Empty joints let pavers shift, weeds root and water run into the base. This guide covers why joint sand disappears, the signs it is time to re-sand with polymeric sand, the steps in order, and the weather and mistakes that decide whether it holds.
In This Article
Why joint sand washes out
Joint sand is usually the first part of an interlock surface to wear out. It keeps the pavers from shifting against each other, and every force on the surface works on it.
- Water. Rain sheeting across a slope, a downspout emptying onto the stones and a sprinkler aimed at the edge all carry sand away.
- Cleaning. A close, hard jet blasts sand out in seconds. A wide fan tip held well back keeps most of it in (see the interlock cleaning guide).
- Frost. Freeze-thaw cycles are common from November to April here. Ice and slight movement loosen the sand, and meltwater flushes it out.
- Ants. They carry grains up into mounds and leave hollow joints.
Signs your joints need re-sanding
Check on a dry day with a putty knife.
- Low sand. Joints should be full to about the bottom of the bevelled edge. A visible dark bedding layer or a deep gap means they are low.
- Growth. Weeds and moss need a foothold of dirt, which collects in low or loose joints.
- Ant mounds along the joint lines.
- Soft joints. Old polymeric sand that is cracked, powdery or scrapes out easily has failed.
- Shifting stones. Pavers that click or rock underfoot. If a whole patch has sunk, the base is the problem and sand will not fix it.
If ants are active, treat the nest first, and read Ontario's current pesticide rules before buying a product.
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Regular sand or polymeric sand?
Regular jointing sand is loose and cheap. Polymeric sand is fine sand blended with binders that harden when water activates them, leaving a firm, semi-rigid fill.
| Compared | Regular jointing sand | Polymeric sand |
|---|---|---|
| Washout | Moves with rain, jets and frost | Resists all three far better once cured |
| Weeds and ants | Easy for both | Harder for both to establish |
| Topping up | Sweep in more, any time | Loose or crumbling fill must come out to the depth on the bag first |
Choose polymeric sand for driveways, patios and walkways with a sound base and ordinary joint widths. Choose regular sand where joints stay wet, or ask about a fine-joint product for very narrow ones. Switching from regular to polymeric is common at a re-sand, since the old sand has to come out anyway. Permeable pavers are the exception: their joints hold clean stone chips so water can drain, and polymeric sand would block them. Ask the installer if you are unsure.
The steps, in order
- Clear the joints. Pull weeds, then vacuum or pick out loose sand and debris to the depth on the bag, often 25 mm (1 in) or more.
- Let everything dry. Pavers and joints must be dry through. Allow a day or two after washing or rain, longer in shade, and probe a joint with a screwdriver. Damp, cool sand means wait.
- Sweep the sand in. Work a small area at a time, pushing the sand a short distance so the mix stays even and the joints fill.
- Compact. Many data sheets call for a plate compactor with a protective pad, and a hand tamper or rubber mallet may do for small repairs. Top up the dips and compact again.
- Clear every grain off the faces. Sweep, then use a leaf blower on low. Sand left on the stones becomes haze.
- Mist to activate. Use a shower setting, one small section at a time, in short passes, and follow the bag on how much water. Stop when water begins to stand on the joint, do not flood it, and blow pooled water off the stones before it dries.
- Cure. Keep people, pets, cars and sprinklers off for the time on the bag.
Weather limits and the mistakes that cost the most
Limits differ between brands, so read the bag. Typically that means dry pavers, no rain for a day or more after activation, a temperature above the stated minimum while it cures, and sprinklers off. After the spring thaw the bedding can stay saturated, so joints may stay damp for days after the surface looks dry. Cold nights and dew in April and October can undo a mild afternoon, and hot sun can dry the surface before the sand has activated, so work in small sections.
| Mistake | What happens | How to avoid it |
|---|---|---|
| Sand left on the stones | A hard, whitish haze where binder cures on the surface | Sweep and blow the faces clean before any water |
| Damp joints | Sand clumps, will not flow down and sets unevenly | Probe the joints first |
| Too much water | Binder washes out, joints stay soft and runoff leaves a film | Mist in short passes and stop at standing water |
| Too little compaction | Sand settles after misting, leaving shallow joints | Compact twice and top up |
Cured haze will not brush away. Hardscape suppliers sell cleaners made for it, and a test patch comes first.
Where re-sanding fits between cleaning and sealing
The usual order is wash, dry, re-sand, cure, then seal. Wash gently, because a hard jet undoes the work. Re-sand before sealing: a sealer can only firm the top of joints that are full, and a coat over empty gaps locks them in. Then give the sand its full cure. Makers disagree on how long, and some data sheets ask for a month before sealing or pressure washing. Follow the longer of the sand maker's and the sealer maker's waits.
D&D Home Services does interlock and paver cleaning, re-sanding with polymeric sand and sealing around Kitchener-Waterloo, with free quotes confirmed in writing before work begins. Tell any crew what the pavers are and where the sand has gone, and ask how they will handle haze and cure time. The interlock maintenance guide suggests a yearly routine.
Key Takeaways
- Rain, hard-jet cleaning, frost and ants strip joint sand, so low joints, weeds and shifting stones mean it needs replacing.
- Polymeric sand resists washout and weeds better than regular sand but needs dry joints and dry weather. Permeable pavers take clean stone instead.
- Clear, dry, fill, compact twice, blow every grain off the stones, mist lightly, then cure for the full time on the bag.
- Re-sand before sealing, and wait for both the sand maker's and the sealer maker's cure times.
Sources & References
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