Flooding basement

I built a new house back in 2020, great house that fits most of our needs very well. Unfortunately, the water table is very high so when it rains more than an inch or so I battle water incursion. The basement isn't finished so no worries about ruining stuff or whatever it's just annoying.

Brainstorming with my wife and some friends we hit upon adding another poured concrete floor on top of the existing one to get us above the 2" above the floor that the heaviest flood gave us. My concrete guy said he has done a floor on top of a floor with a membrane of some sort between existing and new. 
 

Has anyone done this? Heard of it? Thinks it's outrageous? It won't ever be a finished basement but I don't want to have to divert water whenever there is a major rain event.

As an aside before I'm told to put in a sump pump; I have two sump pumps in the basement already and they are unable to stay ahead of the water. The pits never overflow so they are doing their job. It seeps in a little here and there.

Does the basement have 7ft of headroom currently?  Building up the floor by 2ft could only leave you 5ft of headroom?  

Actually 8' except where the beams are, I have no problem painting them pink and wrapping them in pool noodles. Just don't want the water haha

Two pumps running continuously. Oof.
 

This is an opinion... Water has to be controlled on the outside of a basement. It probably needs to be trenched for a French drain, plus slab and exterior waterproofing, and grading to slope away from the house. Unfortunately, all that should have been done when the house was under construction.  
 

Maybe a Chinese mini excavator and some drain tile?

From the outside, would these kind of guys and some Hancor pipe be the solution?  

tester (Forum Supporter) said:

Two pumps running continuously. Oof.
 

This is an opinion... Water has to be controlled on the outside of a basement. It probably needs to be trenched for a French drain, plus slab and exterior waterproofing, and grading to slope away from the house. Unfortunately, all that should have been done when the house was under construction.  
 

 

Exactly this.  Fix it once, fix it right.  TBH it should be on the builder on that new of a house.  If it was a problem since day 1 and you had the place built...woof...  I would be cheesed.  

The water table is to high to be controlled on the outside, if I shut the pumps off during dry times which is fine it levels off about 8" below the floor level. The builder has zero responsibility for the lot so all of that is a moot point; and yeah I've been cheesed off for five years...

How about this floor? Anyone heard of it?

And before everyone comes back and says there is more to do out side; I added tiles channeling all the water either way around the house as well as footers pulling water to a 48"x13' tile with four more pumps in it to move the water away. I have monitored and played with this ever since they were building since it was dry when they dug the foundation in 2019 but started getting wet during the spring of 2020 and had issues from the beginning(including having two hydrologists look it over in separate years). Arbitration accomplished nothing. The final level of ground water during a major rain event appears to be 2" above the floor of the basement so at this point I'm bowing to the water and thinking I will be perfectly happy with a lower ceiling. 

edit: this is not in a subdivision; it is in the country on my piece of land that I've owned for a long time. I lived in a trailer (obviously without a basement) on this property while I saved to build a one time house and cheesed off is over at this point. Ready to worry about something else. The one to the north all slopes down toward the river that is in the tree line to the south; when I originally went over the county maps they showed the water table low where I chose to build and that the water moved along to the east of my house on my property and the neighboring field. Obviously not correct.

tester (Forum Supporter) said:

Two pumps running continuously. Oof.
 

This is an opinion... Water has to be controlled on the outside of a basement. It probably needs to be trenched for a French drain, plus slab and exterior waterproofing, and grading to slope away from the house. Unfortunately, all that should have been done when the house was under construction.  
 

 

This was done, as above; it was dry when we originally did the work but as it got wetter in the spring all of the work didn't keep up. Ive revamped and reworked the tile and all drains but nothing really works for the quantity of water.

in the outside sump during a major rain event  I use two FOUNTAIN pumps to keep it clear just running the lines around to the front side of the house. It's an insane amount of water crossing the property on its way to the river which is one field away and below my house.

Years back, my inlaws did this style interior, perimeter channel to their previous long time home.  Their property, as the crow flies, was less than 1 mile from Lake Erie.  Keep in mind that all water flows toward the lake.  Their property sat about 6ft lower that the houses across the road from them.  That means that a lot of water flowed their way and they always had water issues.  

If I understand correctly, this perimiter piping not only served as water collection but it also provided many square feet of water retention,( if needed) to hold more water than the crock could hold in major rain events.  

It sounds like your guy want to provide secondary water retention under a second floor.  This moves that secondary retention to perimeter piping instead.  

