The joints between pavers do more work than most homeowners realize: they lock the field together, keep weeds and ants from colonizing the base, and decide whether your patio drains or puddles. When people ask me about paver grout, they are usually picturing bathroom grout in a bag, but outdoor jointing is its own product world with four real options — plain sand, polymeric sand, resin/epoxy jointing compounds, and true mortar — and the right one depends entirely on how the pavers were laid (sand-set versus mortar-set on concrete), the joint width, and your climate. Pick wrong and you get washouts, weeds, or a cracked white mess by spring. Here is how the options actually compare, with the install rules that make each one last.
Part of our Tile & Grout guide — explore the full guide →
- First question: what are your pavers sitting on?
- Option 1: Plain joint sand — cheap, honest, high-maintenance
- Option 2: Polymeric sand — the default for sand-set patios
- Option 3: Resin and epoxy jointing compounds — premium flexibility
- Option 4: Mortar joints — for rigid, slab-based work only
- Side-by-side comparison
- Maintenance that keeps joints full
- Fixing joints that already failed
First question: what are your pavers sitting on?
This single fact eliminates half the options. Sand-set (flexible) installations — pavers on compacted gravel and bedding sand, the standard for interlocking concrete pavers — move slightly with seasons, so they need jointing that flexes: sand, polymeric sand, or flexible resin compounds. Rigid mortar in a flexible system cracks the first winter, guaranteed. Mortar-set (rigid) installations — flagstone or brick bedded in mortar over a concrete slab — do not move, so they can take true mortar joints, and sweep-in sands are actually the poor fit here because wide, deep joints over concrete want a structural fill. Know which you have before buying anything.
Option 1: Plain joint sand — cheap, honest, high-maintenance
Washed, angular concrete sand swept into the joints is the traditional interlock jointing and still what many pros use under the right conditions. It costs almost nothing ($5 to $10 per 50-pound bag), flexes perfectly, and refreshes in an hour whenever needed. Its weaknesses are the famous ones: it washes out of joints on slopes and gutters, weeds seed into it, and ants mine it. Plain sand makes sense for tight-jointed (under 1/4 inch) interlocking pavers on flat sites, and for anyone who would rather sweep in $10 of sand every couple of years than fight a failed fancy product. Use coarse, angular sand — never fine play sand, which migrates and holds moisture.
Option 2: Polymeric sand — the default for sand-set patios
Polymeric sand is graded sand blended with polymer binders that activate with water and cure into a firm-but-flexible joint. It resists washout, dramatically slows weeds and ants, and stays put on slopes. Bags run $20 to $50 for 40 to 65 pounds, covering roughly 50 to 100 square feet depending on paver size and joint width. This is my default recommendation for concrete-paver patios, walkways, and driveways with joints from 1/8 inch up to the product’s rated maximum (often 1 to 2 inches for the newer formulas, and 4 inches on some wide-joint products).
Polymeric sand earns its bad reviews only through installation shortcuts, because the process is unforgiving in exactly three places:
- Bone-dry pavers and joints, with no rain forecast for 24 hours. Moisture activates the polymer; damp joints cause weak, crumbly cure.
- Complete surface cleanup before watering. Sweep diagonally, compact or tamp the sand into joints, refill, then blow every grain of dust off the paver faces with a leaf blower on low. Any residue left becomes polymer haze bonded to the paver — the number one polymeric complaint, and it is pure prep failure.
- Controlled watering: a gentle shower in stages until the joint is saturated to full depth but never flooding, which floats binder onto the surface. Then let it cure per the bag, typically 24 hours before foot traffic and up to 48 to 72 before vehicles.
Fill depth matters too: joints should be full to within about 1/8 inch of the chamfer, over joints at least 1.5 inches deep. Expect a well-installed polymeric joint to last 5 to 10 years before topping up.
