GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Lime plaster over existing plaster and block

Lee Favro | Posted in General Questions on

Hi, I am working on a fire restoration. The home is concrete block on the exterior walls that were previously finished with plaster. It looks like the block had been coated with an adhesive, and I have had had to grind down to the scratch coat to remove the heat and soot damage. The “key” has been broken in many spots-which are now down to the block. There is some remaining wire, but only around window and door frames. I have ordered NHL and want to mix it with different grades on sand to produce two or three coats. My biggest question is can I get this new lime plaster to adhere to the previous plaster of unknown origin and block. I have heard of “knocking up” or ‘throwing'” a first coat- is this necessary? I have never plastered before. Any thoughts?

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.

Replies

  1. GBA Editor
    Martin Holladay | | #1

    Lee,
    I'm not a plaster expert. Perhaps a GBA reader will chime in to answer your question.

    In the meantime, here is a link to a web page with information that might help you: Cement Plaster Over Concrete Block Walls.

    As you might imagine, Portland-cement-based plaster (stucco) is more common than lime-based plaster. Here is another article that might help you: Make it Stick: A Common-Sense Way to Apply Stucco to Concrete Block.

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |