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Community and Q&A

Joint compound over poured concrete wall

Chris Sutherland | Posted in PassivHaus on

I would like to plaster then texture over old uneven concrete. I saw a product called plaster-weld. Can I use the plaster weld over the poured concrete wall and then just layer on coats of joint compound to get a textured even finish, then seal with a primer and finally paint it? When they formed up the basement walls years and years ago, they weren’t concerned with even finish. I can send you a photo if you need one. We get very little moisture in basement. Thank you in advance.

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  1. GBA Editor
    Martin Holladay | | #1

    It looks like PlasterWeld is appropriate for use over concrete walls. However, the intended finish over PlastWeld is plaster, not joint compound. So I don't know if there are any compatibility issues when joint compound is used over PlasterWeld. You might want to contact the manufacturer of PlasterWeld with that question.

    There are three other issues to consider:

    1. Is this basement wall insulated on the exterior? If not, then you probably want to install a layer of rigid foam insulation on the interior side of your basement wall before decided how to finish the wall.

    2. Is the basement wall really dry enough to proceed? (I'm not sure what you mean by "very little moisture.")

    3. Are you sure that you want to use joint compound as your finish surface? Joint compound is not a good finish material in damp locations.

  2. Chris Sutherland | | #2

    Martin, I think I'll go with the plaster weld and then plaster not joint compound. I emailed plaster weld company and they said it was okay to use over poured concrete. Our home is 100 years old...hence no insulation on outside of foundation. The only moisture we get in the area is humidity in the summer months but not bad. No mold or mildew on walls.

    My wife and I built a 3 sided wrap around covered porch with good eves. All water is diverted with eves. I see in other posts that Red Star plaster is a good product. The reason I was thinking of joint compound is that it dries slower and I can work it with a trowel with little difficulty. I have never plastered but assume it is similar to using joint compound. I tested an area using mortar and found it difficult to stick and couldn't get a good flat finish. Thanks for your help.

  3. Expert Member
    Dana Dorsett | | #3

    Finishing a basement without insulating the foundation first is usually the wrong thing to do, but it depends a bit on the exact climate. (In San Diego energy use and comfort issues related to basements are less of an issue than in Seault Ste Marie.)

    Beyond the energy & comfort issues, adding rigid insulation on the interior side mitigates a whole slew of potential paint-failure problems related to ground moisture wicking into the concrete. Before it's painted the concrete is highly vapor-permeable and ground moisture can dry toward the interior without problems. A layer of latex paint drops it from >40 perms to <5 foundation.

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