How to Clean Masonry Before Coating or Repair

Get concrete, brick or block down to a clean, sound, dry surface so a coating, sealer or patch bonds. Coatings bond only to the surface they touch.

What you need

Identify what is on the surface: loose material, efflorescence, oil or form-release, or biological growth. Most surfaces have more than one.
Mask aluminum and stainless trim. Plan where the rinse water goes.
Dry-scrub the whole surface with the wire brush first. Let the tips cut and do not lean. Sweep or vacuum the debris.
Degrease oily spots with a masonry degreaser and scrub. Repeat until misted water sheets evenly instead of beading.
Kill growth with a biocide or dilute bleach. Scrub with tampico or nylon, not wire, then rinse.
Wash down with a heavily charged tampico brush and clean water. Use it as the applicator for any chemical wash.
Rinse until the water runs clear. Wipe a palm across the damp surface and re-wash any slick or chalky spot.
Let the masonry dry for days. Tape a 2 ft square of plastic overnight. Condensation under it means it is still wet.

Test for loose material by dragging a coin or key across it. If it powders or the paint edge flakes, there is a weak layer.
A wire brush that skates over a hard crust needs a scraper first, not more pressure.
Keep carbon wire off aluminum and stainless. It leaves iron that rust-stains.
Rinse the tampico brush clean and hang it by the handle.

Dry brushing masonry throws respirable silica. Wear a NIOSH-approved respirator and goggles.
Paint on masonry from before 1978 may be lead. Test or assume lead and follow EPA lead-safe practice before dry-scrubbing flaking paint.
Do not coat over active efflorescence or damp masonry. Fix the water source first. New concrete needs about 28 days to cure.

Questions about the right tool for your job? Email cs@hydestore.com or call 508-916-6442.