Why block paving goes green and weedy
Block paving is full of joints, and joints hold moisture, dust and seeds. In a damp British winter that means algae (the green film), moss in the shaded spots, and weeds rooting into the jointing sand. None of it means the driveway is failing — it just needs a proper clean and fresh sand, not a quick blast.
The safe way to pressure wash block paving
Use a rotary surface cleaner
A flat rotary head cleans evenly at a set height. A bare lance held close cuts stripes into the blocks and strips the face off them.
Keep pressure sensible
Too much pressure pits the surface, blows out jointing sand and can loosen blocks on a weak bed. More pressure is not more clean.
Pre-treat heavy growth
A suitable biocide or detergent treatment loosens algae and black spot so the wash itself can be gentler.
Work with the drainage
Wash downhill towards a drain, and keep silt out of road gullies. The dirty water has to go somewhere.
Why re-sanding is not optional
The kiln-dried sand in the joints is what locks the blocks together and stops them shifting under car wheels. Cleaning always washes some of it out. If the joints are left empty, blocks start to rock, edges spread, and weeds get a free bed to grow in.
Re-sanding is simple but has one rule: the paving must be bone dry first. Brush kiln-dried sand across the surface, work it into the joints with a soft broom, and top up until the joints are full to just below the block surface. Doing it on damp paving just clumps the sand on top.
Keeping weeds and algae away for longer
- • Sweep little and often so dust and seeds do not settle into the joints
- • Treat the first sign of green film rather than waiting for a full coating
- • Pull weeds as soon as they appear, before roots disturb the bedding
- • Consider a sealant after cleaning and re-sanding — it slows staining and weed growth, though it needs reapplying every few years
When it is worth getting a professional in
A domestic pressure washer will freshen up a small patio, but driveways are where DIY goes wrong: striping from a lance, joints washed out and never re-sanded, or oil stains spread across the whole drive. A professional clean with a rotary head, pre-treatment and proper re-sanding usually costs less than putting right a bad DIY job — and the result lasts longer.
Want it done for you?
We clean and re-sand block paving across Mansfield, Sutton-in-Ashfield, Kirkby-in-Ashfield and the surrounding towns. Send a couple of photos for a free, no-obligation price.