Why is my paving sinking?

When someone calls us about a driveway that has "suddenly" sunk, it has not. A segmental pavement is a system: compacted base, bedding sand, pavers locked together by their joints, held in by restrained edges. When one part starts to go, the others compensate for a while, and the pavement looks fine while it quietly deteriorates underneath. By the time there is a visible dish, the failure has been running for 18 months to three years. The good news is that if you catch it at the right stage, the fix is a few hundred dollars instead of a few thousand.

Stage one: the joints are emptying.

This is the first thing to go and the cheapest thing to fix, so it is worth walking out and looking today. If you can see down between the pavers, the joint sand is leaving. In Geraldton that usually means loose washed sand was used and the Doctor, our strong afternoon south-westerly, has been scouring it out every summer afternoon since the job was done. Coastal rain takes the rest.

Empty joints matter far more than they look. The whole structural idea of segmental paving is interlock: each paver is braced by its neighbours through a full, firm joint. Empty the joints and every paver becomes an individual little block sitting on sand, free to rock and to work the bedding out from under itself. Fixing it at this stage is a re-sand at $15 to $35 per square metre with a stabilised jointing sand that the wind cannot take. That is the single best-value maintenance job in paving. There is more on it in the maintenance guide.

Stage two: weeds, then rocking.

Weeds in the joints are not a weed problem. They are a symptom, and the symptom is the empty joint from stage one. Spraying them treats the leaf and ignores the cause, and they will be back next winter after our 440mm of rain arrives.

Rocking is the next rung and it is more serious. If a paver clicks or moves under your foot, the bedding sand beneath it has been worked out through the empty joint, and there is now a void. Vehicle load on a void is how a small problem becomes a dish. At this stage a re-sand may still hold it, but if several pavers in an area are rocking, the honest answer is usually a localised lift and relay.

Stage three: dishing, ponding and creeping.

Now the base is genuinely moving. Look for a shallow depression along the wheel tracks where the car turns in, and for a puddle that sits after rain where one never used to sit. Water sitting on a pavement is the pavement telling you its levels have changed, and it accelerates everything, because the standing water works the bedding out faster.

The other stage-three sign is creeping. If the joints are opening up wider near the edges of the pavement, or the outermost row is visibly leaning out or has moved off line, your edge restraint has failed or was never there. Without a concrete haunch holding every side in, the pavers push outwards a little more each time a car turns on them, the whole field loosens, and it unravels from the edge inward. This is the single most common corner cut on cheap Geraldton quotes, and it is covered on the buyer's guide. Re-establishing edge restraint is $25 to $45 per linear metre.

The three Geraldton-specific causes.

Once we lift a failed pavement here, it is nearly always one of three things, and which one depends on where you live.

• Not enough base, or badly compacted base. The universal cause. Road base laid too thin, or dumped in one 150mm layer and surface-compacted, leaving the bottom half loose. AS 3727.1 covers what residential pavements actually need, and cheap quotes routinely ignore it.
• Base migrating into coastal sand. Out at Tarcoola Beach, Drummond Cove and Glenfield you are on deep dune sand. Without a geotextile separation layer, the road base slowly works its way down into the sand under repeated load, and the pavement follows it. The fix costs $8 to $15 per square metre at build time and thousands afterwards.
• Soakwell washout. This one is very Geraldton and very underrated. A cracked, undersized or overloaded soakwell discharges into the sand and washes it out sideways, hollowing a void under the pavement above. The tell is a localised, fairly sudden dip near a downpipe or the garage, often after a big winter downpour. Relaying over it without fixing the soakwell is money burnt.

The lip that matters more than it looks.

If you can feel a step between two neighbouring pavers with your foot, take it seriously. AS 1428.1, the access and mobility standard, treats a vertical change of level up to 3mm as fine, 3mm to 5mm as needing a bevel, and anything above 5mm as needing a ramp. It is written for public access ways rather than your front path, but it is a sensible domestic benchmark. A 10mm lip on the path from the carport is exactly what a walking frame, a pram wheel or an 80-year-old's toe catches on, and it is the cheapest thing on this page to fix while it is still one paver.

Retaining walls do not do stages.

Everything above describes a slow, forgiving decline. Retaining walls are not like that. A wall that is bulging in the middle, leaning forward at the top, showing stepped cracking through the block joints, or weeping at its base is telling you something urgent. Almost always it is water: blocked or missing weep holes and drainage mean hydrostatic pressure is building behind a wall never designed to hold it. In Geraldton's severe marine air there is a second cause, internal steel corrosion, and that one gives you almost no warning at all. If your wall shows any of those signs, stop reading and get it looked at. See the retaining wall permit guide for what a compliant rebuild involves.

A worked example: the 8 square metre dip at the garage.

Here is the most common repair we quote. An 8 square metre sunken patch in front of a garage, in Wandina, pavers sound, dish about 30mm deep, right where a downpipe discharges. The lift and relay is $45 to $80 per square metre, so $360 to $640. Straightforward, one day.

But the reason it sank is the soakwell, so the real quote includes sorting that first, and the honest conversation is that relaying without fixing the drainage means we will both be back in two years. Caught two years earlier, when the joints were emptying and before the void formed, that same 8 square metres would have been a $15 to $35 per square metre re-sand, so $120 to $280 instead of $360 to $640, and the soakwell would have been the only real job. Re-sanding the whole 45 square metre driveway at that point would still have been $675 to $1,575, less than a single lift and relay. That is the entire argument of this page in one number. Full rates are on the pricing guide.