Resin-Bound Stone Calculator

How the resin-bound calculator works

Resin-bound surfacing is a mix of dried stone and a polyurethane resin binder, trowelled onto a sound base in a single smooth, permeable layer. This calculator works out how much of each you need. It multiplies the area by a coverage rate for the resin and another for the aggregate, and scales both for your laying depth, because suppliers quote their rates at one standard depth: 18 mm in metric and 3/4 in on the US side.

With the US defaults, 430 ft² at 3/4 in takes 430 × 6.2 = 2,666 lb of aggregate (1.33 US tons) and 430 × 0.43 = 184.9 lb of resin. The metric default, 40 m² at 18 mm, takes 40 × 30 = 1,200 kg of aggregate and 40 × 2.0 = 80 kg of resin. At a different depth both scale in proportion: the same 40 m² at 15 mm needs 1,000 kg of aggregate and 66.7 kg of resin.

Where the default rates come from

Resin-bound is sold as kits, a resin pack matched to a fixed weight of stone, so the rates come from what suppliers say one kit covers. SEK's ResinScape technical data sheet, for the US market, gives one kit with 200 lb of aggregate covering 32.3 ft² at 3/4 in (18 mm) for residential driveways, 38.7 ft² at 5/8 in for foot traffic only and 23.7 ft² at 1 in for light commercial vehicles. That's 200 ÷ 32.3 = 6.2 lb of aggregate per ft², the US default.

UK kits say much the same in metric. BoundWorx kits hold 7 kg of resin, 100 kg of aggregate and 6.25 kg of sand, and cover 3.50 m² at 18 mm: about 30.4 kg of stone and sand and 2.0 kg of resin per m². Daltex gives 3.55 m² at 18 mm for a 7.5 kg resin mix at a resin ratio of 7.1%, which is about 2.1 kg of resin per m². So the metric defaults are 30 kg of aggregate and 2.0 kg of resin per m², and the US resin default of 0.43 lb/ft² is about 7% of the aggregate.

Use your supplier's figures

These are typical, not universal. Aggregate blends differ in density and grading, and each system has its own resin ratio, so the kit label or data sheet for the product you're buying beats any default. The result card shows the resin share, the resin rate as a percentage of the aggregate rate, so you can check it against the supplier's mix at a glance.

Suppliers also set minimum depths. Ronadeck, for example, asks for at least 15 mm for foot traffic and 18 mm for driveways when mixed with kiln-dried aggregate no larger than 6 mm. SEK's figures follow the same pattern, with deeper layers for heavier use.

How well the depth scaling holds

The calculator assumes material rises in straight proportion to depth, and SEK's own table shows how close that is. At 5/8 in, a kit covering 38.7 ft² is 200 ÷ 38.7 = 5.17 lb of aggregate per ft², and scaling the 3/4 in rate gives 6.2 × 0.625 ÷ 0.75 = 5.17, the same figure. At 1 in, the kit's 23.7 ft² is 8.44 lb per ft² against a scaled 8.27, about 2% apart. That's close enough for planning; for deep, heavy-duty layers, use the supplier's coverage at that exact depth.

Turning the result into kits

Because the materials come in matched kits, the practical order is a number of kits rather than a weight. Divide the area by what one kit covers at your depth and round up. The US default of 430 ft² at 32.3 ft² per kit is 13.3, so 14 ResinScape kits. The metric default of 40 m² at 3.5 m² per BoundWorx kit is 11.4, so 12 kits. The calculator's weights tell you whether a quote's kit count is in the right range; the kit count is what you buy.

The base matters more than the topping

Resin-bound is a thin wearing layer, so it only performs on a firm, stable base: sound concrete or asphalt, or a purpose-made permeable base where the supplier allows it. SEK's sheet gives separate base build-ups for pedestrian, vehicular and light commercial use, and says new concrete should be fully cured, 28 days, before resin goes on. The same sheet gives an installation temperature range of 40 to 85°F (about 4 to 29°C), an initial set of about 3 hours and a full cure of 24 hours at 68°F (20°C). Other systems differ, so follow the data sheet for the product you use.

The installed rate is a separate input because contractor prices vary with region, base condition and access. Enter a quote's price per square foot or metre and the calculator multiplies it by the area. It doesn't add the cost of breaking out an old surface or building a new base.