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  1. #1
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    Jan 2012
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    Default condensation on basement walls- help

    My basement walls are cinderblock, 60 yr old Cape Cod in PA. Contractor sprayed waterproofing material like, drylock, on walls. Now walls have condensation and the spray stuff is chipping off, leaving behind sand. How can I patch this or is it a bigger problem than I antipate? The walls underneath seem sound. Please help.

  2. #2
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    Default Re: condensation on basement walls- help

    do you see more condensation when it's raining outside?

  3. #3
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    Aug 2007
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    Portland, Oregon, formerly of Chicago
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    Default Re: condensation on basement walls- help

    Are you really seeing condensation? Condensation is when relatively high humidity meets a cool surface.
    Or is this moisture seeping in from the outside?

    If it is condensation, you might want to invest in a dehumidifier. You could also heat/air-condition this area by putting air returns and vents down there, assuming you have a hot air system. If you have hot water or steam, you can add a radiator to bring the heat up a little. Some kind of fan moving air will also help fight condensation.

    If it is moisture from the out side, you might want to check the grade outside the walls and also where downspouts are dumping out. There are other things that can be done to alleviate foundation moisture, but they can get expensive real fast!

    Dry-Lock , if applied properly, is usually fairly effective. It is not sprayed on. It is brushed on with two heavy coats worked deep into the texture of the cement or cement blocks. If you can sc**** the old stuff off, you might want to try the Dry-Lock, at least make a test area to see if it helps. However, Dry-Lock only guarantees its product if put directly on the bare cement or block.

  4. #4
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    Jan 2008
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    Default Re: condensation on basement walls- help

    It sounds like the contractor sprayed block filler, not Dry-lock. Block filler looks similar but is not meant to bond to wet surfaces. When it gets wet you can pull it off in strips or chunks and it will have a sandy residue under it. It's that sand you mentioned which makes me wonder if the walls were prepped correctly. At mortar joints you may see sand, but if it's everywhere this guy didn't prep the wall correctly before coating it. Coupled with the spraying instead of rolling I'd say this contractor was too much of a in a hurry to get paid. Spraying and backrolling is fine to cover block, but spraying alone doesn't cut the mustard- you want to force the coating into the block's pores.

    Whatever you've got, you're going to need to do two things. First is to keep as much water out of the wall as possible from the outside- that's really where waterproofing belongs anyway. Then after everything is as dry as it will get you need to remove as much of the old coating as possible. With some luck this will be aided by the poor prep-work. Finish with Dry-lock worked into the block with a roller, then go with the paint color you want to see.

    Sadly most underground block basement walls were never intended to be used as a finished room so waterproofing on the exterior side was not done or was done poorly when the structure was built as a cost-cutting measure. The quick-and-dirty way of determining how well the walls are sealed is to look for efflorescence on the block- a whitish powder which is the lime leaching out of the cementitious material where it gets wet. If you see much of that you're better off not trusting the wall to be waterproof.


    I never recommend block as a finished basement wall surface; you're a lot better off slatting them then hanging drywall using a moisture barrier under the pressure-treated slats. Always use the proper drywall product here, the interior grade stuff won't last as you still have a lot of humidity present in a basement. Styrofoam insulation between the studs is a good idea but optional. This has the added benefit of creating a cavity to run wiring and plumbing through behind the wall for a better finished appearance. Ask TOH did an episode on how to do this- check it out!

    Phil

  5. #5
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    Jan 2012
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    Default Re: condensation on basement walls- help

    Quote Originally Posted by Paragon42 View Post
    do you see more condensation when it's raining outside?
    No, beads of moisture always seem to be visible. They don't seem to be "dripping", but you can see them on the surface of the white finish. It's wet to the touch, but also feels a bit oily, not like plain water. If you were not looking for it, you probably would not notice the moisture.

  6. #6
    Join Date
    Jan 2012
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    5

    Default Re: condensation on basement walls- help

    Quote Originally Posted by ordjen View Post
    Are you really seeing condensation? Condensation is when relatively high humidity meets a cool surface.
    Or is this moisture seeping in from the outside?

    If it is condensation, you might want to invest in a dehumidifier. You could also heat/air-condition this area by putting air returns and vents down there, assuming you have a hot air system. If you have hot water or steam, you can add a radiator to bring the heat up a little. Some kind of fan moving air will also help fight condensation.

    If it is moisture from the out side, you might want to check the grade outside the walls and also where downspouts are dumping out. There are other things that can be done to alleviate foundation moisture, but they can get expensive real fast!

    Dry-Lock , if applied properly, is usually fairly effective. It is not sprayed on. It is brushed on with two heavy coats worked deep into the texture of the cement or cement blocks. If you can sc**** the old stuff off, you might want to try the Dry-Lock, at least make a test area to see if it helps. However, Dry-Lock only guarantees its product if put directly on the bare cement or block.
    I have a dehumidifier down there.Downspouts are not an issue, but the grade outside may be something to look into. I know this wasn't "drylock", but what I meant was it was some kind of "waterproofing" spray that was applied. When I look in my sub-cellar, which was not sprayed, the bare block looks fine. I appreciate your assistance.

