Citygrid is designed for heavy duty applications and fully compliant to SuDS (sustainable urban drainage systems). Extensively tested and proven, citygrid will:
– Minimize surface water run off
– Reduce flood risk
– Improve water quality
– Encourage biodiversity
Material: 100% recycled polyolefins
Nominal size: (L x W x H) 60 x 40 x 8 cm / 24″ x 15.75″ x 3.15″
Unit weight: 9 kg / 19.8 lb (37,5 kg / 82.67 lb per 1 m² panel)
Coverage: 4.17 grids/m² or 0.39 grids/ft2 (1 grid = 0.24 m² / 2.58 ft²)
Connection type: Tongue and groove
Infiltration rate: 2,500 mm/hr for gravel
» High compressive strength
» Flexible and resistant to cracking
» Anti-slip & UV resistant
» Harmless to the environment
» Meet SLW60 loading category (vehicle up to 60 metric tonnes / 66 tons gross weight)
» Within HSE manual handling guidelines
Heavy duty permeable ground grid infiltration
1. Grass seeded or gravel finish
2. Citygrid units (permeable grid)
Grass: Good quality, free-draining friable topsoil, seeded at 6 -10 lbs per 1,000 ft² or 35–50 g/m², pre-seeding fertilizer applied.
Gravel: Clean, free-draining angular crushed rock 0.2 – 0.6″ or 5–15 mm. Do not use rounded or river washed gravel.
3. Grit bedding
Clean coarse 0.08 – 0.25″ or 2–6 mm grit compacted to 0.8″or 20 mm.
4. Geotextile filtration layer
Non-woven needle-punched, minimum 3.25 oz/yd² or 100 g/m2.
5. Free-draining engineered sub-base
Free-draining granular base with a depth to suit the anticipated loading. N.B. Standard granular base is not suitable as it’s not free-draining.
6. Geotextile separation layer/Geogrid
30/30 geogrid on a non-woven needle-punched geotextile, minimum 3.25 oz/yd² or 100 g/m².
7. Sub soil
Establish CBR value to calculate depth of free-draining granular base.
» Installation Instructions
1. Excavate and prepare the area. Install any curb or edge restraint and lay the geotextile separation layer with the geogrid on top (for attenuated areas, add a sealed geomembrane beneath). Add the engineered free-draining stone base layer to the recommended depth and compact.
2. Install a second separation geotextile layer, lay and compact the grit bedding and screed to level.
3. Lay the first permeable grid units along a straight edge or curb, if against a curb leave a 1” or 25 mm expansion gap. Work to string lines, in a similar way to laying block paving. Work across the site in rows, making sure that the tongue and groove fits together. The grids can be laid in either orientation and staggered bond, if required.
4. Permeable grid units can be cut to size with a standard stone cutter, but avoid cutting pieces to less than 1/3 of a unit.
5. Grass finish: Fill the grids with good quality friable topsoil and sweep off any excess. Use a vibrating plate to bed the units in and settle the topsoil to just below the grid top. Sow the grass seed mix at 6–10 lbs per 1,000 ft² or 35–50 g/m² and apply a good quality fertilizer. Water the area regularly in the initial growing period and, ideally, wait until the second cut of the grass before vehicular use.
Gravel finish: Fill the grid cells with angular ¼ – ¾” or 5–15 mm gravel (rounded gravel is NOT recommended). Use a vibrating plate to bed the units in and settle the fill. Top the gravel up so that it is level with the grid. Vehicles can use the area as soon as the grids have been filled.
6. Routine maintenance, weeding and debris clearing will prevent any reduction in the porosity of an area paved with permeable grid. For specialist maintenance such as snow clearing:
a. Use a rubber-edged plow OR a metal edged snow blade at least 1” or 25 mm off the surface.
b. Take extra care in extreme cold conditions due to frozen grass. Check the surface when thawed and repair as required.
» Quantity calculations
Bedding grit: 820 lbs per 100 ft² or 1 tonne per 25m²
Gravel infill: 1,430 lbs per 100 ft² or 1.8 tonnes per 25m²
Topsoil infill: 1,270 lbs per 100 ft² or 1.6 tonnes per 25m²
» Laying rates
A three-person team can lay up to 3,230 ft² or 300 m² per day.
Permeable grid should be installed with a 1/32” – 1/16” or 1-2 mm gap between units. This allows the tongue and groove to fit while accommodating a 70–90°F (25–30°C) temperature change. For larger areas, a 1” or 25 mm gap (filled with gravel/topsoil) should be left between any hard edge or curb.
» Installation on gradients
The maximum gradient for vehicle use is 8% (1 in 12).
|citygrid Permeable Paver installation in grass||dwg|
|citygrid Permeable Paver installation in gravel||dwg|
» Tried & Tested
Porous paving is increasingly used in North America and worldwide for access, parking lots, truck parking and bus terminals. The first porous paving systems were made of concrete, but concrete has weight, flexibility and durability limitations. This is why grids made of 100% recycled plastic are so effective.
As well as environmental benefits and the ability to take very high dynamic loads, Heavy Duty Permeable Ground Grid flexes under pressure rather than breaking like equivalent concrete products. Heavy Duty Permeable Ground Grid is not plagued by frost damage (unlike concrete), is lightweight by comparison and very robust when handled. Heavy Duty Permeable Ground Grid doesn’t crack if dropped, it can be carried/installed by a single person and complies with manual handling guidelines.
» Strength testing
The most common testing for heavy duty loads is SLW60. Although useful, these tests only prove if a grid can bear the static load of a multi-axle 66 ton truck. Most plastic grid systems meet this standard.
As well as meeting SLW60/HS-25 requirements, unlike most competitors, citygrid (Heavy Duty Permeable Ground Grid) has been extensively tested to DIN EN ISO Standards for:
» Bending stress at 41°/73°/149°F (5°/23°/65°C)
» Timed bending stress at 1, 24 and 100 hours
» Tensile strength (ultimate and timed)
» Compressive strength at 1, 2, 10 and 20% deflection
» Charpy impact resistance
» Shore hardness (impact)
» Ball striking hardness
» Density, water absorption, thermal expansion and screw pull-out strength
Standard concrete units have a flexural strength of at least 725 psi or 5,000 kN/m². Heavy Duty Permeable Ground Grid achieves 2,200 psi or 15,200 kN/m² so it can flex under pressure instead of cracking. Typical trucks exert a static tire load of around 120 psi or 833 kN/m². The Heavy Duty Permeable Ground Grid crushing strength of 2,600 psi or 18,000 kN/m² means it bears virtually any load.