Basement Slab Moisture

 
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Old 03-21-2017, 06:59 PM   #21
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Re: Basement Slab Moisture


At 250 CFM rating, most of which is air drawn from the the much closer basement floor, then the ground at least 7-9 feet of damp packed earth away.... With a properly installed drain tile ABOVE the bottom of the spread footings, most of the year in moderate climes the footer bottom is "wet", at the local water table level: saturated soil isn't very permeable... The radon fan is sucking on a water sealed chamber.... the path of least resistance for inflow is the cracks in the SOG.

Pealing the floor and caulking all the cracks and applying an air tight sealer would reduce internal air losses.

Negative air pressure leaking to basement causes unfiltered "dusty" air to enter the house and "drop" out as it slows, depositing the added dust....
This air is of course cold in the winter and hot and damp in the summer.

Worst case, radon fans WILL cause wet spots on the "wrong" side of existing Vapour barriers.

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Old 03-21-2017, 07:29 PM   #22
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Re: Basement Slab Moisture


I could see that as a possibility. Makes more sense now what you were saying.

My home is fairly tight, box sills sprayed with CC foam, good air sealing of penetrations, etc.

I actually did caulk all the perimeter walls with acoustical sealant when finishing the basement and the foundation walls have either 2" Dow or spray foam on them.

I was thinking of around 150cfm. My basement slab sq ft is approx 1600.

The whole reason I was thinking of the fan was simply for air movement under the slab.

Would there be a way to use the footer tile as "ducting" and simply create air movement under the slab without exhausting it out and putting the house in a negative state?
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Old 03-21-2017, 08:25 PM   #23
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Re: Basement Slab Moisture


I'm assuming your soil moisture/water is similar to here, mid 30s" annual rainfall, frost every winter, water table drops over summer fall to peak USUALLY after frost melts.spring wet season.

But in all put the driest years, the water remains at the bottom of your lowest tile, but ABOVE the bottom of any basement footing....

Thus your basement rock dry space under slab is around 4-8" Maximum, if your slab is sealed and caulked thoroughly, the Radon fan drawing on the under slab will raise the water table enough to constantly siphon water in all but the driest seasons. Your sump and radon fan will drying out several basements in your immediate area for "free" for them and $ on the sump pump (0.15$/Hr)....

FYI, I think most Radon installs are useless Scams IMO...

A little radiation is good for us, see Hormesis effect of "poisons"
And the fact current radiation limits were design by anti-US-nuke socialists working for the USA Post WWII Atomic weapons programs, assigned to safety engineering due to security issues, former card carrying commies mostly. No, you can't make this crap up, true story....

The current largest source of radiation in many US homes are the granite counter tops if installed...

If radon is so deadly, why aren't coal miners getting all sorts of lung cancers from radiation? wouldn't all those cave dwelling Neanderthals have cancerous bones in the museums? Hmmm?

Great salesmanship, an "elephant" repellent for the Mid West home owners, install the fan, and you' ll never see an elephant/radiation cancer......Guaranteed!

Theoretically you could pressurized the tile furthermost from the sump pit, and install just a straight DVW pipe to the roof line, it would draw a lessor negative amount, a furnace draft reduction damper could installed to prevent a large negative draft, but would still be exhausting conditioned air....

A Canadian style heat exchanger make up air fan could be used as an air source to pressurize the slab with less heating Costs... but real expensive (1000.00$+) Install costs.

Long run if your basement isn't finished yet, demoing the floor for a do over might by cheaper if you are staying for decade or more...

If the house's floor plan is simple and there are few/no attached structures, a house jacker could raise the wood up, lay a course or two of Block, and allow a properly detailed floor poured on top the old floor, cracked but left in place...

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Old 03-21-2017, 09:02 PM   #24
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Re: Basement Slab Moisture


First off I don't buy into Radon either. My only mention of it was using a fan used Radon mitigation because they are rated for continous duty and are a low cfm, quiet fan.

Your assumption of our area would be correct. My water level is usually 10-12" below the top of my basment slab. I can verify this with the normal water level in my outside sump. My inside sump barely runs.

Trying to wrap my head around how the fan would be drying my neighbors basement. Actually my next door neighbor is on a crawl and no one behind me. My basement slab doesn't have any cracks other than the control joints. It is still tight up against the poured walls.

Definitely not a grade issue. Top of foundation is 2' above the street with good fall all around.

I really am starting to wonder if there may have been an old field tile that didn't get noticed or cut off when they dug the basement in. Even in the middle of summer my outside sump will run.
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Old 03-22-2017, 07:47 AM   #25
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Re: Basement Slab Moisture


Did you or the installer put holes in the sump pit "barrel" below the bottom of the incoming tile(s)?

Many lazy installers punch hole so the pit won't "float" up prior to the Pouring of the slab..... WRONG ANSWER.

You NEVER want to de water the soil under the basement footings every year, as they will shrink and expand as the water % changes, possibly cracking your footings and walls....

Plus every inch lower costs money when you are pumping ALL the water with your light bill.. At a 1% grade on the water table inverted cone caused by your sump pit perforated an extra 12 " deep that is a cone say 8' deep with a radius of 9600" or 800', you are draining with a little help a cone ~1600' diameter top at grade About 5,360,000 cubic feet of soil if a flat land... at 7' deep tile pit lowest drain point, "Only" 3,990,000 cubit feet...
In heavy clays the cone would of course have a greater slope, less volume total....

