Little

I currently have I guess what they call a floating concrete basement floor as the slab has about a 1 1/2" gap around the entire interior perimeter. I'm a first time home owner and don't know too much about this stuff. What is the reasoning for this? Also why don't they just seal up basements completely? Was this just due to old techniques? The house was built in 1965.

Basically i'm trying to get the basement dry as the bottom two feet or so up from the floor has that black mold & white mold. What are my options? I will do all work myself as well. Am i looking at doing a full exterior footer drain with full wall membrane? I plan on finishing the rest of the basement which is why i'm looking to start addressing these issues.

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genecarp

I am not familiar with a technique that creates a 1-1/2" gap around the basement perimeter unless there is a drain pipe hiding in there, i can however speculate that you have serious water conditions around your site, The previous homeowner may have created the gap as a way of recieving the water as it beat the foundation, if you dig down you may find a drain line below that gap. Quick lesson in basements----Some conditions, you keep the water out of the basement entirely using standard waterproofing techniques. Other conditions mandate that you have to deal with the water on a regular basis using french drains /pumps etc....Sound like you have condition 2/, one way is to cut back the perimeter further, place perforated pipe around the perimeter , set in gravel, this pipe must all pitch toward a sump, with a pump that will pump the water out of the basement. Also if you just moved in, it will take a full year to discover just how much water you are dealing with, as water tables fluctuate as the seasons change. I am just scratching the surface as far as conditions and options, GMOD.

PS regarding the reason for not closing up the slab, pressure, water pressure can and will crack a slab, that gap may be preventing that from happening, HYDROSTATIC PRESSURE, i think

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Mike Finley

Yeah, like what was said... basements aren't built to be boats.

You either keep the water drained away from the outside or you drain it from the inside, but they won't be built water proof. There will almost always be water trying to get into any basement, you deal with it by moving it away.

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cleveman

Mister you are screwed. I doubt if you have any vapor barrier underneath.

You've got to have the drainage underneath, which as someone mentioned, you can put in after the fact. If this is the case, I see a concrete saw in your future. Shouldn't be too big of a deal with a couple of blades. Make sure you have one with a water connection to keep dust down, and ventilate the area so you don't die doing this.

Now, what to do about the vapor barrier? It should be under the concrete. I would first find out if there is a vapor barrier. Knock out a piece of the slab somewhere to check. If there is not a vapor barrier, what is the square footage of the slab? If you say 900 square feet, I would consider just removing the slab and starting over with proper drainage, insulation, vapor barrier, and you might as well install radiant heat while you are there. Then new concrete and you have really achieved something. You should install a radon ejaculation system at the same time.

You'll have to make the call based on how much you want to spend.

oldfrt

When I built my house,I noticed the water level was 2" below the stone(before slab was poured) after heavy rains.
We poured a conventional slab, with plastic over stone,and of course full exterior curtain drains.
Never had a problem as water will take the path of least resistance,which for me fortunately,was through the pourous soil to the curtain drains.

There are systems to eleviate flooding,but I would think that keeping as much moisture away from a finished area is going to be your best remedy.
Got to check soil conditions in your area and get a hold of someone that has a lot of experience at this.

You got the right idea,but you will have to get a good interior seal to proceed.

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cexcavation

I really hope you meant to say "evacuation". If not, I would be very curious to see how a radon "ejaculation" system works. I have a few guesses, but none of them are appropriate for this board.

cleveman

This is a very simple procedure. You just put a switch on the in-line fan. You switch the fan on, and the gas is ejaculated. Leave the switch off, and it is evacuated.

Blas

Little

This is just my two cents. You have a floating slab. It is designed to move up and down with the water table/Elastic soil you have underneath. If it was me I would:
1. Demo the slab entirely ( it is impacted with mold ie no vapor barrier.)

2. Gut the inside out 1 foot deep, Install interior 1 foot of free draining rock

3. Install Perimeter drain tile and cross the Drain tile under the slab. install two sump baskets and pumps. Make sure the (Drain tile is lower than the sub grade) so 1 foot deep under slab and 1.5 feet deep where the Drain tile runs.

4. Install radon vent pipes/ just 2" perforated pipes that run in the gravel and vent outside with an exhaust fan. (This is good insurance and looks good for resale)

5. Install 15mil Stego wrap Vapor Barrier. Tape the seams with the recommended tape (not duck tape). Tape the seams and tape the perimeter wall system make sure you repair any rips (good luck ripping) You can lower the vapor barrier into the rock layer if you want to protect it just add the rock over the top 2-3 inches.

6. Reinstall floor slab with #4 re bar with 1/2 inch gap this time. This will help the slab to stay a floating slab that does not crack up and go to hell.

7. Continue with foundation waterproofing and tie draintile into sumps. This outside waterproofing is important do not cheap out on this. You can put in the Mirafi drainage sheets after the membrane is applied this will keep water off of the wall and give it a direct path to the draintile rock. It also protects the membrane from damage as you backfill. Some people install Rigid foam insulation at the outside of this drainage sheeting. Not sure of your insulation requirements.

Thats what I would do if it were me just my two cents everyone has good advice. I just know that you and I are a lot alike from your posts little and you probably have access to materials and equipment, so sounds expensive but in actuality what would cost a typical home owner 15 grand will cost you maybe 5.

P.S I tend to overkill things that are my own.

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