13 Little Talked About Reasons on What Causes Basement Flooding10 min read

13 Little Talked About Reasons on What Causes Basement Flooding10 min read

Did you know what is the #1 disaster in America?  Flooding!   In fact, the majority of those houses are not on flood plains.  If you have a flooding or fear one, I know a bunch of questions runs in your mind including the causes of basement flooding.  I’ll try to provide as much as information to equip you.

There a lot of reasons for basement flooding.  Major reasons are seepage of water through walls and floors due to foundation issues.  Rainwater is an important surface water source.  Other primary reasons are stormwater breakout or sewer backup related issues.

Let me break it down and provide other causes so you can protect your investment well.

Top 13 reasons why a basement flooding happens

Flooding Under Wet Conditions

The vast majority of reported flooding happens under wet weather conditions. That is when there are rain, snow, and storm.

Now, you might have a failed system, such as a cracked foundation wall or a foundation drainage issue. That would just worsen the situation under wet conditions.

Even if all your systems are considered fine, the condition just stresses the system and can result in a catastrophic flooding in the basement.

1.      Overflooding and Surface Intrusion

When there is a hurricane followed by a heavy downpour, you are at risk.Flooded street due to heavy rain floods basement

And if your city stormwater system can’t gobble up all the water, you are out of luck.

Several things can happen at the same time.

The power outage can happen, that will leave your sump pump with no energy.

Plus, the rainwater is beyond normal stressing your system even if it works making the problems exponentially worse.

When there is heavy rain puddling around the house or change in weather making the snow melt rapidly can force water to intrude your basement

Surface Water Related Issues:

Surface Water is one of the major reasons for flooding.  There are several points of failure for you to have the basement flooded.

2.     Water Intrusion

Water table rises rapidly for several different reasons.

Cracks in the wall, vent holes around the basement, gaps around basement windows and many other paths lead to a flood in the basement.

3.     Failed Sump Pump

The fact that you have sump pump essentially means, the water drainage system is not efficient just using gravity pull.

Sump pumps are necessary to tackle the groundwater issue.Sump pump installed in basement with weeping tiles to avoid flooding

When the sump pump fails, it is almost guaranteed that your basement will floor.  Especially when you have other conditions that can raise the groundwater level.

4.     Deteriorated Weeping Tiles and Sealant

Sealant around the house foundation is not a permanent one. It needs maintenance.

If you have Tar painted around the foundation, know this.

Tar is not elastic, and it will break and crack.

Weeping tile can get deteriorated and any number of things used in the construction can go wrong over time.

5.     Grading Issues and Landscape Slope

When there is rain, there are a lot of things that can go wrong.

Grading is your make or break point.

If the ground around the house is sloping down and away from your house you are good.

However, there might be a portion of the house where the landscape wouldn’t be sloping properly.  I have even seen an inward slope.  That is, ground few feet away is usually higher and the slopes down to hit the foundation wall.

When you have a slope issue, water puddles around the basement foundation.

Even if you see no water in the basement, it’s just a disaster waiting to happen.

When a crack forms or your drainage system around the footer fails, it immediately results in a flooding in the basement.

6.     Overflowing Gutters – Debris, Leaves

This is an often-overlooked reason but causes a major headache to owners.Gutters overflowing dumping water near foundation for flooding

Cleaning gutters is a 30 min job but not doing the proper maintenance is going to cause havoc.

Gutters get filled with debris, leave branches and residue from shingles.

All of this clog the gutters.

When gutters are overfilled with dirt and debris, the rainwater from the roof starts overflowing.

That causes puddling.  Again, it might not be sloped there and maybe a flat ground.  Because it was not intentional to have water puddle there when constructed.

Water goes straight down to the basement.

7.     Clogged Downspouts and Missing Extensiondumping roof water by foundation - Downspout extension missing

This is a less than $10 fix and I don’t see owners doing anything about it.

When builders build they leave the downspouts to end just when the downspout touches the ground.

I checked a $1.5 Million new construction house.

Believe me… downspouts just stopped by the foundation.

I don’t know why, but they don’t finish this part and it irritates the hell out of me.

Go get a downspout extender and let the water exit a few feet away from the foundation.

Just to be doubly sure that it does not enter the groundwater around the foundation and flooding the basement.

8.     Sewer Backup

The city systems are not perfect.  They have to maintain their systems frequently and if your city fails to do that, the sewer system can create a problem.

Now, without going into the reasons, we just have to the risk and how it can affect your house.

When groundwater goes up, there is a breakage in their system or any other issue the city sewer is going to be building up.

If your sewer system throws more water in, it’s going to back up.municipality city water sewer breakage causing backflow of sewer water in basement when it rains

Let’s say your house set slightly below your neighbors you are in trouble.

If they push water in, since the city sewer is clogged, the lowest point of existence is where the water will come out.

Since your drain pipe is the lowest point, all your neighbor’s sewer dump ends up in your basement.

To prevent this, you need to put a sewer backflow preventer.  It is a simple value that will be installed in the sewer line outside your house before it enters the city system.

So, if you flush the value will let the wastewater flow out, but when the city system tries to push the sewer back, the valve will shut.