I've actually moved the exterior water as best I can tiles and French drains attempting to move it around the house; including the tiles running into a 4x13' sump on the outside that then pumps that water away

All I want to do is add concrete to the floor; 4 or 6" so that it doesn't come in every major rain event. My normal concrete guy said he's added to an existing floor successfully although it's never been for this reason. The other guy I talked to said he had done a basement in the heavy flood area here the same way successfully. Knowing we have a lot of construction minded people here I was hoping someone had seen or done this.

chandler said:

I built a new house back in 2020, great house that fits most of our needs very well. Unfortunately, the water table is very high so when it rains more than an inch or so I battle water incursion. The basement isn't finished so no worries about ruining stuff or whatever it's just annoying.

 

Brainstorming with my wife and some friends we hit upon adding another poured concrete floor on top of the existing one to get us above the 2" above the floor that the heaviest flood gave us. My concrete guy said he has done a floor on top of a floor with a membrane of some sort between existing and new. 
 

Has anyone done this? Heard of it? Thinks it's outrageous? It won't ever be a finished basement but I don't want to have to divert water whenever there is a major rain event.

I've done this multiple times, using a membrane as a bond breaker is very common. 

I understand that you've done a lot outside but basically 99.9 percent of the time getting the water figured out outside is leaps and bounds better. I see you've mentioned tiles and drains but not what waterproof you have painted on the foundation itself? I've literally done jobs that have streams running against them and are literally underwater, they stayed dry.

Concrete is a sponge, water near it is being drawn thru it too so that's a concern 

That's what I was wondering; I've seen you post concrete info before. I do not know what the foundation was coated with (though I know it was) and haven't really looked back in my paperwork since the water does not come through the walls at all, it seeps up from beneath. As for the underground stream one hydrologist said that is exactly what it is though the other one called it a fast moving ground water. Whatever the difference is....

So; knowing the "flood stage" is about 2" above the current floor level would you feel comfortable adding 4 or 6"? No one says what happens down the road and I can find zero info online about doing this. I plan to die in this house so I'm looking for as permanent a solution as is possible. Thanks!

chandler said:

That's what I was wondering; I've seen you post concrete info before. I do not know what the foundation was coated with (though I know it was) and haven't really looked back in my paperwork since the water does not come through the walls at all, it seeps up from beneath. As for the underground stream one hydrologist said that is exactly what it is though the other one called it a fast moving ground water. Whatever the difference is....

So; knowing the "flood stage" is about 2" above the current floor level would you feel comfortable adding 4 or 6"? No one says what happens down the road and I can find zero info online about doing this. I plan to die in this house so I'm looking for as permanent a solution as is possible. Thanks!

I wouldn't be sure that just adding a concrete cap would fix your problem. It takes a huge amount of hydrostatic pressure for water to come up.

My bet is that water is coming thru the footing to wall seam and puddling under the concrete floor. I'll draw a thing here in a sec for a visual

Here's what I think is happening. Usually " I have a stream around my foundation" means a stupendous amount of water. Since you've said its just a little seeping sometimes I think they half-assed the waterproofing at the seam, because they almost always do. You want to ram a ridiculous amount of tar/asphalt/waterproofing in that area.

It's also usually below the slab which makes sense why it's underneath the slab

If you do do a cap you'll want to be insane about the waterproofing, like ....consider a pool liner or like..,....4 levels of waterproofing before you pour the slab.

I'd go much higher than you think and concrete is expensive, 6" deep will be many many yards of concrete

The best way to fix it, and I have done a lot of this, is to lower the water table around the outside of the house. I expect you have a perimeter drain already in that sort of ground water, so you may be able to work with it, or you may need to dig another, deeper one a bit farther from the house. Perimeter drains usually lead to a rock pit which fills up and then is pointless. If so block it off or add a gate valve so it can be shut at times of high water table. The perimeter drain should be bottom of footing level at a minimum but if you have a big footprint the water table will rise in the middle so lower is better to keep ahead of the mounding effect. The cheap way to start is try using what you have, but lead the pipe at opposing corners off into sumps several feet deeper than the footing and put big ass pumps in them. They should be big enough to pull all the water away from house within a few minutes. The deeper you get these sumps the less often the pumps will have to run. Think half horse pumps or bigger. If you still get water then you need to dig a deeper perimeter drain a few feet out from the house. Also be sure your downspouts are directed well away from the house. That is a ton of water that will add to the problem. If the damp proofing was poorly done you may need to dig around the house, pressure wash the foundation and reseal. Lots of work but a lifetime solution.

