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grubby_az

mortar joints shadowing through plaster

I am skim coating a brick wall with strongly raked (square recessed) joints. It used to be an exterior wall. After two+ coats of premixed drywall mud, the joints are still telegraphing through. I'm using a 12 inch knife diagonally and it looks like I will be doing four or more coats.

Is there a faster way (fewer coats) I can try on the next wall I get to? There's always excessive texturing, but we want a relatively smooth finished wall.

Comments (4)

  • sombreuil_mongrel
    9 years ago

    Hopefully this disaster is in a closet or someplace like that. When you dive in without checking things out first, you can get messed up. To obtain a proper smooth wall surface over brick takes three-coat plaster work. At this point you really can do nothing but put drywall over it. But if there is any kind of moisture issue with the brick, that won't work very well either. You should use a moisture barrier, insulation and furring strips (if not full studs)
    Where did you hear that you could do this?
    An exterior brick wall that is still thermally-bridged to the outside is going to bring cold inside at the corners. That cold masonry wall is going to be a moisture magnet in the winter, as moisture condenses on it from the indoor air. Moisture condensing on a mudded surface is going to induce paint and mold problems. Had you used stucco or three coat plaster, you would not have introduced a mold-fest, because those products are mineral, and provide no food for mold, unlike drywall mud, which contains glue and other additives that provide a food source.
    Casey

  • grubby_AZ Tucson Z9
    Original Author
    9 years ago

    As said previously, this is an interior wall. Drywalling over an interior brick wall is overkill and would mean re-trimming everything, also to be avoided. Assuming mold on an interior wall is a huge reach. Moisture condensation on an interior wall in Arizona under air is unlikely. You did answer my question, but I don't understand the baggage.Why are you getting righteous?

  • snoonyb
    9 years ago

    " but I don't understand the baggage.Why are you getting righteous?"

    Its a honest response, which is an expression of frustration.

    Frustration from those of us who are willing to part with advice, we have learned through years learning the complexities of the construction industry.

    Frustration at those who come here after the horse has left the barn, been featured on the menu of a local restaurant and the balance unconsumed, donated to 2nd harvest.

    Asking how to fix, what may have been avoided, had they stopped by before.

    To your credit, you are not looking for absolution, just advice.

  • lazy_gardens
    9 years ago

    After two+ coats of premixed drywall mud, the joints are still telegraphing through.

    That's your problem ... drywall mud is meant for drywall joints and skim coats on smooth surfaces.

    Next time you do this, apply standard metal lath and do a 2 or 3-coat stucco finish. It only sounds like more work.

    ADDING: Start with a bonding agent, then apply the mesh. On the first coat, you have to really PUSH the base mud through the mesh into the cracks. "Scratch it" for better bonding with topcoat.

    Keep it damp while it cures a couple of days.

    Dampen it and apply your finish coat, smoothing it out all nice and purty.

    This post was edited by lazygardens on Tue, Jul 29, 14 at 12:53