How to stop roof water from overflowing and rotting the window sill
Water overflowing from the roof runs behind the gutter and lands directly on the sill, causing severe structural rot and getting behind the building structure. Installing metal kick-out flashing or custom diversion plates can redirect the runoff safely away from vulnerable spots like window sills and porch sides.
What the numbers show
Counted from the threads quoted below. How we count
- People have been saying this in most months since September 2026.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Adding a gutter to the upper section or roof edge to redirect water flowDid this help you?
- 2Installing flashing at the roof edgeDid this help you?
- 3Applying a wood hardener or penetrating epoxy to the sillDid this help you?
- 4Replacing the rotted sill and trim after proper re-flashingDid this help you?
- 5Installing kick-out flashing under the shingles or claddingDid this help you?
- 6Adding a small splash guard on the gutterDid this help you?
- 7Applying silicone on an angle to divert waterDid this help you?
- 8install a float switchDid this help you?
- 9periodically flushing the line to keep it clearDid this help you?
- 10turn off the unitDid this help you?
- 11nail a clear plastic bowl to the ceiling or superglue a condom over that holeDid this help you?
- 12removing the elbow and pushing the extension upDid this help you?
- 13checking for a blockage and adjusting the slopeDid this help you?
- 14replacing the corrugated extension with smooth PVCDid this help you?
- 15cleaning gutters more frequentlyDid this help you?
- 16installing a sump pumpDid this help you?
- 17having the front yard professionally graded toward the streetDid this help you?
- 18building a landscaping berm to direct water away from the houseDid this help you?
- 19Replacing the roof with a flat roofing solution using base and cap sheetsDid this help you?
- 20Filing a claim directly against the roofing contractor's liability insurance.Did this help you?
- 21Hiring a water remediation and mitigation company immediately to run commercial dehumidifiers.Did this help you?
- 22Removing and replacing all wet attic insulation and drywall to prevent mold growth.Did this help you?
- 23Holding back the final payment to the contractor until all interior repairs are completed.Did this help you?
- 24hiring a landscaper or earthworks company to grade and correct drainageDid this help you?
- 25installing a sump pump at the lowest corner of the crawlspace to discharge water to the streetDid this help you?
- 26installing a French drain to redirect runoff away from structuresDid this help you?
- 27installing surface drains into a pit with multiple outflow pipesDid this help you?
- 28Adding an extension or corrugated pipe to the gutter downspout to move water away from the foundation.Did this help you?
- 29Digging out the dirt at the downspout and filling it with rocks to create a drainage pit.Did this help you?
- 30Installing a rain barrel at the downspout to catch the water.Did this help you?
- 31Raising the patio stones so water flows away instead of pooling in the middle.Did this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“our crawlspace has been flooding for Lord knows how long”source ↗
“The crawlspace was the biggest issue as our support piers and the foundation walls are sinking and shifting from years of repeated water damage.”source ↗
“don't want the huge snowbanks of meltwater running into the house like it's done for 50 years”source ↗
“Whenever we get heavy rain I end up with water under the house and in my shed.”source ↗
“I had a similar issue of water under the house during heavy storms.”source ↗
“Had the same problem with our mostly paved very large area, so caught a lot of water! Slopes down to the back shed that’s been lined for kids playroom/sleepout. Wasn’t ideal when it was all underwater..”source ↗
“Of course it completely poured at the most pivotal moment where they were ripping off decking and everything was exposed. They put tarps down, but they did not work. Water was coming from all over the place, as you can see in the video.”source ↗
“But I can tell you that almost every room in the house showed signs of water intrusion. Now I have to worry about mold.”source ↗
“I'm trying to figure out a way to install some kind of flashing to fix the problem of water dripping behind the gutter.”source ↗
“The one and only time this has happened to me, I was over there the next day with a couple guys helping the homeowner remove all his insulation and then paid a company to blow it back in. Felt terrible and made $0 profit on that job”source ↗
“I had a home get wet at the beginning of the year during the re-roof process. The homeowner was any attorney and he never asked for a discount just for the ceiling to be repaired”source ↗
“We just had the same thing happen. All your insulation and ceiling drywall needs to be removed and replaced. Have the roofer file an insurance claim. Thr total cost of our project was over 70k.”source ↗
“I should mention I removed the leaf guard because I thought that was the main issue, but it didn't fix it.”source ↗
“I had a similar problem and installed something like a metal kick-out flashing to divert water.”source ↗
“Water overflows from this side and lands on the cill. It’s actually deteriorating the cill so bad that it’s getting behind the structure and starting damage.”source ↗
“Im thinking about just getting a steel plate and nailing to the side of the porch roof then caulking it, but would like to hear better ideas.”source ↗
“Water just backs up and out and it just floods this area.”source ↗
“The top of my gutters are clean but I can’t say the same for the downspouts because I can’t see into them.”source ↗
“Water coming down from the soffite”source ↗
“Moved into this place recently and want to redo the back patio. Had the first real rain since settling in and the whole area ended up flooded.”source ↗
“My only thought at the moment is raising the stones in the middle so the water doesn’t pool.”source ↗
“Should’ve included more info but unfortunately it’s a small patio that leads to a parking lot. Townhome rental. The pavement opposite the fence drains poorly as well, and much of it pools back under the fence.”source ↗
“This is a closet I don’t use often and it’s taken on a lot of water before I realized what was happening and could shut off the AC.”source ↗
“I’m tired of having my closet randomly flooded once a year. What options do I have here?”source ↗
Where this came up
People with this problem also raised
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- 13Basement window level with the ground water leak prevention
- 5Can you use silicone to seal gaps around a shower drain?
- 5How to stop water from splashing out of sliding glass shower doors
- 16How to fix a dipping flat roof that collects standing water
- 3Is a chimney cap necessary to stop leaks and animals?