Restoration Register

Heritage masonry cleaning in Ontario

Sandblasting a historic brick building is permanent damage sold as a cleaning service. It removes the fired outer skin and exposes the soft, porous body of the brick to water, and every water problem that building has afterwards traces back to that one afternoon of work.

Correct practice is the gentlest method that works, established by test patches in an inconspicuous area before the main work starts. In Ontario that generally means superheated low-pressure water systems, chemical poultices drawn against staining, and carefully selected proprietary cleaners, rather than abrasive blasting or a pressure washer at full trigger. What is being removed shapes the method: urban carbon crusts, biological growth on north elevations, efflorescence bleeding salts out of the wall, graffiti, and paint on brick that was never meant to be painted. Paint removal in particular can take the brick face with it. Only five specialists in the province do this properly, three of them in Toronto.

What to ask before you hire

  1. Will you do test patches first, and may I see them? Any competent heritage cleaner offers this before being asked.
  2. What pressure and what chemistry? Ask for numbers and product names. Abrasive blasting on historic brick is not acceptable at any pressure.
  3. What is causing the staining, and what happens about that? Cleaning growth or efflorescence without fixing the water source means paying twice.
Grant funding

Cleaning is eligible as part of masonry conservation under most municipal programs. Some ask for a method statement, and the test patch documentation usually satisfies that requirement.

Across Ontario

Region pages

All heritage service pages · Grants by municipality