How do you remove weeds from block paving? (UK guide)

The short answer

Weeds in block paving grow in the joints, rooting in windblown soil and debris that collects in gaps where the sand has washed out — they rarely grow up from below through a proper membrane and sub-base. Remove them by hand-pulling or scraping the joints with a weeding knife, by a weed killer or natural treatment, or with a weed burner. The lasting fix is prevention: refill the joints fully with kiln-dried sand, sweep regularly to deny weeds the soil they need, and consider sealing to bind the sand. Pressure washing clears weeds but strips the sand, so always re-sand afterwards or the weeds return worse. There is no permanent cure, but full joints and routine care keep them to a minimum.

Weeds in paving are a joint problem, not a base problem. Clearing them is easy; keeping them away is about keeping the joints full.

Weeds in joints

Where they growIn joints, from windblown soil
Manual removalWeeding knife / scraper
Other methodsWeed killer, hot water, burner
Key preventionFull kiln-dried sand joints
OptionalSealing to bind the sand

Why weeds grow in the joints

It is a common misconception that weeds in block paving grow up from underneath. With a correctly built drive — a geotextile membrane over the formation and a compacted sub-base — almost nothing penetrates from below. The weeds you see are growing in the joints between the blocks, rooted in the thin layer of windblown soil, dust and organic debris that collects there over time, especially where the kiln-dried jointing sand has washed or been blasted out. Moss and algae add to the problem in shaded, damp spots. This is why weeds tend to appear along edges, in low spots that hold debris, and on drives that have been aggressively pressure washed. Understanding this points straight to the solution: deny the weeds the soil and the open joints they need.

A joint problem, not a base problem: weeds root in debris in the joints, not below the membrane. Keeping joints full and clean is the real fix.

Ways to remove existing weeds

Several methods clear weeds that have already taken hold, from purely physical to chemical:

Hand-pulling and scraping: a long-handled weeding knife or block-paving scraper dragged along the joints lifts weeds and the debris they root in. Labour-intensive but effective, chemical-free, and it cleans out the joint ready for re-sanding.
Hot water or steam: very hot or boiling water poured on small weeds, or a steam weeder, scalds and kills them without chemicals — good for spot treatment.
Weed burners: a gas or electric thermal weeder wilts and kills weeds with heat. Use carefully and never on or near anything flammable.
Weed killers: a contact or systemic weed treatment kills foliage and, for systemic types, roots. Natural alternatives (acetic acid based or salt-based) exist but can affect surrounding planting and run-off, so apply thoughtfully and follow the label.

For a heavily overgrown drive, a combination works well — treat or burn first to kill, then scrape out the dead growth and debris, then re-sand.

Stopping them coming back

Removal is the easy half; prevention is what stops you doing it again every few weeks. The single most effective measure is to keep the joints full of kiln-dried sand. Empty or half-empty joints are an invitation: they collect debris, hold moisture, and give weed seeds somewhere to root. After any cleaning, weeding or pressure washing, let the paving dry and brush fresh kiln-dried sand into the joints until they are full, settling it down so it stays put. Tightly filled joints leave far less room for soil and seeds to accumulate.

Beyond full joints, routine habits make the biggest difference. Sweep regularly to remove the windblown soil, leaves and grit that weeds root in — a drive that is kept swept simply has less for weeds to grow in. Treat moss and algae with a biocidal cleaner before they build into a layer that holds moisture and seeds. Consider sealing the paving once the joints are full and the surface is clean and dry: a sealer binds the jointing sand so it resists washing out and makes the joints harder for weeds and ants to colonise — it reduces weeds rather than eliminating them, but it lengthens the gap between weeding sessions. Finally, be wary of over-enthusiastic pressure washing, which is self-defeating: it clears the current weeds but strips the very sand that keeps the next lot out, so a hard power-wash is often followed by a worse flush of weeds unless you re-sand immediately. There is no permanent, zero-maintenance cure — paving joints are an outdoor surface and nature will keep trying — but full joints, regular sweeping, prompt treatment and optional sealing keep weeds to an occasional nuisance rather than a recurring battle.

Moss, algae and choosing a treatment

Weeds rarely come alone. On shaded, damp UK paving they are usually accompanied by moss and algae, and the two problems feed each other: a film of moss holds moisture and traps the windblown soil that weed seeds then root in. Tackling moss and algae is therefore part of weed control, not a separate job. A biocidal paving cleaner (a moss and algae treatment) brushed or sprayed on, left to work and then rinsed, kills the growth and slows its return far more effectively and gently than blasting it off — and unlike pressure washing, it does not strip the jointing sand. Treating in autumn or early winter, before growth builds into a thick layer, keeps surfaces clearer and less slippery through the wet months.

For the weeds themselves, the choice of treatment depends on your priorities and surroundings, and there is a sensible option for every preference. Chemical-free options — hand-scraping the joints, a thermal weed burner, or very hot or boiling water — avoid any run-off and suit gardeners who prefer not to use herbicides; they take more effort and may need repeating, but they cause no harm to nearby planting and are well suited to small areas and spot treatment. Weed killers work on larger areas: contact types brown off the foliage quickly, while systemic types travel to the roots for a longer-lasting kill. Natural alternatives such as acetic-acid (vinegar-based) or salt treatments are sometimes used, but they are not automatically gentler on the environment — salt in particular can harm soil and planting and travel in run-off — so they should be applied carefully and kept off borders and drains. Whichever you choose, follow the product label, treat on a dry day so the treatment is not immediately washed off, and remember that the treatment is only half the answer: clearing the dead growth and debris from the joints, then re-sanding them full with kiln-dried sand, is what stops the next flush taking hold. A drive that is kept swept, its joints kept full, and its moss kept down simply gives weeds far less to work with, which is why prevention beats repeated removal every time.

Frequently asked questions

Do weeds grow up through block paving from below?

Rarely, if the paving was built correctly with a geotextile membrane and compacted sub-base. The weeds you see almost always grow in the joints, rooted in windblown soil and debris that collects where the jointing sand has thinned.

What is the best way to stop weeds in block paving?

Keep the joints fully filled with kiln-dried sand, sweep regularly to remove the soil and debris weeds root in, treat moss early, and consider sealing to bind the sand. Full, clean joints are the key to fewer weeds.

Does pressure washing get rid of weeds for good?

No. It clears existing weeds but blasts out the jointing sand, leaving open joints that weeds quickly recolonise. If you pressure wash, you must re-sand the joints afterwards or the weeds return worse than before.

Sources & further reading

Figures on this page are typical UK ranges drawn from published sources and depend on your specific site. They are guidance, not a quotation.