Pressure Washing Brick: What You Need to Know

Brick is a resilient material but it requires a considered approach to pressure washing. Modern hard bricks can tolerate moderate pressure with good results. Older, softer handmade bricks, particularly on Victorian and Edwardian properties, need lower pressure to avoid surface erosion and damage. The mortar joints are often the most vulnerable element — old lime mortar can be eroded by excessive pressure.

The type and condition of mortar determines the maximum pressure you can safely use on a brick wall. Modern sand-cement mortar is relatively hard and resilient. Old lime mortar is softer and more permeable but also more flexible. Using excessive pressure on lime-mortared walls can erode the mortar from joints, which is expensive to repair and reduces the weather-tightness of the wall.

Efflorescence — the white crystalline deposits that sometimes appear on brick surfaces — requires a different approach to biological growth. It's caused by soluble salts moving to the surface as water evaporates from the wall. Pressure washing alone won't remove it permanently; the source of water driving the salts to the surface needs to be identified and addressed.