How to clean and reseal block paving without wrecking it
By Terry O'Reilly, owner, 17 years on the tools. Updated . 4 min read.
Clean block paving with a fan nozzle at a low angle across the joints, never a pencil jet down them, let it dry for a couple of days, brush fine dry sand into every joint, then roll on a sealer made for block paving. A light wash and top-up of sand once a year is a DIY job; a full clean, re-sand and reseal every three to five years is worth having done properly.
Why does block paving go green and weedy?
Block paving has joints, and joints hold sand. Over a few years rain washes some of the sand out, wind blows dust and seeds in, and you get moss in the shade, weeds in the sun and a black or green film over the lot. None of that is the blocks failing. It is the joints filling with the wrong thing.
A clean and reseal puts it back: the joints are cleared, refilled with fine dry sand and locked in with a sealer, so there is nowhere for a seed to root and the surface sheds dirt instead of holding it. It is the difference between a drive that looks ten years old and one that looks new. That is what we do on our cleaning and sealing jobs.
Can I jet wash block paving myself?
You can, and most of the damage I get called to fix was done with a pressure washer bought on a bank holiday. The four mistakes, in order:
- Pointing the lance straight down the joints. It blasts the sand out to the bottom, the blocks lose their support and start to rock. Work at a low angle across the joints, not along them.
- Using a pencil jet up close. It etches the face of the block and leaves pale stripes you can never get out. Use a fan nozzle at least 30cm from the surface.
- Not re-sanding afterwards. Washing always takes some sand out. If it is not replaced, the joints fill with dirt again within a year and the blocks move under the car.
- Sealing a damp drive. Sealer on blocks that are not bone dry goes cloudy and peels. It needs a couple of dry days after the wash.
A light wash once a year with a fan nozzle, then a brush of fine dry sand into the joints, is fine to do yourself and keeps a sealed drive looking good.
What does a professional clean and reseal involve?
- Treat. A moss and algae treatment goes on first so the wash lifts it rather than smearing it.
- Wash. A rotary surface cleaner, which washes evenly without stripes and without gouging the joints, then a lance for the edges and the awkward bits.
- Dry. The drive dries fully, usually a day or two depending on the weather.
- Re-sand. Kiln-dried sand brushed into every joint and compacted down.
- Seal. A sealer rolled or sprayed on, which locks the sand in the joints, stops weeds rooting and makes oil and dirt wash off.
Two days on site for most drives, and you keep off it until the sealer has cured. Terry tells you when that is, as it depends on the sealer and the weather.
Would you rather just ask Terry?
A photo and a question on WhatsApp gets a straight answer, usually the same day.
Which sealer should I use on block paving?
There are two main kinds. Acrylic sealers are cheaper, go on easily, and give a wet-look or a satin finish; they need redoing more often. Polyurethane sealers cost more, last longer and stand up better to tyres and oil. Both come in matt and gloss. On a brindle or a buff block a matt finish looks natural; on charcoal a satin finish brings the colour back.
Whatever you use, the drive must be clean, dry and re-sanded first, and it must be a sealer made for block paving, not a patio or decking product. The wrong one turns white in the first wet week.
How often should block paving be cleaned and resealed?
| Job | How often | DIY or professional? |
|---|---|---|
| Sweep and pull the odd weed | As you go | You |
| Light wash and top up the sand | Once a year | You, with a fan nozzle |
| Full clean, re-sand and reseal | Every 3 to 5 years | Us, or a careful DIY over a dry weekend |
| First seal after laying | Once the blocks have weathered, a few weeks in | Us, as part of the job if you want it |
A sealed drive needs a lot less of all of it. Dirt sits on the sealer rather than in the block, so a hose and a brush do most of the work.
When is cleaning not enough?
If blocks are rocking, if there are dips where the wheels go, or if the edges have spread away from the lawn, the problem is under the drive, not on it. Cleaning and sealing a sunken drive is money down the drain; the base needs sorting first. Why block paving driveways sink explains how to tell, and a relay puts the same blocks back on a proper base, after which a clean and seal makes them look new.
We clean and seal drives and patios across Milton Keynes, from the semis in Bletchley to the older houses in Stony Stratford and out to Newport Pagnell. Indian sandstone patios get the same treatment. A photo of the drive on WhatsApp gets you a rough idea of the price the same day, and what people say about the finish is on the reviews page.