First, I'm sorry you are having to ask this.

What elevation is your basement floor relative to the river and do you own the land between the river and the house? How recently has the river flooded out onto the adjacent fields?

I am sure some civil and geotechnical engineers are among us and they are certainly more suited to speak to this topic but.. I have worked on the design and construction of multiple very large buildings below the water table, including a parking deck 30' below water table in a town literally named "sandy springs" so I have some experience in this stuff.

In all cases we built a water tight perimeter wall and drained the base of the walls into a gravel and pipe FILLED drain field under the floor slab - then pumped it into a cistern (or out to the storm sewer) or detention vault.

We also designed the floor slabs and walls with pressure relief mechanisms, and slab sawcuts to allow the building to remain standing in case the upward pressure got too extreme.

Your description sounds like all of the suck because it is too late to build a "bathtub" that is fully waterproof under the slab and around the walls.

I believe if you pour another slab inside the basement you will find yourself chasing the same ghosts in the future. 

So the alternative is more collection, drainage and more pumps. It sounds like you need a bigger underslab drainage system. This means removing the existing basement slab and digging trenches and adding filter fabric, stone and perforated pipes (or just filling the bottom ~12-24" of the basement with clean stone), all draining to a larger sump vault, then "inserting a straw into the cup and sucking that straw forever" - by paying for the electricity to lift that water out. Just like you have today, but more.

I asked about the elevations because it would be much better to drain by gravity than by pump(s) which would very likely need backup power when you need them most. 

I helped build a house that was built on the wrong side of the road and there was a reason why every other house was built on the up hill side of the road opposite of the river. Almost immediately after digging the basement, the excavation started filling up. Instead of filling in the hole with crushed concrete and raising the house 4 feet, they dug a rock filled diversion channel and pipe 20 or so feet away and along the upstream side of the house and several feet lower than the footings and ran it hundreds of feet as a French drain which daylight exited near the river. I can't remember what the pipe's diameter was but it was a lot larger than 4" and it always flowed.

In regards to raising your basement floor, the Residential Code says that the minimum ceiling height for an occupied space is 7'-0". A typical finished floor to finished ceiling height for an 8' concrete basement wall is 7'-8-7/8" with a 5/8" drywall ceiling. Normally, you would add sand to fill the void so that you don't have to place 8" of concrete but for something that might always be wet, I don't know.

BuildingCodeTrainer.com: Minimum Residential Ceiling Heights Per Code

As a last resort, you could always fill in the basement with several feet of sand and then concrete floor and turn it into a crawlspace.

In reply to OHSCrifle :

Yes, the house is higher than the river by quite a bit. What happens now is the water on one side of the house is diverted to a natural swale that meets a culvert under the road (sorry owner of field across the road) and floods the field across the road on its way to the river. The other side collects in the sump I posted above which is 13' deep and is pumped through into a line that splits between an open ditch (that then heads downhill to a different culvert) and the field tile in the field to our west. This last rain event I had FOUR 3/4 sump pumps in that pit and added two fountain pumps to stay ahead of the water coming in. I believe those fountain pumps are 111 gallons a minute and they ran nonstop to stay ahead. I'll also add that our gutters run to the field tile as well; we have an agreement with that farmer and it worked out well.
 

The field behind us and the one to our east are being tiled this summer once the wheat is off so it is possible that we can tie some of our drainage that way as well.... and it may lessen what sweeps through underground.
 

General consensus here is that the concrete floor may work but I should try more outside so I will table this and revisit what I've done and see what else I can do. Usually we see one or two of these events a year so hopefully I can make some changes before the next one. Thanks all!

If draining and collecting the rainwater is not enough-- and it sounds like the whole field sheet flows toward you and saturates the soil.. can you construct an earth berm on the uphill side of the house?

In reply to chandler :

As for outside and thoughts of ties into field drainage, since you are in a very agricultural setting, are there any agricultural resources like County Ag Extension or similar that might provide design help to a tax payer like yourself?

OHSCrifle said:

If draining and collecting the rainwater is not enough-- and it sounds like the whole field sheet flows toward you and saturates the soil.. can you construct an earth berm on the uphill side of the house?

There is no water on the top side in the path of the house, the only visible water is in the far end of my lawn near the natural swale. It takes about a day for that to disappear  naturally