Technical specification
How resin bound surfacing is properly laid.
The depths, aggregate grades, resin ratios, weather windows and cure times we work to on every job. If a quote you have been given does not state these numbers, ask why.
Laying depths
Depth by application
| Application | Finished depth | Aggregate grade | Notes |
|---|---|---|---|
| Footpaths & garden paths | 15 mm | 1–3 mm | Pedestrian only. Minimum practical depth for a stable, permeable finish. |
| Domestic paths & patios | 18 mm | 2–5 mm | Our standard for cars and light vans up to 3.5 t. |
| Patios & courtyards | 15–18 mm | 1–3 mm or 2–5 mm | Depth follows the base type and any level constraints at thresholds. |
| Commercial / light HGV | 20–24 mm | 2–5 mm (occasionally 3–6 mm) | Laid over a reinforced or thicker bituminous base, designed per traffic loading. |
Rule of thumb: the finished depth should be at least three times the largest stone size. A 2–5 mm aggregate therefore cannot be laid below 15 mm.
Weather window
Temperature & moisture limits
Resin is a chemical cure, not a drying process. Scottish conditions mean the laying window matters more here than almost anywhere else in the UK — we will postpone a job rather than lay outside these limits.
Minimum air temperature
10 °C
and rising — we do not start below this.
Minimum surface temperature
5 °C
measured on the base, at least 3 °C above dew point.
Maximum working temperature
25 °C
above this the pot life shortens sharply; we work early morning.
Relative humidity
Below 80%
high humidity slows cure and can cloud the resin.
Rain
Dry for 24 h after
no laying in rain, and no rain forecast during the initial cure.
Base moisture content
Below 2.5%
the base must be visibly dry — no standing water or damp patches.
Practical season: in the west of Scotland that usually means March to early November. Winter installations are possible with a winter-grade hardener, tented working and a heated, dry base — we will tell you honestly if the conditions do not suit.
Materials
Resin & mix ratios
- Resin system
- Two-part UV-stable aliphatic polyurethane (clear, non-yellowing)
- Standard mix
- 7.5 kg resin (Part A + Part B) to 125 kg kiln-dried aggregate
- Mixing time
- Minimum 2 minutes forced-action mixing until every stone is coated
- Pot life
- Approx. 20 minutes at 15 °C — less in warm weather, more in cold
- Aggregate
- Kiln-dried, washed, moisture content below 0.5%
- Coverage
- One 125 kg mix covers roughly 6.5 m² at 18 mm
Cure times
When you can use it
Times quoted at 15 °C. Every 10 °C drop roughly doubles them; below 10 °C the cure may stall altogether.
Build-up
The full construction, layer by layer
1. Excavation
Dig out 150–200 mm for a domestic path or patio (more on soft or clay ground), to a firm, uniform formation. Existing tarmac or concrete in sound condition can be retained as the base.
2. Sub-base
100–150 mm of MOT Type 1, or clean 20 mm angular stone / Type 3 where full permeability and SuDS compliance is required. Compacted in layers of no more than 75 mm with a vibrating plate or roller.
3. Edge restraints
Concrete-haunched kerbs, block edging, aluminium or steel edging installed before the base course so the finished surface is fully contained.
4. Binder course
50–65 mm of open-graded porous asphalt for permeable builds, or 60 mm AC20 binder plus 20 mm AC6 surface course for standard builds. Concrete bases require expansion joints to be carried through and a minimum 28-day cure.
5. Falls & drainage
Impermeable bases are laid to a minimum 1:80 fall away from the building, with channel drainage at thresholds. Fully permeable builds discharge through the sub-base, subject to soil infiltration testing.
6. Priming
Fresh asphalt is left 7–14 days before priming. Concrete, damp-prone or non-porous bases get a dedicated primer or damp-proof membrane, applied and allowed to tack off before resin is laid.
7. Laying & trowelling
Mixed material is placed and screeded to the design depth, then hand-trowelled with a smoother tool and a little denatured alcohol to close the surface. Wet edges are kept live so joints disappear.
8. Cure & handover
The surface is barriered off, checked for depth and finish once cured, and handed over with an aftercare sheet and written guarantee.
Quality control
What goes wrong, and why
Laying below 5 °C surface temperature
Resin never fully cures — soft, sticky or crumbling surface.
Damp base or aggregate
Foaming, blistering and loss of bond between resin and stone.
Under-mixing
Dry, unbound stone that ravels out within weeks.
Laying too thin over a rough base
Telegraphing, cracking and premature failure.
Skipping edge restraints
Edges break away as soon as a wheel runs over them.
Aftercare
Looking after the surface
- ✓Keep off completely for the first 24 hours; no vehicles for 48 hours.
- ✓No turning the steering wheel while stationary — it scuffs any resin surface.
- ✓Brush or blow leaves off regularly and rinse with a hose; a pressure washer under 150 bar, fan tip, held 300 mm back is fine.
- ✓Treat moss and algae twice a year with a proprietary resin-safe cleaner.
- ✓Never use rock salt for ice — use a plastic shovel and grit-free de-icer.
- ✓Keep the permeable surface clear of silt so infiltration rates stay high.
Want this spec on your project?
Free site survey, written quotation and a clear method statement before any work starts.