Driveway guide
Sealing block paving: when it is worth it and when to leave it
Sealing block paving is one of the jobs I get asked about most once a drive has been cleaned, and my answer is not always yes. A good sealer, put on at the right time over clean, dry, fully sanded joints, keeps a drive looking newer for longer and slows weeds down. Put on over damp blocks, fresh efflorescence or half-empty joints, it seals the problem in. This guide covers when it pays, and when it does not. If the drive needs cleaning first, start with the block paving cleaning guide.
What sealing block paving actually does
A block paving sealer is a liquid coating rolled or sprayed over the surface. It soaks into the top of the blocks and, more usefully, binds the top of the kiln-dried sand in the joints so rain, brushes and pressure washers do not pull it out. Full joints are what keep block paving interlocked and what leave no room for windblown seeds, which is why the weeds guide puts the joint sand ahead of any chemical.
It also makes oil and food spills easier to lift before they soak in, and most products deepen the colour slightly. What it does not do is fix anything. A sealer will not level a dip, stop blocks rocking or cure a drainage fault.
Which block paving sealer to choose
- Acrylic sealers
The common, cheaper option. They give a matt, satin or gloss finish and are easy to recoat, but they wear faster on a busy drive.
- Polyurethane sealers
Tougher and better at holding joint sand under tyres, usually at a higher price. A sensible choice where cars turn on the blocks every day.
- Penetrating or impregnating sealers
Soak in and leave little or no visible film. They change the look least and suit people who just want stain resistance.
On finish, a lot of homeowners regret gloss once it is down. It can look like wet concrete in bright sun and shows wear at the turning points first. A matt or satin finish is the safer choice on a driveway. Whatever you buy, check the manufacturer says it is suitable for vehicle areas and for the type of block you have.
When to seal, and when to wait
The paving makers give similar guidance on timing. Bradstone, for example, says to seal in dry weather between about 10°C and 25°C, to wait 12 to 24 hours after re-sanding before sealing, and to keep off the surface until it is dry, typically three to four hours. In practice that means a run of dry days in late spring or early autumn, not a damp October weekend.
New concrete blocks are the other reason to wait. Many show a white bloom called efflorescence in their first months, as salts work out of the concrete. It weathers off on its own, but a sealer put on over it can trap it under a cloudy film. Most installers let a new drive go through a season before sealing it.
The milky finish problem. A sealer that turns white or patchy has almost always gone on over damp blocks, or rain arrived before it cured. Joints hold moisture for longer than the face of the block, so a drive that looks dry at lunchtime after a wet morning usually is not.
How sealing block paving is done properly
- Clean it. Remove weeds, moss, oil and dirt, usually with a pressure washer and a rotary cleaning head. See the driveway cleaning page for what that involves.
- Let it dry. Fully, joints included. On clay ground in a wet spell this can take longer than people expect.
- Re-sand the joints. Brush kiln-dried sand in until the joints are full to the top, then brush off the surplus.
- Seal. Apply in the coats the manufacturer specifies, with no puddling in low spots.
- Keep off. Foot traffic and cars stay off for the time the product states.
How often to reseal
Bradstone suggests resealing every three to five years depending on use and exposure. Turning areas and the strip under where a car is parked wear first, so a drive often looks tired in patches before the whole surface needs doing. Resealing over an old coat usually needs a clean and a check that the old sealer is still bonded.
When sealing is not worth it
- The drive is dipping or rocking. Fix the base first. Sealing a failing drive just adds cost to a job that needs lifting and relaying, as the driveway repair guide explains.
- It is permeable paving. Permeable blocks rely on open joints filled with grit to drain. Check with the block maker before putting anything on them, because blocking the joints can stop the drive doing the job that keeps it within the drainage rules.
- You expect repairs. A sealed area is harder to lift and relay invisibly. If a service trench or a dropped section is likely soon, do that first.
- You will not reseal. A worn, patchy sealer can look worse than no sealer. If you would rather not repeat the job every few years, keeping the joints topped up with sand gets you much of the benefit.
Doing it yourself or getting it done
Sealing is a reasonable DIY job on a small, flat drive in good weather. The parts people get wrong are the drying time and the re-sanding, not the rolling. On a larger drive, or one that needs a deep clean first, it is usually done as one visit with the clean. If you are in MK and the drive needs both, my team and I can price it under driveway cleaning in Milton Keynes, and if it turns out the drive is past saving, the Milton Keynes driveways page covers replacement.
Written and reviewed by the PaveLocal team. We build and specify driveways across Northamptonshire, Buckinghamshire and Bedfordshire. Pricing and specification guidance on this page reflects what these jobs cost and involve in this region, not a national average.