We talk to a lot of people about polymeric sand, from homeowners doing their first patio to crews who put it down every week. The same questions come up over and over, and when a job goes wrong it's almost always one of three things: the joints were the wrong size, the water was off (too much or too little), or the weather didn't cooperate.
So here are the questions we get most, answered the way we'd answer them on the phone. One ground rule before you start: every brand is a little different, and the bag (or the technical data sheet) always wins. If you want to check a specific product, our TDS and SDS library has them.
How many bags do I need?
This is the big one. Polymeric sand is sold by weight, but it gets used up by joint volume, so "square feet per bag" is all over the place depending on paver size and joint width. A patio of big slabs with tight joints might take half the sand of a small-brick patio with the same footprint.
The most reliable way to figure it is from the length of your joints:
Pounds needed = joint length (ft) × 12 × joint width (in) × joint depth (in) × 0.058
That 0.058 is roughly how many pounds a cubic inch of dry sand weighs. A couple of real-world examples:
- Wide joints, 1-1/2" wide and 1-1/2" deep: about 1.6 lbs per linear foot. A 50 lb bag fills about 30 feet of joint (a 40 lb bag, about 25).
- 4" x 8" brick pavers with 1/4" joints, filled 1-1/2" deep: about 1.1 lbs per square foot of patio. A 50 lb bag covers roughly 45 sq ft (a 40 lb bag, about 35). A 200 sq ft patio works out to about five 50 lb bags once you add the extra below.
Larger pavers mean fewer joints, so your coverage goes up. Use the coverage chart on the bag as a cross-check, and buy about 10% extra. Topping off after the first compaction always takes more sand than people expect, and running out halfway through is worse than having a leftover bag.
Can I use it on concrete cracks, driveways or expansion joints?
No, and this one catches a lot of people. Polymeric sand is made for the joints between pavers and stones that sit on a sand or gravel base. It isn't a crack filler and it isn't grout. On a concrete slab there's nothing for it to lock into. It won't bond to the concrete, so it cracks and washes out.
For cracks and saw cuts in concrete, use a concrete crack sealant or filler. For those old wood expansion strips in a driveway, pull the wood, put in backer rod, and finish with a self-leveling joint sealant.
How wide and deep can the joints be?
- Standard polymeric sand: joints from about 1/8" up to around 1" wide.
- Wide-joint (XL) sand: made for flagstone, fieldstone and bigger gaps. The max width varies a lot from product to product, so check the bag.
- Depth: most brands want at least 1", and several (Gator Super Sand G2 and Maxx G2, for example) call for 1-1/2" minimum. Going the full depth of the paver is even better. Shallow fills are the ones that crack and pop out.
- Really wide gaps (3" and up): fill the bottom with gravel or base material, compact it, then use polymeric sand for the top 1-1/2" to 2".
Do I have to dig out the old sand or gravel first?
Yes. Clean the joints out to at least 1" to 1-1/2" below the top of the paver (deeper if your product calls for it). The sand needs that depth to form a solid band that holds together.
It's fine sitting on top of setting sand or compacted base. What it can't do is sit on loose pea gravel or pebbles. They shift underneath it, the sand sinks, and the joint cracks. For the same reason, polymeric sand won't lock a loose pebble or river rock path together.
Do I mix it with water first?
No. Standard polymeric sand goes in dry and gets watered after. (A few specialty products, like some air-cure and resin-based sands, have their own steps, so read the bag if you're using one of those.) Here's the basic process:
- Make sure the pavers and joints are completely dry.
- Pour the sand on and sweep it into the joints.
- Run a plate compactor with a rubber pad over it (or tamp by hand on small jobs) to settle the sand. Top off the joints and repeat until they're full.
- Get every bit of loose sand and dust off the paver surface. Sweep with a soft broom, then go over it with a leaf blower on low, held at a shallow angle so you don't blow sand out of the joints.
- Water it with a shower or mist setting, not a jet. Don't flood it. Most bags have you wet it, wait a few minutes, and wet it again. Follow whatever your bag says.
