Deciding what to put between pavers comes down to five options. Polymeric sand suits most jointed paving on a flexible base, washed sand suits permeable and low-traffic areas, gravel suits wide informal joints, mortar suits paving laid on a rigid base and nothing else, and resin compounds suit wide or damp joints where sand will not hold.
The variable that decides between them is not the look. It is the width of your joints and what sits underneath the paving.
The five joint fillers compared
| Filler | Best for | Weed resistance | Permeable | Joint width | Removable later |
|---|---|---|---|---|---|
| Polymeric sand | Jointed paving on a flexible base | Good while intact | Limited once cured | Manufacturer-specified range | Difficult |
| Washed or kiln-dried sand | Permeable paving, low traffic, lift-and-relay areas | Poor | Yes | Tolerant of most widths | Easy |
| Gravel or crushed stone | Wide informal joints, gravel-set paths | Moderate | Yes | Wide joints only | Easy |
| Mortar or cement | Paving laid on a rigid concrete base | Good | No | Wide and narrow both workable | Very difficult |
| Resin and joint compounds | Wide or damp joints, and stone that sand will not hold | Good | Depends on product | Widest tolerance | Difficult |
Read the last two columns together. Permeability and reversibility are the two things people rarely think about at jointing time and always think about later.
How joint width decides your filler
Measure your joints before you buy anything. A joint that is too narrow for the product will bridge rather than fill, and a joint that is too wide will crack as it cures or wash out as soon as it rains.
Narrow joints, the kind you get on sawn pavers laid tight, generally need a fine sand and will not accept gravel or a coarse compound at all. Standard joints on regular-format paving are the range polymeric sand is designed around, and they are the easiest to fill well. Wide joints, which is what you usually get on crazy paving and on hand-split cobble work, sit outside most polymeric sand specifications and are better served by gravel, a resin compound or mortar where the base allows it.
Irregular joints are the awkward case. A crazy paving surface in natural stone can vary from a few millimetres to well over twenty across the same area, which means part of it may sit inside a product’s stated range and part may not. Measure at several points, not one.
Polymeric sand
Polymeric sand is a jointing sand blended with binders that harden when activated with water, so the joint sets in place instead of staying loose. It resists weeds, ants and washout better than plain sand, and for most residential paving on a compacted base it is the default answer.
Its weaknesses are specific rather than general. It needs a dry window to cure, so rain part way through the process ruins the joint. It only works inside the joint width the manufacturer states. And once it has cured, removing it is a mechanical job rather than a sweep. Get the application of polymeric sand right and it will hold for years; get the timing wrong and you will be redoing it.
Washed and kiln-dried sand
Washed or kiln-dried jointing sand is plain fine sand swept into the joint and left loose. It is the cheapest option, it goes down in an afternoon and it can be topped up at any time with no preparation.
Loose is both the drawback and the point. It washes out in heavy rain, tracks out underfoot on a busy path, and lets weeds seed in the joint, so it needs topping up periodically. In return it keeps the paving permeable and it lets you lift and relay individual units without breaking anything, which matters on paving over services or on any surface you expect to adjust.
Use washed sand where permeability or reversibility is worth more to you than a maintenance-free joint.
Gravel and crushed stone
Fine gravel or crushed stone fills wide joints that sand would simply wash out of, and it suits informal settings where the joint is meant to read as part of the design rather than disappear. Stepping stones set through a gravel bed, wide-jointed flagstone paths and courtyard paving with a deliberate open joint all work this way.
Choose the gravel size against the joint. Too fine and it behaves like sand and migrates, too coarse and it will not seat. It stays fully permeable, which is often the reason for choosing it, and it is easy to top up or remove.
Mortar and cement
Mortar and cement joints are rigid, and rigid is the whole story. They lock the paving into a single surface, they resist weeds completely and they will not wash out.
They also crack. Any movement in the paving or the ground beneath it goes straight into the joint, because there is nothing left to absorb it, and a cracked mortar joint lets water in without letting it drain. That is why the honest answer is narrow: mortar joints are suitable where the paving is laid on a rigid concrete base and unsuitable where it is laid on a flexible sand or aggregate base. On a flexible base they will fail, and they are the hardest of all the options to reverse when they do.
If your paving is bedded on sand or crushed rock, this is not the filler for it.
Resin and joint compounds
Resin-based jointing compounds are two-part or pre-mixed products brushed into the joint, and they sit at the top of the price range. What you buy for the extra cost is tolerance: they handle wider joints than polymeric sand, several are rated for application into damp joints, and they hold in situations where sand-based products will not.
They suit wide-jointed natural stone, restoration work and jobs where the weather window will not cooperate. Some are permeable and some are not, so check the product rather than assuming.
What stops weeds growing between pavers?
