Why using the wrong mortar is destroying your brick steps
In short: Most homeowners think a crack in their masonry just needs a quick patch. In reality, using high-strength structural materials on soft bricks can actually accelerate decay. To fix it properly, you have to undo previous repairs and understand the delicate physics of expansion and contraction.
The primary culprit behind many failing brick steps is 'over-engineering.' When homeowners or contractors use Type S mortar—a heavy-duty, structural material—on standard bricks, they create a mismatch in flexibility. Because Type S is much harder than the surrounding masonry, it doesn't allow for natural movement. As temperatures shift, the bricks expand and contract; if the mortar is too rigid to move with them, it creates internal stress that results in hairline cracks.
The solution lies in using Type N mortar. This specific mixture provides the necessary strength while remaining flexible enough to accommodate freeze-thaw cycles. To properly repoint, a mason must first remove old material by cutting out joints to a depth of 3/4 inch using a masonry grinder with a vacuum attachment to manage dust. A strategic order is required: horizontal lines are addressed first, followed by vertical ones, which creates a pocket that allows the blade to stop safely before hitting the brick.
The application process mimics icing a cake, utilizing a grout bag to squeeze mortar into the joints. The consistency must be slightly wetter than normal to ensure smooth flow, though water should be added incrementally. Once squeezed in, a flat jointer is used to press and slick the surface. This creates a weather-proof seal that eliminates the need for external water sealants—which can actually create dangerous slipping hazards by trapping moisture on the surface.
Opens the Intellect+ feed with this card first. Swipe up for the next one.
Sources
- Summary by Intellect · source: How to Repoint Brick Steps | Ask This Old House
To cite this card, link to https://intellectplus.co.uk/app/society-how-to-repoint-brick-steps-ask-this-old-house.
How we source, check and correct cards: Editorial standards.
General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.
Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?
Related
More in Home & housekeeping · More in Society · Latest · A–Z · All topics
