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Repairing water damaged plaster

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wbgale

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After some heavy rains we had some water damage on interior plaster wall. After repointing the exterior it seems that the cause has been fixed and its time to repair the damage. We have an old brick house where the plaster appears to be directly applied to the interior masonry/brick, not over lathe.

Most of the repairs will be easy enough, but there are three spots (to the right of the window) where the damage was fairly bad and I could use some advice on repairing. Is there a specific way to fill the holes before applying new coat of plaster? That area crumbled away fairly easily and made a greyish sand-like substance.

 

Snoonyb

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That sound like mortar was applied as a base or brown coat before the plaster was applied.

As often as not a base or brown coat is applied to CMU walls to fill grout lines and any irregularities prior to a color coat being applied.
 

slownsteady

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I've never seen it in NJ, but in Pittsburgh, a lot of houses have walls that are more granular and stone-like....sort of reminds me of Wonderboard or Durock.
 

bud16415

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All the plaster around here from the 1800 thru 1950’s looked like that as a scratch coat. Looks sandy and like a rough unfinished concrete only softer.


With water damage sometimes it dries out and can be skim coated with finish plaster or even drywall compound depending on your skill level. Sometimes the base scratch coat gets softened by a lot of water and may want to fall off.


It is a little bit of a judgment call. Yours looks solid I would skim it and see how it holds up.
 
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