Option 3: Resin and epoxy jointing compounds — premium flexibility
A newer category imported from the European market: ready-mixed, air-curing resin-bound jointing compounds (and two-part epoxy versions) that you sweep into wet joints. They stay slightly flexible, are essentially weed-proof, tolerate pressure washing, and — the killer feature — most install on pre-wetted pavers in damp weather, the exact conditions polymeric sand forbids. Many are also self-compacting into narrow joints. The tradeoffs are price and permanence: $40 to $90 per tub covering 30 to 70 square feet, minimum joint widths (commonly 1/4 inch or wider and 1 inch deep), and once cured they are difficult to remove if you ever need to lift pavers. For natural stone patios with irregular joints, and for shaded, damp sites where polymeric never gets its dry window, resin compounds are the quality answer.
Option 4: Mortar joints — for rigid, slab-based work only
True mortar (or sanded exterior grout rated for the application) belongs on mortar-set flagstone and brick over concrete. Joints are packed with a grout bag or pointing trowel, struck, and cured damp. Done right it is the most formal, most permanent look, and it handles wide irregular flagstone joints no sweep-in product can. Done over a sand-set base, it cracks — repeat that to any contractor who proposes it. Materials are cheap (a few dollars per square foot), but the labor is the highest of all options, and in freeze-thaw climates even proper mortar joints need occasional repointing; hairline cracks let water in, ice does the rest. Use a mortar with appropriate air entrainment outdoors in the north, and keep sealed expansion joints where the slab has them.
Side-by-side comparison
| Jointing | Base required | Cost/100 sq ft (material) | Life | Weeds/ants | DIY difficulty |
|---|---|---|---|---|---|
| Plain sand | Sand-set | $10–$20 | 1–3 yrs per top-up | Poor | Trivial |
| Polymeric sand | Sand-set | $40–$100 | 5–10 yrs | Good | Moderate, weather-dependent |
| Resin compound | Either (check label) | $100–$250 | 10+ yrs | Excellent | Easy but exacting on width/depth |
| Mortar | Concrete slab only | $30–$80 + heavy labor | 10–25 yrs w/ repointing | Excellent | Skilled |
Maintenance that keeps joints full
Whatever paver grout you choose, the maintenance rules rhyme. Sweep the patio rather than power-blasting it: a pressure washer aimed into joints excavates plain sand instantly, chews polymeric within a year or two of cure, and even scours resin joints at close range — if you must pressure-wash the paver faces, keep a 30-degree or wider fan tip, hold 12 inches off the surface, and travel across the joints, not along them. Top up low spots as soon as you notice them, because a half-empty joint collects seed and silt, and that organic layer is what weeds actually germinate in. Re-sand or re-poly after any paver repair. And in ice country, use plain rock salt sparingly and skip magnesium chloride blends on new joints for the first winter; fresh polymeric and mortar both cure stronger when their first freeze season is a gentle one.
Fixing joints that already failed
Washed-out sand: blow out debris, re-sweep with polymeric on a dry forecast. Crumbling old polymeric: remove the top inch minimum — a pressure washer on a fan tip or a joint scraper does it — because new polymeric over failed polymeric delaminates; then reinstall properly. Cracked mortar joints on a slab: grind or rake the cracked runs, vacuum, and repoint. Polymer haze on paver faces: light haze often weathers off over a season; heavy haze needs a dedicated polymeric-haze cleaner and scrubbing, so prevention (the leaf blower step) remains the better plan. Weeds in any joint type: kill and pull, then top the joint up — weeds root in the joint fill, not under the patio, so full joints are the actual weed strategy.
My plain recommendation set, after years of patio callbacks: interlocking concrete pavers on sand get polymeric sand installed on a dry weekend with religious blower work before watering. Natural flagstone with fat irregular joints gets a resin jointing compound, or mortar if it is set on a slab. Flat, tight-jointed paths owned by patient people get plain sand and a free Saturday every other year. And any bid that proposes mortar or bagged tile grout over a flexible sand-set patio gets a polite no, because the freeze-thaw cycle has never once lost that argument. Match the paver grout to the base and the weather window, fill the joints completely, and the patio’s edges will still be crisp when the furniture has faded.