  7. #7
    Join Date
    Jan 2012
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    5

    Default Re: condensation on basement walls- help

    Quote Originally Posted by Mastercarpentry View Post
    It sounds like the contractor sprayed block filler, not Dry-lock. Block filler looks similar but is not meant to bond to wet surfaces. When it gets wet you can pull it off in strips or chunks and it will have a sandy residue under it. It's that sand you mentioned which makes me wonder if the walls were prepped correctly. At mortar joints you may see sand, but if it's everywhere this guy didn't prep the wall correctly before coating it. Coupled with the spraying instead of rolling I'd say this contractor was too much of a in a hurry to get paid. Spraying and backrolling is fine to cover block, but spraying alone doesn't cut the mustard- you want to force the coating into the block's pores.

    Whatever you've got, you're going to need to do two things. First is to keep as much water out of the wall as possible from the outside- that's really where waterproofing belongs anyway. Then after everything is as dry as it will get you need to remove as much of the old coating as possible. With some luck this will be aided by the poor prep-work. Finish with Dry-lock worked into the block with a roller, then go with the paint color you want to see.

    Sadly most underground block basement walls were never intended to be used as a finished room so waterproofing on the exterior side was not done or was done poorly when the structure was built as a cost-cutting measure. The quick-and-dirty way of determining how well the walls are sealed is to look for efflorescence on the block- a whitish powder which is the lime leaching out of the cementitious material where it gets wet. If you see much of that you're better off not trusting the wall to be waterproof.


    I never recommend block as a finished basement wall surface; you're a lot better off slatting them then hanging drywall using a moisture barrier under the pressure-treated slats. Always use the proper drywall product here, the interior grade stuff won't last as you still have a lot of humidity present in a basement. Styrofoam insulation between the studs is a good idea but optional. This has the added benefit of creating a cavity to run wiring and plumbing through behind the wall for a better finished appearance. Ask TOH did an episode on how to do this- check it out!

    Phil

    Thanks for all the excellent info. It's a basement, that's all, not finished. A floating slab was created to keep out excessive rain water with a sump pump in 2000. The guy sprayed this white junk on as "extra protection". Where the white, sprayed-on material is falling/chipping off, the block underneath looks sound, feels cold. It does not feel wet, & I see no visible moisture on that surface. The beading is on the white surface on top of the block, and yes, there is sand between the two. If you touch the moisture, it feels wet, but slight oily. That makes me think this is something leaching from the white surface. There is a sub-cellar that has not been finished, & that block looks fine. Also, let me mention, this chipping is occurring mostly at the same level on the wall,maybe at the watertable? I don't see the efflorescence on the block. I know what that looks like.

  8. #8
    Join Date
    Oct 2012
    Posts
    5

    Default Re: condensation on basement walls- help

    I'm not a big fan of the "waterproofing" interior coatings, on the plus side they look great when applied, they go on nice and thick and even out the surface but they have a limited life span, usually around the three year mark before they start flaking and falling off the wall. The issue is the water and minerals from the backside are still pushing, if the concrete can't stop it the coating won't. Another issue is the concrete blocks (and mortar) when exposed to long term moisture turn to sand and crumble.

    Something that hasn't been mentioned is the air-circulation in the basement. The area should be closed off most of the time, open windows and doors allow warm humid air into the basement area which is normally colder and can't hold this humidity. The air will condensate on the walls giving you the drips.

  9. #9
    Join Date
    Oct 2012
    Posts
    29

    Default Re: condensation on basement walls- help

    Inadequate ventilation can also lead to condensation, may be the humid air is not getting the way to go out is collected on the coolest surface leading to moisture. You can re-plaster the wall with waterproof plaster which acts as a barrier to moisture.

  10. #10
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,381

    Default Re: condensation on basement walls- help

    I think you do have condensation and you have always had condensation. Without the "waterproofing" material, the blocks absorbed the moisture, as the bare areas are doing now. The "waterproofing" is preventing the moisture from being absorbed so it beads up on the surface.

    Waterproofing of the basement block walls should be done on the outside, and since you don't seem to have a problem where the waterproofing is missing, I'd guess that it has been done and is still in good shape. Properly waterproofing the inside of the blocks will help them last longer.

    The only way to stop the condensation is to reduce the humidity in the air in the basement. If you have a laundry room in the basement, chances are the relative humidity in the basement is pretty high, especially on laundry days. Since part of the basement walls are exposed to the outdoor temperature and the basement is not heated, then the basement walls are cold enough to be below the dew point for the relative humidity in the room, so condensation will form.

    A dehumidifier would be your best bet here. Even then, you may still see some condensation on the walls.

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