Weeds grow in paver joints because seed lands in the joint, not because it comes up from underneath. That is the single most useful thing to know, because it means the fix is at the surface.
- A full, firm joint. A joint filled to depth with polymeric sand, resin compound or mortar gives seed nowhere to lodge. Most weed problems are actually joint problems.
- Regular sweeping. Organic matter collecting on the paving is the seedbed. Sweeping removes it before it composts into the joint.
- Good drainage. Standing water keeps joints damp and germination easy. Fixing falls and drainage does more than any treatment.
- Prompt removal. Pulling weeds before they seed stops the next generation. Once a joint has seeded, you are treating the problem annually.
Salt, boiling water and vinegar all get recommended online. Salt in particular can damage stone and affect surrounding planting, so it is worth being cautious about anything you pour into a joint on natural stone.
Filling joints in natural stone paving
Natural stone differs from concrete paving in two ways that affect this decision.
Joints are often wider and less regular, particularly on crazy paving, hand-split cobbles and reclaimed material, so the width range you are working to is a range rather than a number. That pushes some projects towards gravel or a resin compound and away from polymeric sand.
Surface finish is the other. Tumbled, sandblasted, flamed and split-face surfaces hold residue in a way a smooth concrete paver does not, so any product that cures on the face is harder to clean off. The control is the same whichever filler you use: clear every grain off the surface before you introduce water, and work in sections small enough to clean properly.
Colour is worth a thought too. A pale jointing sand against dark bluestone reads as a strong grid, and a matched tone lets the paving read as one surface. Neither is wrong, but it is easier to decide before the sand is in the joint than after.
How to refill paver joints on existing paving
- Clear the old joint out. Remove loose sand, debris and weeds to the depth the new filler needs. A joint rake or a stiff blade works for most jobs.
- Wash the surface and let it dry fully. Residue in the joint stops a new filler bonding, and damp joints cause problems with polymeric and resin products.
- Check the joint width now that it is clear. This is the point to confirm the filler you bought actually suits the joint you have.
- Sweep the filler in. Work diagonally across the paving rather than along the joint lines so you fill rather than skim.
- Compact and top up. Joints drop on first compaction. Refill and repeat until they hold level.
- Clean every grain off the surface before any water goes near it.
- Activate or water only if the product requires it, at the rate the manufacturer states, and keep traffic off until it has cured.
Do the cutting before the jointing, not after. If you are still fitting pieces, the method you use to cut the pavers determines your joint allowance, and cutting to the exact measurement leaves you nothing to joint with.
Frequently asked questions
1. What is best to fill the gaps between pavers?
Polymeric sand is the best general answer for standard-width joints on paving laid over a flexible base, because it resists weeds and washout while keeping a small amount of flex. Wide or irregular joints are better filled with gravel or a resin compound, and paving on a rigid concrete base can take mortar. Match the filler to the joint width and the base, not to the look.
2. What is the best thing to use in between pavers?
For most residential patios, paths and driveways, polymeric sand. For permeable paving or any surface you may need to lift, washed sand. For wide informal joints, gravel. For a rigid concrete base, mortar. For wide joints or damp conditions where sand will not hold, a resin jointing compound.
3. Do you have to put anything between pavers?
Yes, on any jointed paving. An empty joint lets the units move independently, collects water and debris, and gives weeds an ideal seedbed. Jointing is what turns a set of individual pavers into a stable surface. The exception is stepping stones set into lawn or gravel, where there is no continuous joint to fill.
4. What can I put between paving stones to stop weeds?
A joint filled firmly to depth is the most effective weed control, because weeds in paving germinate from seed landing in the joint rather than growing up from below. Polymeric sand, resin compounds and mortar all deny that seedbed. Loose sand does not, so a sand-jointed surface needs regular sweeping and topping up instead.
5. Can you use cement between pavers?
Only where the paving is laid on a rigid concrete base. On a flexible sand or aggregate base, cement and mortar joints crack as the paving moves, and a cracked rigid joint traps water without draining it. Cement joints are also the hardest to reverse, so it is worth being certain about the base before committing to them.
6. How often do paver joints need refilling?
Loose sand joints need topping up periodically, particularly after heavy rain or pressure washing. Polymeric sand, resin and mortar joints should hold for years, but they are worth inspecting annually and repairing in isolated spots rather than waiting for a whole surface to fail. Drainage and regular cleaning extend joint life more than the filler choice does, which is part of the wider job of maintaining stone paving in Australian conditions.
Choosing a filler for your project
Measure the joints, work out what the paving is bedded on, and decide whether you would rather have a joint that never needs attention or one you can undo. Those three answers narrow five options to one.
If the paving is not laid yet, the joint width is partly set by the format and finish you choose, so it is worth raising with your supplier while you are still handling natural stone paving samples rather than after the pallet arrives.
