Short answer
Remove weeds and moss from block paving by raking them out of the joints with a weeding knife or joint brush, roots and all, then sweeping the area clean and topping the joints back up with kiln-dried sand. A weedkiller made for paths can help with stubborn growth if used exactly as the label says. Keeping the joints full and the surface swept is what stops them returning.
Why weeds and moss grow in block paving
Weeds rarely push up through block paving from below. Instead, seeds blow in and settle in the top of the joints, where dust, leaf litter and moss build up into a thin layer of soil. As joint sand is lost to rain, weather and cleaning, there is more room for that layer to form.
Moss thrives in shaded, damp spots: along fences and walls, under trees and on north-facing paths. It holds moisture, which makes paving slippery and gives weed seeds an even better place to grow. Tackling both together is far more effective than dealing with one at a time.
Removing weeds by hand
- Wait for a dry day, when the joints are easier to work.
- Use a weeding knife, an old kitchen knife or a purpose-made joint scraper to cut down into each joint and lever the weed out with its roots. A wire joint brush is quicker for moss and small seedlings over larger areas.
- Rake the loosened material out of the joints along with any built-up soil.
- Sweep the whole surface with a stiff broom and bag the debris rather than brushing it onto beds, where the seeds will spread.
- Once the paving is dry, brush kiln-dried sand back into the joints. Our re-sanding guide shows how.
Using weedkiller safely
Weedkiller is not essential, but it can help with deep-rooted weeds that keep returning. If you use one, choose a product labelled for paths and patios, read the whole label and follow it exactly, including the weather it should be applied in and how long to keep children and pets off. Apply it on a still, dry day so it does not drift onto lawns and borders, and never pour leftovers into a drain.
Boiling water, vinegar and salt are often suggested as alternatives. Boiling water can kill small weeds in joints but needs great care to avoid scalds and splashes. Salt and vinegar can harm the plants and soil beside the paving and may affect some surfaces, so they are best avoided where the drive meets a garden.
Moss and green growth on the blocks
Moss and algae on the face of the blocks usually come away with a stiff brush and a paving cleaner suitable for concrete. Pressure washing removes them too, but a jet aimed into the joints blows out sand along with the moss. Our guide on how to clean block paving covers the right technique.
Where moss keeps coming back, look at the cause. Cutting back overhanging branches, clearing leaves regularly and redirecting water from a downpipe or lawn edge all make conditions less welcoming.
Keeping weeds away
Full joints and a clean surface are the best defence. Sweep regularly, especially in autumn when leaves break down into the joints, and pull small seedlings as soon as you see them, before they root deeply. Top up the joint sand whenever it drops below the top of the blocks.
Sealing can help by binding the top of the joint sand so seeds find it harder to settle, but it is not a guarantee. Our guide on whether to seal block paving explains the pros and cons.
When to call a professional
Hand weeding a whole drive is slow, back-breaking work. It may be time to call a professional if the paving is heavily overgrown, the joints are full of soil, or weeds return quickly however often you pull them.
When we clean block paving, weeds and moss are taken out of the joints as part of the job, the joints are re-filled with kiln-dried sand, and a biocide treatment can be added where green growth tends to come back.
Rather have it done for you?
Block paving jet washed, weeds and moss cleared from the joints, with re-sanding discussed on site. Family-run by Jason and Lucas Prior, covering south Essex.
Frequently asked questions
What is the best tool for weeds in block paving?
A weeding knife or joint scraper is best for individual weeds with roots. A wire joint brush is quicker for moss and small seedlings across larger areas.
Does pressure washing remove weeds from block paving?
It removes much of the top growth and moss, but it can leave roots behind and blow sand out of the joints. Rake the weeds out and re-sand the joints afterwards.
Is salt or vinegar safe to use on block paving?
They are best avoided next to gardens, as they can harm nearby plants and soil and may affect some paving. Hand weeding, or a path and patio weedkiller used exactly as labelled, is a safer choice.
Related guides
- How to clean block paving: step-by-step cleaning for block-paved drives and paths, including how to pressure wash without blowing out the joints.
- Re-sanding block paving after cleaning: why the joints need refilling after a clean, why kiln-dried sand is used and how to brush it in so it stays put.
- Should you seal block paving?: an honest look at what a sealer can and cannot do, how to prepare for it and when sealing is better left alone.