Why joints fill with growth
Block paving is laid on sand with narrow sand-filled gaps between each block. Over time those gaps collect dust, leaf litter, tyre grit and wind-blown soil. That mix holds moisture and gives seeds and spores a place to settle. The blocks themselves stay fairly clean on a busy drive, but the joints slowly turn into a thin strip of growing medium running in every direction.
Moss on shaded drives and paths
Moss is most common where paving rarely dries out: along a north-facing wall, under trees, beside a fence or on a path that sees little foot traffic. It creeps from the joints across the face of the blocks and can make the surface slippery in winter. Shaded patios suffer the same way, which is often why one corner of a garden turns green while the rest stays clear.
Weeds in sand-filled joints
Weeds root into the joint material and use it as soil. Small seedlings are easy to pull, but established weeds leave roots behind, and pulling them often takes joint sand with them. That opens the gap further, giving the next seeds even more room. Left long enough, roots can also disturb the edge of blocks.
Pulling, scraping and spraying: what each does
Each common approach deals with part of the problem. None deals with all of it on its own.
- Pulling removes the visible weed but often leaves roots and lifts joint sand
- Scraping clears surface growth from the joints but leaves spores behind
- Spraying a weedkiller on its own kills growth but leaves dead material and dirt in place
- Cleaning lifts dirt and growth but does not stop spores already in the joints
Cleaning then treating: the order that works
OOR External identifies the paving, its condition and the joints before choosing the pressure and technique. Block paving faces can take controlled pressure, but joints need care, because washing removes contaminated sand along with moss and weeds. Once the surface is clean, a biocide treatment is applied to kill the spores and growth left deep in the joints and porous surfaces, which slows the return of green and black growth.
Doing it in that order matters. Treating first leaves dead growth stuck in dirty joints, while cleaning without treating gives the remaining spores a fresh, open surface to recolonise. The service page sets out how a driveway visit runs, and the separate driveway guide covers block paving and concrete in more detail.
Slowing regrowth
Growth will return eventually, because seeds and spores arrive on the wind and on shoes and tyres. You can slow it by sweeping regularly so debris does not build up in the joints, keeping overhanging shrubs trimmed so the surface dries, and dealing with the first small weeds before they establish. A treated surface gives you a much better starting point than an untreated one.
When a professional clean helps
A professional clean is worthwhile when growth has spread across most of the drive, when the paving is slippery, or when you want the whole surface done evenly rather than in patches. Send a few photographs of the drive or patio and Jordan will recommend an approach and provide a free written quotation.