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How to Prevent & Fix Flooding in Your Seattle Basement (It’s Not the End of the World, Promise!)

In case you haven’t noticed, every so often in Seattle, it rains! And every few years (it feels like it’s every 5 or so years), we have a massive “water event” where we get a ton or rain and/or snow. Usually this is how it goes: It snows a lot (for Seattle, that is), then it rains a lot, which melts the snow. Then, like clockwork, a ton of Seattle basements flood. And Seattle is a city of homes with basements! 

We have seen it all when it comes to flooding basements here in Seattle. At the end of December/beginning of January, we just had many of our clients reach out to us needing help with their flooding basements. And we are happy to help!

In this blog, we’re going to give you our tips and tricks for how to #1: avoid basement flooding, and #2: fix your basement when water inevitably creeps in (remember, it’s Seattle!). 

If you are a homeowner in the Seattle area, it’s really important to know this: Even a very good and dry basement can fail. All basements can get wet. Period! 

Keeping this in mind, it’s just important to know how to take precautions to avoid preventable situations, and if you do get flooding, how to fix the problem.

Here are a few common issues and how to avoid flooding in your basement: 


When water hits your roof and ends up in your gutters, it goes into your downspout. That water has to go somewhere, and ideally your downspout is pushing water away from your home as it hits the ground. 

Unfortunately, downspouts are a common failure point, and especially if you have an older home, you have to look out for concrete downspouts or concrete pipes that have failed one way or another (they might be clogged, cracked, collapsed, etc.). If any of this has happened, water is going to ultimately be pushed toward your house and start coming inside. Concrete is porous, and once water builds up against basement walls made of concrete, the concrete will start to soak up water like a sponge and come into your home. 

One way to avoid this is to get a high-quality splash block. Get the water to run away from your house. When it’s just sprinkling outside you don’t have to worry about things too much, but when it really pours or when the snow starts to melt, you’re going to be glad you took precautions ahead of time. 

Basement entries

This is something many home buyers and homeowners might not think twice about, but your basement entry needs to have a drain that actually drains properly. This is especially important to keep in mind when it snows or is super cold out—the door drain can ice over, and any water that builds up is going to miss the drain and come right into your basement. If you know it’s freezing outside, check your door drain to make sure it’s clear of ice. And for that matter, make sure it’s clear of other debris like leaves, too. 

Basement floors

Beautifully polished concrete floors!

Sometimes water just comes up right through basement floors. After a big “water event,” the water table may rise higher than the floor of your basement. You may notice water coming in through the cracks of your concrete. (Remember, concrete is porous and it’s going to absorb water like a sponge.) Matt just remodeled his new home and he just polished the concrete floors and they can conveniently get wet to some extent. On that note, never use wood floors in a basement. Always use tile or vinyl flooring. 

You should also install a sump pump. A sump pump is truly a magical invention for Seattle basements. A sump pump is used to remove water from an area, most commonly—you guessed it—basements. This is an easy, cheap thing to install before you finish a basement if you are remodeling one. If you’re buying a home that has been flipped, they almost *never* install a sump pump. So if you’re touring homes, this is something to look for. Do you see evidence of a sump pump anywhere? 

This window’s seal is a mess! Water splashes against the house and window anytime it rains and gets into the basement through here.


Another weak point in a basement are windows that have not been sealed properly. Water can easily pool up around windows and splash up against them too. 

Rain barrels

If your rain barrels are getting full and you know a big water event is coming, empty your rain barrels (away from your home, that is). These will just spill over against the wall of your house, and that water is going to leak right into your basement. 

Snow sitting against your house 

When it snows, don’t just let the snow just sit against your house. Get out there and shovel it away from your home so when it melts, the water isn’t right up along your home. 


So… how do you avoid buying a house in Seattle with a basement that’s going to give you flooding issues in the future? 

To reiterate our intro: Even a very good basement can fail! However, there are precautions you can take. And if you’ve been following us for awhile now, you probably already know the simple answer: Work with an experienced real estate agent who knows the ins and outs of what to look for in a Seattle home (and basement!). 😉 If a basement has some red flags, they can at least let you know what they are so you can fix them if you decide to buy the home in question. 

Another smart thing to do is to bring a moisture meter when you’re checking out a home. Matt always carries one in his car. You can use it to detect moisture behind walls to get *some* clue as to what’s going on with the home. 

When the moisture meter reads anything up to 9% or 10%, that’s pretty normal. Most types of building material will just naturally have that. Up to 14% is even ok. 15% to 16% is starting to get high… and 20%+ has us thinking, ok, something bad is definitely going on here! 

22.5%… not good!

In older homes, it might be easier to spot water damage, but it’s not always obvious. And spotting water damage or red flags for future water issues might be near impossible in homes that have been flipped or newly remodeled. You may not see any evidence of water intrusion, because there hasn’t been time for water intrusion to reveal itself yet. If this is the case, look for any area of the basement where you might be able to see exposed concrete. If you see anything white and powdery on the concrete, this is potentially lye that water/moisture is pushing out of the concrete. This means there is significant moisture present in the basement. 


What do we do if our basement floods? 

If your basement ends up flooding, there are few things to do. We are always happy to help and lend our advice to all of our clients! We also always love recommending Wu Construction (based on Lake City Way in Seattle) whenever our clients are having basement flooding issues; Wu Construction does an incredible job. They don’t oversell you on things you don’t need, which is always the fear with flooding issues. Some companies will come out to your house and they’ll want you to spend $30k – $40k to do everything under the sun when it just might not be necessary, and we love that Wu Construction gets to the root of the problem and just fixes that. (Promise this isn’t sponsored by Wu Construction, hah! We just love them!) 

Here’s a real life scenario where we helped our clients sort out a flooding issue.

Here is the deck that’s right above the basement door. This is where the water was getting into the basement.

In this case, their basement was located right under their deck, and water was pouring through the deck and soaking the beam right above the basement windows. This was happening because the flashing (an L-shaped piece of trim and a super easy fix) was not installed underneath the door, so the water came over the edge and curled back in, soaking the beam below the deck. 


We took out the whole wall and had to remove the sheetrock and insulation.

Here’s the beam that was getting soaked.

We also had to pull up the carpet and padding, dry it up, and put it back down. The blue thing in the photo is an industrial dehumidifier we had running to dry out the space along with air movers to ensure we didn’t get any mold growth.

You’ll also see that the home’s water meter is filled with water. There was definitely a “water event”!

All of this work cost $5k, which is not nearly as expensive as most people expect when water damage or flooding like this happens. 

Have a question about basement flooding or anything related to Seattle or Eastside real estate?

We’re happy to help! Click here to get in touch! 



Want to know more?


Matt Miner

Real estate guru and Seattle know-it-all


In everything that I do as your REALTOR®, I have one guiding principle in mind: To make certain that your home-buying or selling experience is a happy, successful, wonderful life experience! We build trust and security with our clients using knowledge and transparency.