Restoration Register

Heritage plaster restoration in Ontario

The default answer to a cracked or sagging plaster ceiling in Ontario is a tear-out and drywall. It is almost always the wrong answer. A ceiling whose keys have broken off the lath can usually be re-secured from below with washers and adhesive, saving the ceiling and the cornice attached to it.

Heritage plaster work is flat work and ornament. Flat work is three-coat lime plaster on wood lath: re-keying loose fields, patching to original thickness so the surface stays flush, and finishing in a compatible mix rather than a hard modern skim that will craze along the boundary. Ornament is run cornices, ceiling medallions, corbels and enrichments, reproduced either by running a profile in place with a zinc template or by casting from a mould taken off surviving work. Only eleven specialists cover the province and seven of them are in the GTA, so outside Toronto this is a trade you book around rather than schedule at will.

What to ask before you hire

  1. Can this ceiling be re-keyed rather than replaced? Ask before anyone prices a tear-out.
  2. Will you run the cornice in place, or cast it? Both are legitimate. Stock polyurethane cornice from a catalogue is not restoration.
  3. What mix will you patch and finish with? A hard modern skim over soft lime plaster cracks along the joint within a couple of seasons.
Grant funding

Interior plaster is eligible where the designation by-law protects interior features, which many do not. Read the by-law, or ask municipal heritage staff what your designation actually covers, before planning the work around a grant.

Across Ontario

Region pages

All heritage service pages · Grants by municipality