Damp crawl space

[brogsie]

My partially completed house has a crawl space on 10 feet because the septic tank is ten feet from the foundation.
I pulled up the plywood sub-floor in the bathroom over the crawl space. Underneath is a slab on grade. Floor framing is 3 inches off the slab on PT sills.
6 inches of insulation in the floor. When I pulled the insulation out it was musty and quite damp. The house is on the coast of MA a very humid area.
How can I stop this moisture? I have a couple of ideas.
1) Seal the slab with a masonry sealer.
2) Ventilate the space into the full basement using a fan pulling out and one pushing in. Full basement needs a dehumidifier running all summer.
3) Insulate on top of slab with 2 inch foam insulation panels.

Any help would be appreciated.

 

[vvvv]

tape & seal a small piece of polyethylene plastic on slab to find whether humidity comes from the ground or from the air above it, though it seems 2" foam would work. consider a heat pump water heater to replace the dehumidifier in the cellar.

 

[LLigetfa]

I vote #3.

3) Insulate on top of slab with 2 inch foam insulation panels.

I'd also consider spray-in-place foam insulation like WallTite.

 

[smokinj]

My crawlspace was full again this A.M. I have the spray foam in as thick as we could get it....The problem we are haveing is its coming up through the ground its self we are over 7 in's above the normal for the month and many shots of 2hour rains in the 2-4 inchs sump pump is the only way I know to keep the ground water out that's been thrown my way....Cant even get the kayaks out and its June I have never seen this this kind of rain....Reminds me of the Forest Gump movie and all the rains he goes through.
My water table is high are well hits water at 8 foot.

 

[oldspark]

My crawlspace was full again this A.M. I have the spray foam in as thick as we could get it....The problem we are haveing is its coming up through the ground its self we are over 7 in's above the normal for the month and many shots of 2hour rains in the 2-4 inchs sump pump is the only way I know to keep the ground water out that's been thrown my way....Cant even get the kayaks out and its June I have never seen this this kind of rain....Reminds me of the Forest Gump movie and all the rains he goes through.
My water table is high as well are well hits water at 8 foot.

Same thing here in Iowa over 5 inches this weekend with flooding every where.

 

[smokinj]

My crawlspace was full again this A.M. I have the spray foam in as thick as we could get it....The problem we are haveing is its coming up through the ground its self we are over 7 in's above the normal for the month and many shots of 2hour rains in the 2-4 inchs sump pump is the only way I know to keep the ground water out that's been thrown my way....Cant even get the kayaks out and its June I have never seen this this kind of rain....Reminds me of the Forest Gump movie and all the rains he goes through.
My water table is high as well are well hits water at 8 foot.

Same thing here in Iowa over 5 inches this weekend with flooding every where.

looks like we have a 5-6 days clear now. My kayaks are strap and ready for Thursday should be fine by then if we don't get another drop...wishful thinking.

 

[bjkjoseph]

my crawl space is wet too..i did part of it with closed cell spray foam,with a antimicrobial additive.it was so expensive i didn't finish...but its worth the cost.

 

[brogsie]

Thanks for all the ideas.

Joseph, How much did the spray foam cost?
Did you spray it on the slab?

 

[begreen]

It helps to determine the cause of the moisture. If it is a high-water table that is a tough one. But often the issue is with gutter systems that don't drain away from the house. If that is the issue, extend the drainage away from the foundation. Or the house is on a slope and is getting the run off. A proper french drain can help with that problem. At the very least there should be a heavy vapor barrier down on the crawlspace floor.

A very common issue is condensation. The cool air under the house causes the very humid summer air to condense under the house. If this is determined to be the cause, turning this space into a conditioned space can be a solution.

http://www.buildingscience.com/docu...space-construction-performance-and-codes/view
http://www.buildingscience.com/docu...-resistant-construction/view?searchterm=crawl

 

[bjkjoseph]

i forget the exact price,i used foam it green...there pretty much all about the same price..foam it green had free shipping...i sprayed it on the underside of the floor..i would not spray the slab.

 

[smokinj]

cost me 1000.00 bucks I rember every penny well worth it but still will not stop ground water!

 

[oldspark]

Ground water is a different can of worms altogether.

 

[smokinj]

Ground water is a different can of worms altogether.

Yes it is and the first year I have ever seen it (very wet june corn is chest high) the foam spray has done evrything I need out of it....I was confuse at first where the heck mine was coming from.....

 

[brogsie]

Thanks for the thoughts.

I taped plastic on the floor and it was dry. After pulling out the insulation the slab dried out.
I'm pretty sure it's condensation. The slap was cold compared to the air. I think I will use the rigid foam insulation on the slab
then insulate between the joists. I will let you know how I make out.

 

[webbie]

I have a very damp crawl in RI and did my research - here is how I am gonna fix it.

1. Spray foam on underneath of floor - this will stop most moisture from attacking floor and seeping up through walls.
2. Install special crawl space dehumidifier - about $700-$1000.

I checked the humidity level in the crawl and it is 80% plus - that would be harmful to the construction in the long run. In fact, I am getting some staining of baseboard an bubbling of paint (small amounts)....so I am definitely going to take action. The water table is very high, so attempting to fix it in other ways is unlikely to work.

 

[begreen]

Put a hull on it Craig. Ya need another boat.

 

[webbie]

That sound like the advice we used to give for certain stove models, except that was "tie a rope around it and make it an anchor"....

My customer service guy always told a story about the worst service he ever got at Sears...he bought tires there, and when one failed brought it back. They told him to tie a rope around it and make a swing......

On the more ambitious end of things, perhaps I could sell the water I squeeze out as "distilled".....?

 

[oldspark]

Do you run drain tile in that part of the country?

 

[webbie]

Do you run drain tile in that part of the country?

Oh, this has lots of draining, including electric pumps which pump to a drain field 100 feet away.
Problem is that the water table rises so high that no man made device can keep it down - during the crazy spring rains we had about a foot of water on top of the gravel down there....still 2 feet below the joists, but definitely humid.

In short, there is no regular mechanical way to stop it - too much water and too much pressure....glacial rock in the area, etc.

That's why I think falling back and playing defense is the best move.......the dehumidifiers are specially made for crawls and I will hang it between the floor trusses and drain it to one of sump pits.

Seems like the story of my life is fighting water in basements and crawls.

 

[oldspark]

They drain tile everthing in Iowa and it seems to work well, you maybe are just dealing with a cool cement floor and condensation because of the ground water cooling effect. Is this the case?

 

[webbie]

We have springs just popping up out of the ground around us due to pressure.....
From what I can determine, the regular ground water (or an underground creek) is about 1 foot below the level of the gravel (no slab, just gravel) crawl floor. When the rains come that water table rises up to almost even with the gravel or even above it.

I suppose we could put in drains and then build up the gravel and pour a slab, etc. - but that would cost a lot more and then access to the crawl will be really tight - as it stands I can go under there pretty well and crawl around.

I read all the papers on how to seal a crawl and drain it, but my gut tells me it won't work - that I am trying to hold back too much pressure. So I figure the foam and the dehumidifier will do 95% of the job - and if the water rises in the crawl once or twice a year, so be it. There are no systems or electric at that level, so the water can just come and go.

 

[woodsmaster]

Make sure to check for post powder beetles etc. before you foam. they love damp wood and after foamed near impossible to treat.

 

[oldspark]

I dont think you want to seal it, just drain it but it sounds like you already have drain tile now correct? that will the water table.