Final Spreading with Joint Brushing

Spreading comes only after the blocks are laid, the edgings are set and the cut pieces along the edges are in place. The surface must be dry and swept clear of cutting debris. The method is simple, but it only works if each step is done thoroughly.

• Spreading the sand: dry sand is scattered over the surface in a thin, even layer.
• Brushing: the broom moves in changing directions, ideally diagonally across the joints, so the sand drops into the gaps instead of sitting on top.
• Compacting: a plate compactor with a protective rubber or polyurethane mat goes over the surface several times. The blocks settle into their bedding layer and the sand packs down in the joints.
• Topping up: after compacting, the sand in the joints drops, so more is added and brushed in again. This cycle repeats until the joints are full right up to the edge of the blocks.
• Cleaning off: the surplus sand is swept away. Sometimes a thin layer stays on the surface for a few days so that foot traffic and rain can work it further into the joints, and the rest is removed afterwards.

Why is one sweep not enough? In a narrow joint, sand first catches only near the top. Compacting and repeated topping up get it down to the full depth, and only a full joint really holds the blocks in place.

The right material depends on how wide the joints are, how much load the surface carries and how much maintenance you are willing to do.

Kiln-dried sand

This is the usual choice for paths, patios and yards. It is dry, fine, clean sand, usually with a grain size of roughly 0 to 2 mm, so it runs easily into narrow joints. The downside is that rain and sweeping gradually wash some of it out, so you need to top it up now and then.

Polymeric jointing sand

This is sand mixed with a binder that hardens after you wet it with a fine spray. It washes out less and makes it harder for weeds to grow. It suits driveways and areas with heavy use. It is less forgiving, though. The surface must be completely clean before you wet it, otherwise the blocks will end up with a haze or smears. It also must not rain before the binder has set. The manufacturer states the minimum joint width and depth and the curing time, so stick to them.

Fine stone grit

Paving with wider joints, and permeable paving that is meant to let water drain through, usually gets fine crushed stone in the joints, as recommended by the paving manufacturer. Ordinary sand would quickly wash out of joints like these.

The effort varies a lot from one surface to another, and that affects how long the job takes and what it costs.

• A large, flat area with a simple shape goes quickly, and the plate compactor turns easily on it.
• Irregular areas with curves, steps, edgings, manhole covers and gullies need finishing by hand.
• Narrow joints fill more slowly and need more rounds of brushing.
• Textured or brushed block surfaces hold sand in small hollows, so cleaning off takes longer.
• Polymeric sand needs more care than ordinary sand: cleaning, wetting and keeping an eye on the weather.
• Re-sanding old paving is usually more work than a new surface, because weeds, moss and soil have to be scraped out of the joints first.

In practice it often happens that a surface looks finished, but after the first winter the blocks start to rock. The cause is almost always in the joints.

• Working in the wet: damp sand clumps together, stays on top and never gets down into the joint.
• Joints filled only at the surface: after the first rain the sand drops and the blocks lose their support.
• Skipping compaction: without it, the blocks do not settle and the sand does not pack down.
• Compacting without a protective mat: a bare steel plate scratches or chips the edges of the blocks.
• Compacting a wet or dirty surface: the dirt gets pressed into the blocks and leaves stains.
• The wrong material: clayey, dusty or coarse sand does not fill the joints properly and can stain light-coloured paving.
• A strong jet of water: pressure washing right after sanding flushes the sand straight back out of the joints.

You can handle both the first sanding and later topping up yourself. You can hire a plate compactor from a tool hire shop. Ask for one with a paving mat fitted. If the paving belongs to a block of flats, agree it with the building management or owners' association first.

1. Wait for dry weather and check that both the paving and the sand are dry.
2. Sweep the surface and remove cutting debris, leaves and soil.
3. When re-sanding old paving, scrape weeds and dirt out of the joints.
4. Spread the sand in a thin layer, working in smaller sections.
5. Brush in changing directions until the sand starts to stay on the surface.
6. Run the plate compactor with its protective mat over the area, working from the edges towards the middle in overlapping passes.
7. Top up the sand, brush it in again and repeat the compacting if needed.
8. Sweep off the surplus, or leave a thin layer on the surface for a few days and then remove it.
9. With polymeric sand, follow the manufacturer's instructions: clean the surface thoroughly and only then wet it gently.

Whether you are signing off a contractor's work or checking your own, walk over the surface carefully, ideally in daylight.

• Joints are full up to the edge of the blocks, with no visible gaps
• No block rocks or clicks when you walk over it
• The surface is even, with no sunken spots around edgings and manhole covers
• Block edges are not scratched or chipped from compacting
• There are no dirt stains or polymeric sand smears on the paving
• Surplus sand has been removed, or it is agreed when it will be swept off
• You know which jointing material was used, so you can top up with the same later