Why are weeds growing through my driveway?

Almost everyone assumes weeds are coming up through the drive from the soil below, and almost nobody is right. A properly built drive has a membrane and 150mm or more of compacted stone under it; nothing is pushing through that. What happens is that seeds land in the joints, where a small amount of windblown silt and decayed leaf matter has accumulated, and germinate in that.

Which means the fix is about the joints. On block paving, full joints of kiln-dried sand, compacted by vibrating rather than just brushed in, leave a seed almost nothing to root into. A stabilising sealer over properly re-sanded joints goes further and also stops ants excavating them. Empty joints are the real problem — and they matter far more than the weeds do, because empty joints mean the pavement has lost its interlock.

Getting rid of what is there wants treating rather than pulling or blasting. Weeds cut or pressure-washed off at the surface regrow from the root within weeks. A systemic treatment that reaches the root, or removal with the root intact, is what actually clears them. Moss and algae are a different organism and want a proper paving biocide, left to work before anything is washed off.

Where the growth keeps returning quickly, the cause is usually damp rather than seeds. A shaded, north-facing drive, an area that ponds, or a spot receiving run-off from a bank or a lawn stays wet, and wet surfaces grow things. Treating the growth is the easy half; correcting the fall, clearing a channel, or stopping soil washing onto the drive is what ends it.

Two things not to use. Salt attacks mortar and concrete and corrodes any reinforcement it reaches. Bleach and strong household chemicals stain some stone, damage jointing and kill whatever they run off into — which, on a drive that drains to a watercourse, matters. Proper paving biocides are inexpensive, work better and do not wreck the surface.