This is not an obvious one for owners, but a must have to save you from a big catastrophic event.

Flooding Under Dry Conditions

9.     Blocked and Broken Sanitary Lines

This is a classic issue with old homes.  The sewer line that connects the house to a public system fails.

I have had this issue once.  An older home that had clay pipe running the sewer.  A neighboring tree’s root intruded and broke the crushed the pipe.

When a sanitary lateral fail, it’s usually the house’s wastewater that is backing up and flooding when you are not aware of the issue.

Another major cause if dumping stuff that is not recommended for flushing.


Sanitary lines should carry human waste, grey water and toilet paper (a degradable one).  That’s it.

For everything else, you got trash cans.

10.   Supply lines and Hot-Water Tank Failure

Even if you have copper pipes in your house, sooner or later it is going to develop pin holes.

When that happens, you may not know but it will start leaking and before you know you have a flood one day.

Same applies to your water tank.  While the water tank might look solid, the lining inside might be rusting.

When the lining breaks it floods the basement.

11.   Failed Foundation Drainage System

A lot of houses has a French drain setup or a variety of different foundation drain solution installed.

Not everything is perfect forever.

Weeping tiles will degrade, and sediment plugs the drainage over time causing an issue one day.  Sump pump might also get blocked.

12.   Crack in Walls and Foundation

This a major issue.  You might have had the best foundation and a foundation drainage system around the perimeter of the footing.

But over time as the house settles, the foundation can form a crack and water can seep through those.Floor crack water seeping in basement flooding

For a while, your weeping tile might catch it.

But if the amount of water that intrudes become excessive under certain conditions, the drainage system can’t keep up, resulting in a disastrous.

13.   Irrigation

If you did the irrigation yourself or using a not-so-knowledgeable contractor, it’s possible the irrigation is set up close to the foundation.

You can avoid this by calibrating and controlling the water it throws from the outlet closest to your house.Basement Flooding due to Garden Sprinkler Dumping Water

Especially it should not dispense water when there is rain.

Basement Floods During Heavy Rain

I have given many reasons for flooding, above. However, if you end up with frequent basement flooding during or after rain, I want to clarify something.

If your basement floods every time it rains you’ve to act quickly, you might just have a big problem that needs your attention.

But, let’s say you see water coming up from basement drain after rain, then you have a specific issue.

There is another similar issue – you might be wondering why your basement drain backing up when it rains.  Let’s cover all the Cases.

Basement Floods Every Time It Rains

You have a big issue at hand and must act quickly.

The main reason is the groundwater table is rising quickly and there is a vulnerable spot in your structure.

It’s mostly your walls. There is probably a crack in it.

If you have an older house, then probably you never had a waterproofing done outside and you need to install one.

Let’s say you have a relatively newer house.  In this case, it’s either a poor job by the contractor or a deteriorating waterproofing. Tar or any other non-elastic material will break letting water in.

If the amount of water is not too much but consistently flood, you can get away with a perimeter drainage system (French drain) and a sump pump.

Remember this:

You must address this issue immediately because there is a potential hydrostatic pressure issue. This will cave in, crack and bow your foundation walls.

Act immediately.

But there a few things you must look do regardless.

  • Drain water away from the foundation. – use downspout extenders
  • Clean gutters and downspouts
  • Grade and slope the landscape around the house

Basement Drain Backing Up When It Rains (or) Water Coming Up Through Drain

This is most likely a failing city sewer issue. Just check around with your neighbors to see if anyone is finding this issue.

When there is a heavy rain the water backs up in the city sewer system and stormwater drainage system. If there is stress in their system, it pushes water at weaker spots – which is your drain line.

Talk to your city to look into the issue and address the issue before it becomes big.floods basement when it rains city sewer clog removal by public works

But, you don’t have to do anything for the basement flooding through flood drain issue. As the stress relieves in the city sewer system, the water will drain.

Once the city sewer comes back to normal flow, the standing water in the basement floor drain will automatically drain back without issues.

Like I mentioned earlier, backflow stopping valve will come in handy to stop this issue.

Is basement flooding covered by homeowner’s insurance?

I know this question warrants a separate post, however, this is a nagging question, so I thought of giving a short answer here.

The short answer is NO.

But as you know insurance is a different animal altogether.

When it comes to insurance companies one size doesn’t fit all.

But in general, standard homeowner’s policy excludes flooding. You must have taken a flood insurance separately.

If they find the issue was due to a maintenance issue or a neglect of the property, that is also a case for not covering.

I know they find ways to not pay you, right?

But I am going to give you situations where they cover, and you should submit a claim.

Cases where the homeowner’s insurance cover:

  • Broken Appliances
  • Hot-Water Heater
  • Sudden Pipe Burst
  • Anything that’s sudden and accidental

Generally, any case where it’s an act of nature, or due to neglect in maintenance, is not covered

Wrapping up:

Basement flooding is avoidable if you take precaution.

Most of the maintenance will take less effort and costs you very little. However, the maintenance saves you a big headache and a lot in remediation costs.

Majority of the flooding happens due to failed mechanical, so check and keep them running properly.

Other main reason would be the groundwater, so grade them and drain them away

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