If it just one spot in the floor, a extra tile line to the area to the perimeter tiles 'might' allow the "artesian' well to flow to the sump pit. if its just vapour condensing out on the ~55 degree or less slab temp.... A thermal camera might help localizing the areas with greater water vapor moverment

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Old 03-22-2017, 12:06 PM   #26
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Re: Basement Slab Moisture


Nope..no holes in either pit. Only the footer tile protrusion.
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Old 03-22-2017, 12:38 PM   #27
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Re: Basement Slab Moisture


I've really enjoyed learning from this thread. It's amazing the details that can come to play with moisture. I think Overanalize and Fourth generation could swap handles though.?
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Old 03-22-2017, 08:31 PM   #28
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Re: Basement Slab Moisture


It has been some good knowledge being shared and I appreciate Fouth Gen's and others input!
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Old 05-26-2017, 05:44 PM   #29
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Re: Basement Slab Moisture


Ok..so my hope of the fan helping/solving my issue fell flat. Not really surprised...it was a hail Mary.

Here is what the underside of the vinyl looks like and what is seeping through most joints in the floor.

My inside sump never runs. I spent some time with my outside sump and have the float dialed in to keep the water 7-8" below the basement slab or basically at the bottom of the footer tile but not the footer.

Looks like at a minimum I am peeling all the flooring. Are there sealers out there to prevent this?
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Old 08-05-2017, 07:38 PM   #30
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Re: Basement Slab Moisture


So I started pulling the floor. Most of it comes right up. I use a 6" drywall knife and scrape the glue off the flooring and the concrete. Again most of it comes right off and the concrete is wet.

I am planning on getting some adhesive remover and using our floor buffer with a black scotch pad to scrub the floor.

I am still not 100% what I want to do moving forward. I have found a couple waterproofing products that claim vapor and hydrostatic pressure resistance.

I have also been reading about Aquaflex PSA. Has anyone used it? It claims a 10 year warranty and doesn't require any moisture testing or ph testing. Seems like it could be the solution and still be able to keep the same flooring.

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Old 08-05-2017, 10:22 PM   #31
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Re: Basement Slab Moisture


Time to build a new house.

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Old 08-05-2017, 10:43 PM   #32
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Re: Basement Slab Moisture


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Time to build a new house.

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Yeah right! Maybe some time down the road but not right now.

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Old 08-06-2017, 08:38 PM   #33
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Re: Basement Slab Moisture


There has to be some sort of product out there that can achieve what you want. It's really just a long term temporary band aid though.
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Old 08-07-2017, 11:57 AM   #34
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Re: Basement Slab Moisture


dang a tough thing to diagnose over the web.

how confident are you that the weep tile goes all the way around the foundation?
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Old 08-07-2017, 06:53 PM   #35
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Re: Basement Slab Moisture


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dang a tough thing to diagnose over the web.

how confident are you that the weep tile goes all the way around the foundation?
100% confident. It is their footer form as well. Similar to the form a drain system. Full perf tile on both sides of footer.

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Old 08-07-2017, 07:01 PM   #36
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Re: Basement Slab Moisture


I'm just gonna talk out my ass for a minute or two. when the digger excavates & the footers are in and the weep tile goes down in place, you have circumcised that whole thing as a unit independent from surrounding soils?

yes?

so in theory, water CANNOT be coming from the perimeter.

That leaves flowing up from a deeper gravel bearing soil.

And I just checked - NW Ohio has some notable artesian springs.
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Old 08-07-2017, 08:03 PM   #37
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Re: Basement Slab Moisture


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Originally Posted by SmallTownGuy View Post
I'm just gonna talk out my ass for a minute or two. when the digger excavates & the footers are in and the weep tile goes down in place, you have circumcised that whole thing as a unit independent from surrounding soils?

yes?

so in theory, water CANNOT be coming from the perimeter.

That leaves flowing up from a deeper gravel bearing soil.

And I just checked - NW Ohio has some notable artesian springs.
That is what I think it really might be. Maybe not so much a well (although it could be) but ground moisture just below the footer tile. Stone wicks it up and then the slab wicks it up. Talked to Aquaflex today. They were very helpful and knowledgeable. May be a possible solution.

I am glad it is on my house so I can learn from it for future use...but I am not a unique foundation/slab type. I have to think a vapor barrier would have helped but thousands of homes in the area built before that was ever a thought or practice.

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Old 08-07-2017, 08:20 PM   #38
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Re: Basement Slab Moisture


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That is what I think it really might be. Maybe not so much a well (although it could be) but ground moisture just below the footer tile. Stone wicks it up and then the slab wicks it up. Talked to Aquaflex today. They were very helpful and knowledgeable. May be a possible solution.

I am glad it is on my house so I can learn from it for future use...but I am not a unique foundation/slab type. I have to think a vapor barrier would have helped but thousands of homes in the area built before that was ever a thought or practice.

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You can have artesian flow without it amounting to a well.

I couldn't abide by a sealer product myself.

There's a new airport terminal built over in Troy Michigan got torn down because a gravel vein 6' below the clay topsoil carried water into the crawlspace.

They excavated & built during summer when it was dry. When fall came and turned cold, the rain found its way under the footings, entered the buried HVAC pipes and steamed the terminal like a Swedish sauna.
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Old 08-07-2017, 08:30 PM   #39
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Re: Basement Slab Moisture


Yeah a sealer sounds good...but I think it would be another hail Mary. There is a product called Xypex that is used to waterproof underground tunnels and storage tanks. It sounds promising too...

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Old 08-07-2017, 08:40 PM   #40
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Re: Basement Slab Moisture


when you get all the tile up, are you going to be able to do some basic testing to see where the wet/wettest areas are?

Mind you, August is about the driest month of the year.

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