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My 125 year old house has old brick foundation which is exposed in the basement. I would like to plaster but don't want to do the complete three stage plaster job; the grout is deteriorated in many places and may be too fragile to attach wire lath. I have heard of a product that is a pre-mixed renovating plaster, but I don't know if such a product will work. Any suggestions?

Vickie Liles
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  • Just a thought: a lot of people really appreciate exposed brick. If it's structurally sound (assuming you repoint it) it may add value to the house. – DA01 Feb 03 '15 at 03:04

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This Old House's website advises getting a sample of the current plaster and mortar to s lab so you can get them accurately matched, if I remember correctly. They seemed to be saying that it was important that the brick and mortar be matched to each other, tho I'm not sure why..

keshlam
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    Because you can't re-point old lime-based mortar with modern cement-based mortar. – iLikeDirt Feb 03 '15 at 01:07
  • That much i understand; what i want is details. Chemistry? Expansion forces? Other? – keshlam Feb 03 '15 at 01:34
  • Portland cement should not be used for the repair or repointing of older buildings built in lime mortar, which require the flexibility, softness and breathability of lime if they are to function correctly. -[Wiki](http://en.wikipedia.org/wiki/Mortar_%28masonry%29) – Mazura Feb 03 '15 at 01:38
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    Right. Moisture in the wall is supposed to be able to escape through the lime mortar, which is softer than the bricks of that era. But modern cement is harder than old bricks, so the water trying to escape enters the brick instead, causing it to degrade and spall over time. – iLikeDirt Feb 03 '15 at 01:49
  • Gotcha. Tnx! On older walls, i'm told, the surface plaster was also part of the system, having its own effect on moisture balance... Someday I'll have to deal with this, but i've been afraid to go looking... – keshlam Feb 03 '15 at 02:04
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    Here's the video of that episode... https://www.youtube.com/watch?v=KlTzOFj6cME – Randy Feb 03 '15 at 03:52