What it is
50-pound bag of polymeric joint sand — fine sand mixed with a polymer binder that hardens when wet. Sweep it into the joints between pavers or flagstone, mist with water, and the joint locks. Stops weeds, ants, and washout in one pass.
What it's for
Every paver patio, every paver driveway, every flagstone install — the joints need polymeric sand. Without it, the joints fill with regular sand or dirt and become a launching pad for weeds, ant colonies, and erosion. With it, the joints stay clean for 5-7 years before they need a refresh.
Three install scenarios:
- New paver/flagstone install — sweep in polymeric at install time as the final step. Wet it down per the bag instructions.
- Joint refresh on existing hardscape — pressure-wash the joints first (blow out the old sand and weeds), let everything dry, then sweep in fresh polymeric.
- Repair of washed-out joints — sweep into any joints where the original sand has migrated out, mist, done.
How much do I need
Coverage depends on joint width. For standard tumbled-paver joints (1/8" - 3/16"):
| Patio size | Bags (pavers) | Bags (flagstone, wider joints) |
|---|---|---|
| 100 sq ft | 1 | 1-2 |
| 200 sq ft | 2 | 3 |
| 400 sq ft | 4 | 5-6 |
| 800 sq ft | 8 | 10-12 |
Flagstone uses more because flagstone joints are wider and more variable. The flagstone patio wizard computes the bags for you given your patio size.
How to install it (key steps that matter)
- Joints must be dry before sweeping the sand in.
- Sweep sand into joints with a stiff broom. Top off — joints must be full to the top.
- Use a plate compactor to vibrate the sand down into the joints (skip on flagstone, do on pavers).
- Brush off ALL the excess from the paver surfaces — any polymeric left on the surface will cure into a haze.
- Mist with a fine spray (not a hard stream). Soak the joints just enough to activate the polymer. Don't flood.
- Don't walk on it for 24 hours.
Trade-offs vs regular sand
Regular paver sand is cheap and easy. It also washes out in the first hard rain, lets ants tunnel through, and lets weed seeds germinate in the joints. Polymeric is 3x the cost and 10x the lifespan.
Buying tips
- Don't buy more than one season's supply. The polymer binder can absorb humidity in storage and partially activate in the bag.
- Match the bag color to your hardscape — comes in tan and gray.
- For a 200 sq ft paver patio, plan on 2 bags plus a half-bag of margin for the corners you'll miss the first sweep.
Contractor notes
Volume break at 20 bags. Bundle quote available with paver/flagstone orders.