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Old 12-16-2008, 12:10 PM
 
Location: Baywood Park
1,634 posts, read 6,434,473 times
Reputation: 704

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I'm having issues with dampness around certain parts of the house. Around the room corners . Seems the the slab foundation is wicking up moistutre. Carpet feels damp, moisture midew smell. I want to remove the carpet and pad and seal the slab. I've already applied a product to the exterior below grade. It's helped, but not completely. It was called liquid rubber. Any product suggestions? or ideas?
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Old 12-16-2008, 01:46 PM
 
3,020 posts, read 25,051,857 times
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Default Can it help? Well sort of.......

That whole idea of concrete sealers is a bit of a snake pit.

Lots of claims, scams and some snake oil sales.

Understand the basics up front.

Good concrete will not pass water if it is of an excellent grade and strength rating. Most home contruction is usually of a crap grade of concrete, so there is the core problem. The problem starts in the initial selection of the concrete, at the root of the problem in not enough cement in the mix. Also understand concrete is a chemical function, the process starts as soon as it is mixed and continues in theory forever. Most of the reaction (~95% +) occurs in the first 28 days.

So once this crap concrete mix is in place then what? Well concrete can be sealed. Usually that is best done within the first day after pouring the concrete. Has two functions, it prevents water evaporation, gives the concrete a better chance at a better cure in those first 28 days and does give some measure of surface sealing. This tends to prevent water penetration both ways.

After the concrete is gone thru the 28 day cure period, then all bets are off as to the effectiveness of any product. This can be where the snake oil process comes into play. What exactly are the claims, what exactly is the process involved, how deep is the penetration of any type of sealer?

Beware of claims of vast deep penetrating type sealers. Also beware of claims that the sealer somehow interacts and becomes part of the concrete. In fact a number of sealers may have negative impacts on concrete. At best there may be some shallow penetration (maybe 1/8" or so, something down into about the "Cream Layer" of the concrete) and that might provide some water sealing ability for some period. Just painting the concrete surface might provide about the same protection.

Probably any type of paint, sealer, even something like a poly could be used. The question being can the surface treatment flake off, what is its working life? The commercial products sold might have some effectiveness, again the question being what are the claims, you do stand a chance of over paying for whatever it is.

Then you have that 64 million dollar question of what happens if you have the real crap concrete mix that is super poreous and you slap on some mircle juice and it really does deeply soak into the core of the slab. In the end, it is awfully difficult to improve concrete once it is mixed and poured.

I might seal it with something but would sure not want to pay a bunch for the honor of doing so. Beware of them slick talking fellows, lots of folks are hawking something.
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Old 12-16-2008, 03:09 PM
 
21,373 posts, read 64,178,437 times
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Remember that in high humidity situations, moisture may be condensing on cool concrete and other surfaces from the air. Even dry basement spaces often have dehumidifiers to prevent mold problems.

Intrusion of ground moisture can be an issue. Sealing the top layer can be ineffective if water pressure is enough to lift the sealer off the concrete. I once owned a house with a severe water intrusion problem. The previous owner had eventually laid poly on the existing basement floor, and poured a fresh sheet of concrete on top of that, incorporating gutters around the perimeter. It worked in most areas.
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Old 12-16-2008, 07:24 PM
 
3,020 posts, read 25,051,857 times
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Default Not all concrete is the same.......

The other thing most peeps do not realize is not every pour of concrete is the same. Including those mixes that might have about the same specs. Lots of variables influence the final slab and how it performs. Mix, amount of time before it is poured, how handled, temperature, on and on.

You can have a totally waterproof cement. They even make boats out of the stuff, more accurately called ferrocement. Usually it is just a sand / cement mix but the mix is very critical. Even the sand has a special blend of various sand grains. That all so goes for more normal concrete too. The mix can be critical. One area that you can run into in houses is the concrete companies now recycle materials. Things like old cement walls, sidewalks, whatever gets busted up, ground down to make new sand / gravel. Reused in a new pour. Great idea but it must be closely monitored. Easy to get a bad mix. Many times way to much fines, dust and micro-particles get included, can be a super bad mix. The advantage is for certain projects like large sidewalk projects over many acres / square miles there is a huge cost advantage. If you get a lot of fines with a normal batch of concrete it can be pretty weak stuff, will have lots of other negative character traits too.

But I would avoid most of that type of mix for a house. Knowing what happens, some contractor saved a few bucks. The slab in every house is not the same, what Uncle Harry got may not be close to what you got.

That may be the hidden flaw in many of the manufacturer claims for sealers or anything to do with concrete. Some sealers may work well on a pretty good mix, not at all on a garbage mix. Of course the better mixes may not need any sealer.

