Lime – Wonderful stuff if you ask me. Use it as mortar, as wall plaster, or to form intricate moldings and decorations. It breathes, moves, often heals its own cracks, and does not encourage mold growth. The Gadsden House was built utilizing lime and as we move through the renovation process we are using it extensively.  

Here are some tips …

For historic Charleston renovation and restoration work lime is THE choice for real estate repair on these important buildings. Cement, on the other hand, should only be considered for “tanking ” (a waterproof membrane applied over a surface, preventing completely the entry of water – commonly used in basements) or structural strength.  

There are a number of stages in this work but it’s quite a simple process:

  • Remove anything that is crumbling – those parts that you can pull off with your hands.  Wooden lathe work underneath will probably remain fixed.
  • Secure original plaster around cracks using plaster tabs. These are like penny washers, large tab washers with a securing screw. They will pull the plaster back into the lathe work and help prevent later failure. Use only aluminum – steel will stain the walls permanently.
  • Use expanded metal mesh to back remaining holes and secure with aluminum screws.  Any old paper or flaking paint should be removed at this point.
  • First coat is “browning ” or brown plaster. It’s lime plaster with bonding and fixing agents added. It hardens by drying and can go on quite thickly and can be over-coated the next day.
  • Use “peel stop” (PVA Glue watered down) on firm paintwork to provide a bond for new top coat. 
  • Next step is applying two or more coats of finishing lime plaster – each should be no more than 1/8 ” inch thick. These coats contain aggregate to add bulk and provide a good bond. They harden on contact with carbon dioxide in the air so the coats must stay thin.
  • Last step, or “polish coat, ” is very fine lime putty.  It is polished by continually wetting and rubbing with a metal float until very smooth to the touch. 

Plaster walls will undulate a bit, this is quite normal in historic restoration work and adds the character missing from geometrically flat sheetrock.  The entire process will take about a week to complete with the drying/hardening periods but the warmth and depth of the final result is well worth the additional time and labor.

Tip – there is often a very small bulge in old walls where the plasterer could reach no higher up the wall and they switched to using a ladder.  We have gotten taller over the years!

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