Weeds are telling you the joints are empty.

Where they actually come from

Under a properly built paver surface there is bedding sand, then compacted granular, then geotextile, then subgrade. Nothing is germinating through that.

What happens instead: joint sand washes out over a few seasons, the empty joint collects dust, organic debris and windblown soil, and that becomes a thin growing medium sitting at the surface.

Which is why weeds appear years after installation rather than immediately, and why they appear in some joints and not others — the ones that lost sand first.

What actually stops them

Re-jointing with polymeric sand. The joint gets cleared out to at least 25 mm, refilled, compacted in and watered to activate the binder. A full, set joint has no room for debris to collect and no space for a root.

That is the fix. Everything else is managing symptoms.

What makes it worse

Pressure washing on a narrow jet. The fastest way to strip polymeric sand out of joints. If you pressure wash, use a wide fan at low pressure and expect to top up the sand afterwards.

Pulling weeds aggressively. Tearing them out takes the remaining joint material with them and enlarges the gap.

Leaving debris on the surface. Leaves and organic matter left over winter break down into exactly the growing medium the seeds need.

Salt-based weed killers. They work on the plant and do nothing about the empty joint, so it recurs, and repeated salt is hard on the pavers.

The maintenance rhythm

Sweep the surface a few times a year, particularly in autumn. Check joint level annually and top up before it drops far. Re-joint properly every five to ten years.

Done on that rhythm, weeds are a non-issue. Left for fifteen years, the joints are empty, the pavers have started to move, and re-jointing alone will not fix it.