How do I get rid of weeds growing in paving and gravel?

Why weeds appear in joints that look solid, the physical and chemical options, and the jointing repair that actually stops them coming back.

Difficulty: beginner
Time: 1 hr
Read: 3 min
Safety: caution

Short answer

Scrape or burn off the top growth, then deal with the cause: weeds grow in the debris that collects in joints, not in the paving. Clean out and refill the joints to full depth and the problem largely disappears.

Weeds in paving are not growing out of the ground beneath. They are germinating in the film of dust, moss and organic debris that fills the top of every joint. That is why a patio can be laid on a membrane and still grow weeds — and why cleaning is a more permanent solution than spraying.

Safety

Never use weedkiller where it can run off into a drain, a pond or a watercourse — most drives and paths drain to a surface water drain that discharges to a river. Boiling water burns badly and spits off hard surfaces; carry it in a lidded container and pour at ankle height. Read the label on any product and observe the pet and wildlife exclusion times.

Step by step

Clear the top growth first.A block paving brush or a joint scraper pulls established weeds out with their roots. A weed burner is quicker on a large area and kills seedlings without chemicals.
Rake the joints out properly.This is the actual fix. Scrape each joint down to sound jointing material, removing the compost layer at the top where the seeds germinate.
Sweep and wash the whole surface.Clear the debris entirely rather than sweeping it into the next joint. A stiff brush and a hose; a pressure washer only if the jointing can take it.
Refill the joints to full depth.Kiln-dried sand for block paving, mortar or a resin jointing compound for slab paving. A joint filled to the top has nowhere for a seed to sit.
Deal with gravel differently.Rake the gravel to disturb seedlings, and remove leaf litter each autumn. Gravel weeds grow in the accumulated organic matter on top, not in the stone.
Use weedkiller carefully if you use it at all.A targeted spot treatment on established perennial weeds, applied in dry still weather, well away from drains and planting. Never a blanket spray on a surface that drains to a watercourse.
Consider the natural options honestly.Boiling water and vinegar-based products kill top growth and are fine for seedlings in joints. Neither touches an established perennial root, so they need repeating.
Set up a routine.A brush over in spring and autumn and a leaf clear in November prevents almost all of it. Weeds in paving are a housekeeping problem more than a gardening one.

Tips

A long-handled joint scraper saves your back and does a better job than a screwdriver on hands and knees.
Do the job before the weeds seed. Ten minutes in May saves an hour in August.
Resin jointing compounds resist weeds far better than sand or weak mortar, and are worth considering when a patio needs rejointing anyway.

Common mistakes

Pressure washing weeds out of the joints — It removes the jointing material along with the weeds, leaving a deeper, dirtier joint that weeds colonise faster. If you pressure wash, plan to rejoint afterwards.
Spraying weedkiller on a drive that drains to a road gully — It goes straight into the surface water system and out to a watercourse. Several products are specifically restricted from use on hard surfaces for this reason.

If it doesn't work

Weeds back within weeks of clearing

Cause: Joints not refilled, so the seed bed is still there — Fix: Rake out and refill the joints to full depth. Clearing without rejointing is a treadmill.

Moss rather than weeds in the joints

Cause: Damp, shaded, poorly drained paving — Fix: Improve drainage and light where possible, clean off the moss, and treat with a proprietary moss killer suitable for hard surfaces.

Deep-rooted weed regrowing from the same spot

Cause: Perennial root under the paving — Fix: A targeted systemic treatment on the growing leaves is the only thing that reaches the root. Lifting the slab is the alternative.

Weeds all over a gravel area with a membrane

Cause: Germinating in debris on top of the gravel — Fix: Rake, clear leaf litter, and top up gravel. The membrane is doing its job — the seeds are arriving from above.

Questions people ask

Does a weed membrane stop weeds in gravel?

It stops them growing up from the soil below. It does nothing about seeds landing in the dust and leaf litter that accumulates on top, which is where most gravel weeds actually grow.

Is boiling water an effective weedkiller for paths?

For seedlings and annuals in joints, yes — and it is free and leaves no residue. It does not kill established perennial roots, which will regrow, so it needs repeating.