How to Remove Efflorescence from Masonry
The white salty bloom on British brick and render is efflorescence - cosmetic, but always a signal that water is moving through the wall. Removing it is simple; finding and fixing the water source is the important part. Skip the fix and the bloom returns within weeks.
Identify the moisture source first
Walk the elevation on a dry day and look above the bloom for cracked hoppers, leaking gutters, broken pointing, or a bridged damp-proof course (DPC). Efflorescence directly below a hopper usually means a gutter defect; along the DPC line it means raised external ground levels or render bridging.
Brush off dry salts - never wash wet
Use a dry, stiff-bristle (non-wire) brush to sweep the salts away. Washing at this stage drives soluble salts back into the masonry and makes the bloom worse when the wall dries out. Catch debris on a dust sheet for disposal - some efflorescence contains sulphates.
Treat residual staining with a masonry cleaner
Once brushed, apply a diluted masonry cleaner such as HG Brick & Patio Cleaner or a 5% hydrochloric acid solution (on brick only, not render). Wet the wall with clean water first to prevent deep penetration of the cleaner, scrub with a soft brush, and rinse thoroughly. Wear goggles and acid-rated gloves.
Fix the water source
Repoint defective mortar joints with a lime-based mortar matching the original mix. Re-secure or replace leaking hoppers and downpipes. Lower external ground levels so the DPC sits 150mm above finished ground. On rising damp, commission an RICS-qualified damp survey before any chemical DPC injection.
Allow to fully dry before redecoration
The wall must dry for a full British summer (typically 8-12 weeks of progressive drying) before any paint goes on. Test with a protimeter - under 75% WME is the threshold for breathable silicone masonry paint. Painting too soon traps moisture and brings the bloom straight through the new finish.
Put it into practice!
Use our simulator to apply these tips directly on your project photos.