Last Updated on October 20, 2026 by Umar Farooq
Weeds growing through polymeric sand are almost never coming up through the hardened sand. They are rooting in the dust, leaf grit and seeds that settle on top of the joint, or in a spot where the joint is thin, cracked or washed out. Polymeric sand reduces weeds, but none of the sources I opened claim it stops them. Work out which of four causes you have, then fix that joint, not the whole patio.
One of the pages I read puts it plainly: polymeric sand "can reduce weed growth between pavers, but it cannot guarantee a permanently weed-free patio."
Weeds growing through polymeric sand: read the root
Pull one weed and look at where the root sits. That answers most of the question.
| What you see | Likely cause | The fix |
|---|---|---|
| Weeds in a thin film of soil on top of a hard joint | Debris and seeds settled on the surface | Sweep or blow the joints clean, pull while small |
| Weeds in a low, crumbly or washed-out joint | Joint too shallow or sand lost | Clean out and refill the section |
| Weeds in cracks along the paver edges | Joint cracked or the pavers moved | Fix the movement, then re-sand |
| Weeds mostly along the outer rows | Freeze-thaw and edge movement | Check the restraint, re-sand the edge |
I did not find a study that counts how often each cause happens. The sources agree on the list, not the ranking.
The top of the joint is the seed bed
Two of the pages describe the same mechanism. Seeds blow in, and dirt, pollen, grass clippings and leaves collect on the surface and break down into a thin layer of soil. Paver Protector says this layer also holds moisture in the sand and weakens it. Hard sand underneath does not stop a seed germinating in that layer.
So the first habit is a broom or leaf blower, not a spray bottle. Sweep after mowing. (A patio you sweep is a patio the weeds have to apply to.)
A thin joint grows weeds sooner
Polymeric sand needs depth to harden properly. The Alliance Gator SuperSand G2 data sheet calls for a minimum joint depth of 1 1/2 inches and finished sand at least 1/8 inch below the paver top. Techniseal's HP NextGel sheet gives the same 1.5 inches. Other pages give different joint widths: House Digest says polymeric sand works best in gaps from 1/4 to 1 1/2 inches wide, while the Gator sheet allows 1/8 to 2 inches. Follow the data sheet on your bag.
Three installation mistakes come up repeatedly:
- Sand not packed deep enough, so the bottom of the joint stays loose.
- Too little water, so the joint does not set at depth.
- Too much water, which House Digest says separates the polymers from the sand and weakens the joint.
I covered the mechanics in how to apply polymeric sand and the wider failure list in polymeric sand problems.
Movement and water that no new sand will fix
Kelly Masonry's guide says polymeric sand "cannot correct an unstable base, failed edge restraint, settlement, or moving pavers." Standing water, poor drainage and shade support moss and weeds too. If the joints keep cracking at the same spot, resanding is a bandage over a base problem; see how to keep pavers from moving and patio drainage.
Fix the weeds without redoing the patio
The sources disagree on one step, so here is the sequence I would use and where the disagreement sits.
- Pull small weeds early. Kelly Masonry notes this also shows you where the sand is failing.
- For a few stray weeds in a hard joint, Tussey Landscaping advises a targeted weed killer rather than digging, because digging disturbs the hardened sand and can restart the cycle. Read the product label first; our guide to removing weeds from pavers covers the options.
- For a joint that has failed, remove the old material to the depth the replacement product needs. Kelly Masonry warns that sand added over failed material may not last.
- Do not blast the joints. Tussey's five-step fix includes power washing out the old sand, and Kelly Masonry warns against concentrated high pressure in the joints because it removes joint material. They disagree on degree, and I side with the gentler read: wide tip, low pressure, test a patch (see our power washing guide).
- Let it dry, then refill to the data-sheet depth and activate the sand as directed. Re-sand pavers has the full steps.
If you have permeable pavers, Kelly Masonry cautions against polymeric sand and sealers because they can restrict water infiltration. Check the manufacturer first.
Will sealing keep weeds out?
Paver Protector says sealer keeps the surface cleaner and, where it floods the joints, adds binding strength. Kelly Masonry says a sealer is not a weed-control substitute. Both can be true. A sealer firms a joint; it does not make dust stop landing on it. See sealing paver joints.
How often to redo the joints
Tussey recommends re-sanding every 3 to 5 years. That is a contractor's rule of thumb, not a manufacturer figure. Replace the sand when it is visibly low, cracked or loose, not when the calendar says so.
Keep the top clean and the joint full
Weeds growing through polymeric sand are a housekeeping signal, not a verdict on the product. Sweep the seed bed away, keep the joint deep enough to harden, fix any movement or water underneath, and treat only the failed joints. Polymeric sand is not a force field. It just gives the weeds a harder place to start.
FAQ
Can weeds grow through polymeric sand?
Not through hardened sand, mostly. They root in dust and debris on top of the joint or in thin, cracked or washed-out spots. Sources say polymeric sand reduces weeds but does not stop them.
Why are weeds coming up in my polymeric sand joints?
Common causes are seeds settling in surface debris, joints that were not packed deep enough, too little or too much water at activation, and movement or freeze-thaw cracking along the edges.
Can I put weed killer on polymeric sand?
Tussey Landscaping advises a targeted weed killer on stray weeds rather than digging them out, so the hardened sand is not disturbed. Follow the label for hard surfaces and avoid runoff into beds.
Should I power wash the joints to remove weeds?
Be careful. One contractor includes power washing in a full redo, while another warns that concentrated high pressure removes joint material. Use a wide tip at low pressure and expect to re-sand.
How long does polymeric sand last before weeds return?
One contractor suggests re-sanding every 3 to 5 years. Treat that as a rule of thumb and redo joints when they are visibly low or cracked.
