages, and water can get through the cracks of a dry caulk.

Hence, one important window maintenance is the annual checking of window caulk and seals. This will allow you to find out if any of the caulk around your windows requires repair or replacement.

Window Condensation Issues

Drops of condensate and black mold on a substandard metal-plastic window

There are times when the leak on your window is not a leak at all but condensation. This is especially true if you experience a leak on your window even when there is no rain.

Condensation can build up on your windows when the warm air inside your house meets the cold air outside. Poor insulation is the common cause of this problem.

If you’re using a double-pane window and there is a leak in the seal, the argon between the panes will escape. The insulation of your window drops as more argon escapes, causing condensation buildup.

Window condensation is best handled by a professional so that they can trace the source accurately and fix the problem from there.


There are several reasons why a window would leak. Check all the possible causes to find the true cause of the leak.

If you enjoyed reading this article, you might find the articles below equally enjoyable to read:

How To Lubricate Casement Windows [And How Often To Do So]?

How To Fix A Cracked Window On Your House?

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