Moss and Growth Between Pavers

Moss and weeds are not the same growth, and need different treatment

Moss is a simple, rootless plant that spreads by spores and only needs a consistently damp surface film to establish, which is why it can grow directly in joint sand with almost no soil at all. Weeds are ordinary vascular plants with real roots, and they need enough accumulated organic debris in the joint to actually count as soil before a seed can germinate there. That difference matters for treatment: a moss killer applied to the surface handles moss because there is no root system to leave behind, but a weed pulled or burned off at the surface regrows from the root left in the joint unless the accumulated debris is cleared out with it.

Why it grows in the joints in the first place

Joint sand holds moisture, and shaded hardscape stays damp for long periods after rain or irrigation. Add organic debris breaking down into the joint over a season or two and you have soil, moisture and shade in one place, which is everything moss and weeds both need, just in different amounts. North-facing and tree-shaded patios always go first.

What pressure does to joints

A pressure washer aimed into a paver joint blasts out the jointing sand that holds the whole installation in place. Once the sand is gone the pavers shift under foot traffic, the surface becomes uneven, and water penetrates straight to the base material where it undermines the bedding layer. The patio looks clean the day it is done and is structurally worse than before.

When it's no longer a cleaning job

If pavers have already shifted, rocked, or settled unevenly before anyone touches them, that is base movement, not a growth or sand problem, and cleaning plus re-sanding will not correct pavers that are no longer level. That needs the affected pavers lifted and reset on corrected bedding, which is a hardscape repair rather than a cleaning service. Cleaning a patio that is already structurally uneven just makes the unevenness easier to see.

The right sequence, and reducing recurrence

Growth is treated and removed, the surface is cleaned at appropriate pressure, and then joints are re-sanded if sand was lost in the process. Skipping the re-sanding step is what turns a cleaning into a repair job a year later. Beyond that, improving drainage, cutting back overhanging growth to let sun reach the surface, and keeping organic debris off the hardscape all reduce how fast it returns. Polymeric jointing sand resists growth better than plain sand where re-sanding is happening anyway.