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Old 08-02-2010, 01:55 PM   #1
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Waterproofing CMU with Thoroseal


Before I install foam insulation in the basement and frame out new walls, I want to coat at least part of the wall with Thoroseal. The trouble is, the CMU block has been painted with some sort of light blue paint. I noticed the basement slab has been coated with the same sort of paint.

I have patch of wall where the paint has flaked away due, as far as I can tell, to water intrusion. The only other place I've had any trouble with water intrusion is at the joint between the slab and the block.

How can I chemically strip the paint without creating a gummy mess that fills the pores of the block? Should I apply the Thoroseal just to the portion of the wall where the paint is flaking away?

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Old 08-02-2010, 02:56 PM   #2
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Waterproofing CMU with Thoroseal


You want the wall to let the moisture in to dry to the inside, not stop and divert it somewhere else finding another entry point. (Between wall/slab, harder to fix). That is the whole purpose of the foam (besides thermal break), 2" thick minimum, to allow the water through slowly.
http://www.buildingscience.com/docum...gs?full_view=1

Be safe, Gary

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Old 08-02-2010, 03:31 PM   #3
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Waterproofing CMU with Thoroseal


Thoroseal is a great cement-based water poofing/water resisting coating that has been used for decades on commercial, civil and and idustrial applications and restoration of scultures, details, etc. Not normally a highly promoted or advertised DIY product. Two coats with the pror application and mixing (with an additive) is probably the best material for an interior use (and even better on the exterior or wet side).

Unfortunately, it works best on a clean concrete surface that is dampened before application, but is just as bad a Dry=Lok or other paint type materials when applied over a contaminated face. Because of this it is probably not the best for your application, but a latex additive (Acryl 60 or similar) will make it as good as the others, but not as good as possible.

You will still have to address the joint between the wall and the slab, where much of the problems seem to occur. I hope you do not have the formed joint in the top of the slab that was common at one time to collect the water that the contractor knew would come in from poor planning and techniques.

Dick
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Old 08-02-2010, 03:32 PM   #4
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Waterproofing CMU with Thoroseal


Quote:
Originally Posted by GBR in WA View Post
You want the wall to let the moisture in to dry to the inside, not stop and divert it somewhere else finding another entry point. (Between wall/slab, harder to fix). That is the whole purpose of the foam (besides thermal break), 2" thick minimum, to allow the water through slowly.
http://www.buildingscience.com/docum...gs?full_view=1

Be safe, Gary
Gary,

I'm confused. That article seems to say that I should put no thicker than 1" foam on the wall?
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Old 08-02-2010, 03:39 PM   #5
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Waterproofing CMU with Thoroseal


you're almost a n-bor seeing as i lived in allamuchy ( panther valley ) & we work'd fron bergen to ocean doing bsmt wtrproofing

thoroseal on the interior wall's not a good idea as, even IF it were permanent, the intruding wtr will still be penetrating your block foundation wall,,, now in atl, we're replaced several fnd walls that simply collapsed due to unmanaged wtr damage.

if you must, mechanically remove the paint - aurand makes a great little deck scaler which works fine on block,,, apply anything to paint which hasn't flaked off YET isn't a good bet to me.
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Old 08-02-2010, 03:50 PM   #6
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Waterproofing CMU with Thoroseal


Quote:
Originally Posted by concretemasonry View Post
Thoroseal is a great cement-based water poofing/water resisting coating that has been used for decades on commercial, civil and and idustrial applications and restoration of scultures, details, etc. Not normally a highly promoted or advertised DIY product. Two coats with the pror application and mixing (with an additive) is probably the best material for an interior use (and even better on the exterior or wet side).

Unfortunately, it works best on a clean concrete surface that is dampened before application, but is just as bad a Dry=Lok or other paint type materials when applied over a contaminated face. Because of this it is probably not the best for your application, but a latex additive (Acryl 60 or similar) will make it as good as the others, but not as good as possible.

You will still have to address the joint between the wall and the slab, where much of the problems seem to occur. I hope you do not have the formed joint in the top of the slab that was common at one time to collect the water that the contractor knew would come in from poor planning and techniques.

Dick
I believe I have tar on the exterior at this point. I'm not sure how easy that would be to remove. I'll be digging down to see what sort of perimeter drain I have. I'll probably end up putting in one those EZ-drain tiles next to the footing.
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Old 08-02-2010, 03:57 PM   #7
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Waterproofing CMU with Thoroseal


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Originally Posted by itsreallyconc View Post
you're almost a n-bor seeing as i lived in allamuchy ( panther valley ) & we work'd fron bergen to ocean doing bsmt wtrproofing

thoroseal on the interior wall's not a good idea as, even IF it were permanent, the intruding wtr will still be penetrating your block foundation wall,,, now in atl, we're replaced several fnd walls that simply collapsed due to unmanaged wtr damage.

if you must, mechanically remove the paint - aurand makes a great little deck scaler which works fine on block,,, apply anything to paint which hasn't flaked off YET isn't a good bet to me.
Allamuchy is a nice area. I hope you've adjusted well to the heat and the city life down in Atlanta.

So, I guess I'll leave the walls painted and retar the outside or something since achieving a clean surface on the exterior will be difficult.
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Old 08-02-2010, 04:29 PM   #8
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Waterproofing CMU with Thoroseal


code calls for a .003" coating of dampproofing mtl ( asphalt emulsion avail in 5gal pails at any apron store,,, you can't buy ' tar ' & apply it manually w/brushes,,, that needs to be applied hot,,, what you CAN buy is fiber reinforced roofing cement & trowel it onto a clean foundation wall w/plastic trowel,,, wear VERY old clothes & get gloves that extend up to your elbows careful w/the excavation so you don't get buried alongside your footer.

go onto my our/site & look at the diagram
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Old 08-04-2010, 09:30 PM   #9
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Waterproofing CMU with Thoroseal


Quote:
Originally Posted by GBR in WA View Post
You want the wall to let the moisture in to dry to the inside, not stop and divert it somewhere else finding another entry point. (Between wall/slab, harder to fix). That is the whole purpose of the foam (besides thermal break), 2" thick minimum, to allow the water through slowly.
http://www.buildingscience.com/docum...gs?full_view=1

Be safe, Gary
Gary, I noticed you mention leaks between the wall and the slab being difficult to fix. I had water intrusion wall-slab joint, but I think it was due in large measure to drainage issues that I addressed. Just to make sure water is being diverted away from the house, I'm going to dig up the drain tile and replace it. If I apply spray foam where the rigid foam meets the slab, will I be able to repel water that gets past my perimeter drain?
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Old 08-05-2010, 12:04 PM   #10
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Waterproofing CMU with Thoroseal


I think there are better choices than spray foam for this application. We have two resident concrete experts here, let's see what they recommend...

Be safe, Gary
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Old 08-05-2010, 01:01 PM   #11
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Waterproofing CMU with Thoroseal


I'll be interested to hear what the concrete guys have to say.

I haven't had a problem since I cleared out some leaves and some boards that were stacked right next to the house, but I'm not certain that was the cause. Whatever the case, water penetration in a carpeted area will not be welcome. I'm hoping the drain tile will prevent any future issues, but I'd also like a fail-safe measure and the gap. The Radonseal folks suggest using a grinder to cut a channel at the wall-floor intersection for epoxy. That idea sounds like a messy pain in the neck.

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