A lot of this is a game of expectations and salemanship based around a less than known situation as far as your own situation or results might be.

So ten peeps might all use the same sealer stuff and all their results could be wildly different, they didn't all start with the same conditions. There is that golden rule of thumb. Once concrete is poured, you can't do much to make it better, that all had to start back at the cement plant with what went into the truck.
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Old 12-17-2008, 07:52 PM
 
Location: NW MT
1,436 posts, read 3,152,262 times
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Quote:
Originally Posted by CA central coast View Post
I'm having issues with dampness around certain parts of the house. Around the room corners . Seems the the slab foundation is wicking up moistutre. Carpet feels damp, moisture midew smell. I want to remove the carpet and pad and seal the slab. I've already applied a product to the exterior below grade. It's helped, but not completely. It was called liquid rubber. Any product suggestions? or ideas?
Cosmic and Harry offer excellent info, for Cosmic especially if just starting out with a new project. But for you all the explanations probably mean nothing to you now. To solve your problem I agree, stay away from sealers, they are not a real fix. If you want to really fix the problem now, after the fact, keep the water from getting to and under the foundation in the first place !

Make sure gutters and downspouts are working properly moving water away from the house and if not already existing, put in some foundation drain tile with gravel all the way up to grade. This will allow water to be removed away from the foundation before ever coming in contact with it. If you have natural fall for water to move away from the foundation via the tile then great, all the better. If not, then you are looking at a sump pump situation.

Bottom line... keeping water away from the foundation in the first place will eliminate 99% of foundation moisture issues.
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Old 12-19-2008, 08:13 PM
 
Location: Johns Creek, GA
16,181 posts, read 60,079,868 times
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It's not about the concrete- it's about the water/moisture itself. As Stephan stated, keeping water away from the slab is the best defense.
And I suspect a couple of other possible issues- how is the grade away from the house? The standard code requirement is 6"/10'. 6" of fall, for 10' of run (minimum). The other is a vapor barrier. Code mandate- a 6mil (minimum) poly will cover the effected ground area where the concrete will be poured. In other words, there should be a plastic vapor barrier between the earth and the concrete slab.
The other thing to remember- it's easier to stop water infiltration from the source side and not the side your trying to keep dry.
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Old 12-20-2008, 08:55 AM
 
458 posts, read 2,140,303 times
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A concrete sealer will not be very effective with your issue. In fact, a concrete sealer will probably not even set up with the water vapor present. You will need to deal with the water itself to solve the problem. Sounds like you already installed a waterproofing product on hte exterior side of your foundation? That would be a good start. Installing a foundation drainage system should be your next step if the problem is persisting - this is done by installing a drainage tile around the perimeter of your foundation. Water captured by the drain tile is then either daylighted if gravity allows, or conveyed into a sump pump to pump the water away.
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Old 12-23-2008, 07:10 AM
 
Location: Baywood Park
1,634 posts, read 6,434,473 times
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It's 60 yr. old house. No vapor barrier. The grade is probably not exactly code, but I'm built on sand, water drains easily here.
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Old 12-25-2008, 06:19 PM
 
93 posts, read 247,119 times
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Quote:
Originally Posted by CA central coast View Post
I'm having issues with dampness around certain parts of the house. Around the room corners . Seems the the slab foundation is wicking up moistutre. Carpet feels damp, moisture midew smell. I want to remove the carpet and pad and seal the slab. I've already applied a product to the exterior below grade. It's helped, but not completely. It was called liquid rubber. Any product suggestions? or ideas?
hey ca coast, i had a serious water issue in my basement and used a product called UGL "drylock extreme"... worked like a charm! i put it on liberally. my basement is tiny 10x10...small cottage i rent. if memory serves, i went thru 4-5 gallons to do the floor and walls up to the ceiling. you may not need to go to the ceiling if your grade is below that level.

KILZ products may also work to encase mildew but only the ugl will keep water from seeping into the block/mortor from outside. both products can be purchased at pretty much any hardware and/or home improvement store. i also agree a dehumidifier would help you out a lot... i have one and it's amazing how quickly the 2 gallon bucket will fill on some days... also helps to "pull" the disgusting mildew smell from the room. good luck to you. have a good one.
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Old 12-27-2008, 11:13 AM
 
Location: Baywood Park
1,634 posts, read 6,434,473 times
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A dehumidifier will pull that musty smell out? My carpet and pad smells musty in areas, but I don't see any mold at all in the carpet or pad. It just stinks. Should I try to save it or toss the carpet and pad? Does musty mean mold? or just that it got wet and now stinks? I want to be on the safe side.
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