Polymeric sand joints that look low, gappy or weedy raise one question: can you just sweep on a second layer? Both makers I checked say no. They want the old sand dug out first, and they do not agree on how deep, or on whether a pressure washer is the tool to do it. This guide sets their instructions side by side, works out what each choice means for a real patio, and explains when joints are due for a redo. If the sand never hardened in the first place, see why polymeric sand stays soft before you decide to dig it out. Part of a bag left over from a touch-up? Our guide to leftover polymeric sand covers storage and how to check it is still usable.
It covers topping up, pressure washing before you refill, how long the sand is meant to last, and what to do when only a few joints have failed. If your problem is the white film after watering, see our guide to polymeric sand haze instead.
Can you apply polymeric sand twice
Not as a top-up over sand that is already in the joint. Alliance Gator’s blog answers a reader who noticed low joints: adding a thin layer of polymeric sand on top of what is there is not ideal, because the original sand can be old, of unknown condition or dirty. Its recommendation is to remove at least 1 inch of the jointing material and then follow the steps for a new installation.
Sika’s data sheet for Evolution Pro Polymeric Sand (version 01.03, December 2025) is stricter on depth. For touch-ups or reinstallation it says to remove all existing sand to full joint depth, or at least 38 mm (1.5 in), before re-sanding. It also says not to partially fill a joint with any other material, and Alliance Gator’s FAQ says the same about filling half a joint with regular sand and putting polymeric sand on top. Alliance calls that topping and warns that water and ice can work into the joint and make the top layer fail.
Two exceptions are worth knowing. If your joints simply look low but are hard and intact, they may already be at the correct height: Alliance says the sand belongs at least 1/8 inch below the chamfer, and 3/16 or 1/4 inch as joints get wider. And if a fresh install did not harden because it was under-watered, Alliance has a different fix: water the surface with a sprinkler for about an hour, open a few small holes in any crust, and only remove and redo the sand if it still has not hardened after a few days of good weather.
Where the makers disagree: depth and pressure washing
| Question | Alliance Gator | Sika Evolution Pro |
|---|---|---|
| How deep to remove old sand | At least 1 inch (blog answer on low joints). At least 1.5 inches in its FAQ for a repair where sand is removed and replaced | All existing sand to full joint depth, or at least 38 mm (1.5 in) |
| Must every bit of old sand go | No. Some material may remain after pressure washing, and in most cases it is permissible to leave it and fill the washed-out areas | Says to remove all existing sand to full depth, or at least 1.5 in |
| Pressure washer to remove it | Yes. Calls it the best way, with a 25 degree tip and at least 3000 psi | No removal method given. Warns against high-pressure jets only when watering new sand |
| Rain and traffic after refilling | Rain safe in 15 minutes to 24 hours depending on the product and base. Walk or drive after 24 hours if dry | 24 hours rain protection, 48 for joints wider than 1/2 in; foot traffic after 24 hours, vehicles after 72 |
The gap between 1 inch and 1.5 inches is worth a minute, because both numbers come from the same company. I would follow the larger one, since it matches Sika and the FAQ’s repair instruction. The word “pressure washer” shows where the two makers really part: Alliance recommends it and gives a tip and a pressure, while Sika’s sheet does not say how to remove old sand and leaves that to you. I could find no statement from either maker that a pressure washer will damage pavers, so a small test in a corner and a check that the bedding sand under the joints stays put are my own cautions, not theirs.
What each choice means on a 10 by 12 foot patio
Take a patio of 6 by 9 inch pavers with 3/8 inch joints, the same example I used in the removal guide. That layout has about 380 feet of joint. Multiply joint length by joint width by depth and you get the volume of sand involved:
| Job | Depth | Sand volume |
|---|---|---|
| A generous top-up | 1/4 inch | about 0.25 cubic feet |
| Remove and refill, Alliance blog depth | 1 inch | about 1.0 cubic feet |
| Remove and refill, Sika and Alliance FAQ depth | 1.5 inches | about 1.5 cubic feet |
That table is the argument against topping up. The top-up saves a few tenths of a cubic foot of new sand, and in exchange you lay fresh polymer over old, dirty sand that the makers say will not bond well. The proper redo means digging every joint out, and it uses about six times the sand of a quarter-inch top-up.
How often polymeric sand needs redoing
There is no fixed schedule in either maker’s paperwork. Alliance Gator’s FAQ says its polymeric sands should last 15 years if the pavers and sand were installed to the stated procedures and the area is maintained, with dirt not allowed to accumulate on the joints. That is a promise about a perfect install, so read it as an upper bound, not a timetable.
Joints are due for work when you see a pattern, not a single gap:
- Isolated washed-out spots at a downspout or at the low corner of a slope often point to water running or pooling there, so look at drainage first, since new sand can wash out the same way.
- Weeds or moss through hard sand are a cleaning job. Alliance’s FAQ says moss and mildew are normally cleaned with a pressure washer, and that if they have been there a long time the sand may be damaged, in which case you remove the damaged sand where it comes out readily, let the area dry and refill.
- Crumbling or loose sand across many joints is a full redo to the depths above.
Refilling a few failed joints
This is the case most people actually have. You do not have to redo the whole patio for a few bad stretches.
- Clear the failed joints with a joint scraper or pick to at least 1.5 inches, or as far as the sand comes out. Alliance accepts leaving hard material that stays put after washing.
- Let the joints dry fully before refilling, since the sand must be applied to dry pavers.
- Fill with the same type of sand. Do not half-fill with another material.
- Sweep the paver faces clean and blow them off before any water touches them. Dust left on the surface is what causes the haze described in our haze guide.
- Water in sections as the product instructs, then keep rain, foot traffic and vehicles off for the times in our setting time guide.
If you need the old sand out across the whole patio, the removal guide walks through hand removal and washing, and the sand guide helps match a product to your joint width.
New sand for the refill
Bags are sold for full installs, so a refill often leaves some over. Alliance says unopened bags kept dry in a low humidity spot should stay usable for up to five years, which is useful if you expect to patch joints again. For a refill I would match the new sand to the old product where you know it, and otherwise use one rated for your joint width. A product I have read the listing for is Alliance Gator G2 Maxx in slate gray. It is in stock, rated 4.3 stars from 74 ratings with 500 or more bought in the past month, and sold by a third-party seller. Check price on Amazon: Alliance Gator G2 Maxx Polymeric Sand. This is an affiliate link (see our disclosure for details).
When to hire it out
If the pavers have shifted, if joints keep washing out after the drainage is fixed, or if the area is a driveway with real load, the cause is often the base, not the sand. A hardscape contractor can lift and reset the pavers and redo the joints in one visit. Find one near you through Angi. This is an affiliate link (see our disclosure for details).
Sources: Alliance Gator FAQ for Gator Jointing Material and the Alliance Gator blog post answering 15 common questions (read on 2 November 2026), and the Sika Evolution Pro Polymeric Sand product data sheet, version 01.03, December 2025. The volumes above are my own arithmetic for the stated patio and do not come from a maker. I did not test any product.
Etienne Basson maintains and repairs his own home, and writes practical guides on choosing the right materials and products for repair and finishing jobs: fillers, sealants, adhesives, and similar. He focuses on what actually works for a specific job, not just a spec sheet.