A car park is paved once and rained on every monsoon. Most are built in asphalt, paver blocks or concrete, with surface drains to carry the water away. GridMats S2 takes a different route: clean stone chips locked in a recycled-polypropylene grid on an open-graded base, so the rain is managed below the surface.
We ran one car park through the GridMats Design Engine to see what that costs against the usual choices.
The car park
- 2,000 m² (about 21,500 sq ft) of parking
- Cars, SUVs and light vans up to 3.5 t, 100 a day; soil CBR 5%
- Moderate rainfall (750–1,500 mm a year); Hyderabad rates, ex-GST
Four sections for the same cars
- GridMats S2, 215 mm in all. OC-LW 40 filled with 8–12 mm angular chips and plate-compacted flush, on 25 mm of crusher-dust bedding and 150 mm of open-graded GSB that stores the rain, over a non-woven geotextile separation layer, with perforated pipes along the low edges to the outfalls.
- Asphalt, 325 mm. A 25 mm premix carpet on 150 mm of WMM and 150 mm of GSB, with a lined surface drain.
- Concrete paver blocks, 240 mm. 60 mm pavers on 30 mm of bedding sand and 150 mm of GSB, with a lined surface drain.
- Concrete slab, 300 mm. 150 mm of PQC with dowels, tie bars and saw-cut joints on 150 mm of GSB, with a lined surface drain.
All four have kerbs on both sides.
What it costs
| Section | To build | Over 35 years, in today's money |
|---|---|---|
| GridMats S2 | ₹127 per sq ft (₹1,364 per m²) ₹27.3 L for the car park | ₹157 per sq ft (₹1,695 per m²) ₹33.9 L for the car park |
| Asphalt | ₹90 per sq ft (₹971 per m²) ₹19.4 L | ₹156 per sq ft (₹1,674 per m²) ₹33.5 L |
| Concrete paver blocks | ₹88 per sq ft (₹950 per m²) ₹19.0 L | ₹113 per sq ft (₹1,219 per m²) ₹24.4 L |
| Concrete slab | ₹201 per sq ft (₹2,166 per m²) ₹43.3 L | ₹233 per sq ft (₹2,510 per m²) ₹50.2 L |
The geotextile separation layer under the base is a separate BoQ item and is not included in the GridMats figures above.
What the numbers say
- Paver blocks and asphalt cost less to build for a car park like this: about ₹88–90 per sq ft against ₹127 for S2.
- Over 35 years, S2 and asphalt come out level, at ₹157 and ₹156 per sq ft, because asphalt needs a mill and overlay at 12 and 24 years. Paver blocks stay the lowest.
- Against a concrete slab, S2 costs 37% less to build and 32% less over 35 years.
So S2 is not the cheapest car park you can build. It is the one to choose when the points below matter on your site.
When S2 is worth it
- Rain. In this design the open-graded base stores about 59 mm of rain and releases it through the perforated pipes along the low edges. Edge and outfall drains go in only where the levels need them.
- Green-cover and permeable-area rules. S2 supports green-cover rules and permeable-area requirements, subject to local approvals.
- Opening the same day. Nothing to cure: the crew leaves and the cars arrive.
- No cement and no saw-cut joints. About 8 t of recycled polypropylene is put to use in the grid (Design Engine estimate for this car park).
- A natural stone finish in grey, black basalt, white marble or red laterite chips.
- Repairs are a top-up. The cells control migration of the chips and reduce rutting.
How we worked out 35 years
As in our truck-yard comparison, we follow the US Federal Highway Administration's practice for life-cycle cost: a 35-year period, a 4% real discount rate, and credit for the service life left at the end.
- Asphalt: mill and 40 mm overlay at 12 and 24 years.
- Paver blocks: 20% of the blocks relaid every 10 years.
- Concrete: joints resealed every 10 years, with diamond grinding and slab repairs at 20 years.
- S2: a stone-chip top-up every 8 years. This is our planning assumption.
- Routine upkeep each year, as a share of the build cost: 0.5% for concrete, 1% for S2 and asphalt, 1.2% for paver blocks.
At an 8% real rate: S2 ₹146 per sq ft (₹1,567 per m²), asphalt ₹128 (₹1,373), paver blocks ₹104 (₹1,115) and concrete ₹220 (₹2,368).
Other GridMats options
- Grass instead of chips. S3 on the 30 mm grass paver came out at ₹118 per sq ft (₹1,270 per m²) to build in the same run, and ₹184 per sq ft (₹1,982 per m²) over 35 years, because a lawn needs more upkeep. Cars use it once the grass has rooted, in 4–6 weeks.
- Steep ground. On grades steeper than 6%, loose chips can migrate: S1 cement-treated gravel is the better choice.
- A sealed surface. If the car park must be swept clean, choose a sealed finish instead.
Your car park will differ
These are indicative figures for one typical car park. Soil, traffic, rainfall, local rates, freight and the base design change them, and every GridMats site is priced from its own design. Ask for your free estimate: our engineers follow with the design, the bill of quantities and the cost comparison against your conventional section.