Step 4 is the one people rush, and it's the one they regret. Any sand left on the surface when the water hits turns into a haze that's a real pain to get off.
What kind of weather do I need?
- Rain: plan on 24 hours of dry weather after you install. If rain is coming in the next few hours, wait for a better day. Some newer fast-set sands are rain-safe in as little as 15 minutes after watering, but check the bag before you count on that.
- Dry conditions: the base and joints need to be dry, not just the surface. If the sand underneath is wet, the polymer activates too early and won't set right.
- Temperature: the sweet spot is roughly 50°F to 80°F. When it's over 90°F, work in the morning or evening and keep the pavers out of direct sun while you're working.
- Cold: don't install if it's going to freeze in the next 24 to 48 hours. Minimum temperatures vary by product, so check the label.
How long until it hardens and I can use it?
- Foot traffic: about 24 hours.
- Cars on a driveway: about 48 to 72 hours.
- Full cure: several days, and longer when it's cool or humid.
If the joints (especially wide ones) still feel soft or spongy after a week, they probably got too much water or went in too shallow. Let them dry out completely. If they still won't firm up, the fix is to dig them out and redo them.
Does water drain through it? Will it wash out?
Once it cures, it sheds most water off the surface, and some products let a little seep through. If it's installed right, it won't wash out in a heavy rain. It also stays slightly flexible, so the pavers can move a bit with the seasons without cracking the joints.
You can pressure wash once it's fully cured, but go easy. Use a fan tip, keep the pressure moderate, and hold the wand at an angle. Don't point it straight down into the joints.
Does it stop weeds, ants and moss?
It does a good job keeping weeds from coming up from below and keeps ants from tunneling through the joints. What it can't stop is windblown seeds or moss taking hold on a dirty, shady surface. Regular sweeping goes a long way. If moss shows up, use a moss killer that's safe for pavers. And kill off any existing weeds and moss before you install.
Do I need to seal it? Can I paint it?
You don't have to seal, but a good sealer helps with color and stain resistance. Most sealer manufacturers say to wait about 30 days after installing polymeric sand, but check your sealer's label. As for paint, skip it. Paint won't hold up on a sand joint.
How do I get haze or dried sand off my pavers?
Use a polymeric haze remover or an efflorescence cleaner made for pavers, and scrub with a stiff brush. Always test a small spot first. If your joints look lighter than the color on the bag, there's usually dried dust sitting on them, and a haze remover often brings the color back. We go into more detail in how to remove polymeric sand haze.
Is it safe around plants, pools and pets?
Once it's cured, it's inert. During the install, keep the dry dust off your plants, and wear a dust mask while you pour and sweep, since the dust contains fine silica. Keep pets and kids off the area until it's cured.
It works fine around pools. Just rinse off pool splash-out now and then, and don't let salt water sit and soak the joints. It's not meant for fish ponds, tanks or anything that stays underwater.
Will it work on my pavers?
- Concrete pavers, clay brick, Chicago brick: yes.
- Flagstone, slate, fieldstone, travertine: yes, but use a sand rated for natural stone and wide joints. Some popular sands (Gator Maxx G2 and SRW Z3, for example) aren't recommended for flagstone.
- Thin porcelain pavers (2 cm): only if the joints are deep enough and the pavers sit on a sand or gravel base, not on pedestals or mortar. There are also sands made specifically for porcelain.
Quick install checklist
Print this out or keep it on your phone for install day:
- Joints cleaned out at least 1" to 1-1/2" deep (or whatever your bag calls for)
- The right sand for your joint width and paver type
- Bags figured from linear feet of joint, plus 10%
- Pavers, joints and base completely dry
- 24 hours of dry weather in the forecast, ideally 50°F to 80°F
- Sand swept in, compacted and topped off
- Surface blown completely clean
- Watered in gentle stages, not flooded
- Kept off for 24 hours on foot, 48 to 72 hours for cars
Still have a question?
Every job is a little different. Send us your paver type, joint width and depth, and square footage, and we'll tell you which sand makes sense and how many bags to order. You can shop the full lineup at PolymericSandStore.com.