If the sand keeps disappearing out of your paving joints every winter, the sand is almost never the real problem. Jointing sand washes out because water is moving across or under the paving faster than it should — and until you deal with the water, you can re-sand every year for the rest of your life.
This is one of the most common complaints we hear after a run of Cape Town winter storms: bricks starting to rock, weeds coming through, dark gaps between every paver, and a fan of grey sand washed across the pavement outside the gate. Here is what is actually happening and what fixes it properly.
Why the sand leaves in the first place
Jointing sand does a real structural job. It is what makes interlocking paving interlock. Sand-filled joints transfer load from one paver to its neighbours, so a car tyre is carried by dozens of bricks rather than the one it is sitting on. Empty joints mean each paver works alone, which is when rocking, lipping and cracking start.
Sand goes missing for a handful of reasons, usually more than one at a time:
- Sheet water running across the surface. Where a driveway has no cross-fall to a drain, winter rain runs the length of the paving and scours the joints as it goes. The washout is always worst along the natural flow line.
- Pressure washing. A 15 MPa lance held close to a joint strips it in seconds. Most driveways we see with badly empty joints were pressure washed at some point without being re-sanded afterwards.
- The wrong sand. Soft, rounded river sand and Cape Flats builder’s sand do not lock together. They flow. Coarse, angular, washed crusher sand does.
- Joints that are too wide. Hand-cut edges, mixed brick batches or sloppy laying leave gaps a jointing sand simply cannot bridge.
- No edge restraint. If the perimeter course is not held by a concrete haunch or kerb, the whole field creeps, joints open and sand pours out sideways.
- Water coming from below. On Durbanville clay, water that cannot drain through the base rises and pushes fines up and out of the joints. That one is rarer, but it is the nastiest.
River sand versus polymeric sand
There are broadly three things people put in paving joints. They behave very differently.
| Material | How it behaves | Best used for |
|---|---|---|
| Soft river / builder’s sand | Rounded grains, flows easily, washes out fastest, feeds weed seed | Honestly — nothing. Avoid it in joints. |
| Washed crusher sand (angular) | Sharp grains that wedge together and stay put; cheap and easy to top up | Most driveways, patios and pathways |
| Polymeric sand | Graded sand with a binder that sets hard when wetted; resists washout and weeds | Steep falls, storm-scoured areas, pool surrounds, joints under 10mm |
Polymeric sand is the product people ask about by name, and it does work — but it is fussy. It must go into bone-dry joints, be swept in fully, compacted, the surface blown completely clean, then activated with a specific light watering sequence. Rush any of those steps in Cape Town’s damp winter mornings and you get a hazy residue stuck to the paver faces that is genuinely difficult to remove. It also needs the joint to be filled to a proper depth; a 5mm skim over an empty joint will crack and lift out in sheets.
It is also not a structural repair. Polymeric sand on paving with a failing base just means your failure will be tidier.
Fix the water first
Every genuinely permanent fix we do for washout starts with drainage, not sand:
- Give the water somewhere to go. A channel drain across the garage line, or at the low point of a driveway, stops sheet flow dead. Costs run R1 200 – R2 800 per running metre installed including connection to stormwater, so a typical 3–4m single-garage channel lands at roughly R3 600 – R11 200 fitted.
- Check the falls. Paving needs a consistent slope. Where it is flat or falls the wrong way, sand loss and ponding follow.
- Intercept water coming off the roof and the slope above. On Plattekloof and Hout Bay properties, most driveway scour is water arriving from higher up the erf, not rain landing on the driveway itself.
- Restore the edge restraint. Re-haunch loose perimeter courses before re-sanding, or the sand will just keep leaving through the gap.
Our full breakdown of options, including soakaways at R8 000 – R25 000, is in the driveway drainage guide.
How to re-sand paving properly
- Clear the joints. Remove weeds, moss and old contaminated sand from the top of the joint. A joint half-full of organic muck will not accept new sand.
- Let everything dry completely. This is the step people skip. Damp joints will not draw sand down.
- Sweep sand in, in stages. Spread, sweep diagonally across the joints, then repeat. Do not try to fill in one pass.
- Vibrate it down. A plate compactor with a rubber mat settles the sand into the full depth of the joint and reveals where more is needed. On a small patio, a rubber mallet and patience will do.
- Top up and repeat. Expect two or three rounds before the joints stop swallowing sand.
- Blow the surface clean before any wetting, especially with polymeric products.
Do this in late spring or summer. Attempting a re-sand in June in Cape Town is wasted effort — more detail on timing and yearly care is in our paving maintenance guide, where a full professional service (clean, re-sand, moss treatment, inspection) runs R2 500 – R5 500 and the DIY equivalent R600 – R1 200.
When re-sanding is not enough
Re-sanding buys you nothing if the base has gone. The tell-tale signs are pavers that rock underfoot, a dip or trough that holds water, joints that reopen within weeks of being filled, and bricks whose edges have started chipping against each other. At that point the correct repair is a lift and relay of the affected section: bricks come up, the base is corrected and recompacted, and the same pavers go back down. Localised lift-and-relay work sits around R380 – R650 per m² — typically 40–60% of a full replacement — as covered in our piece on driveway cracking causes and fixes.
Left alone it does not stabilise. Each winter the open joints let more water into the base, the base softens, more bricks move, and a small patch becomes a much bigger one. If you would rather have someone look at it before that happens, our our paving repair service can tell you whether it is a sand job or a base job, and you can get hold of us here.
Quick answers
Why does my paving sand keep washing out?
Almost always because water is running across the surface instead of into a drain, often combined with soft river sand in the joints, pressure washing without re-sanding, or a loose edge restraint. Fix the water and the sand stays.
Is polymeric sand worth it in Cape Town?
On steep falls, storm-scoured driveways and pool surrounds, yes. It must go into completely dry joints and be activated correctly, which is why it is best applied in summer rather than during the winter rainfall months.
How often should paving be re-sanded?
A well-drained driveway with angular crusher sand typically needs topping up every couple of years, and always after pressure washing. If yours empties every single winter, the problem is drainage or the base, not the sand.