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Hebden 402 Permeable EcopavingInformation Sheet

Applications: • Car parking • Emergency vehicle access • Temporary and permanent roadways • Quick fit shed bases • Road protection • Embankments • Green roofs • Driveways • Tree beds • Golf walkways • Caravan parking • Equine hard standing

Hebden 402 - The permeable paving solution

Dimensions 33 cm x 33 cm x 4 cm

Wall thickness, Wall height

3 mm, 40 mm

Weight per tile 0.57 kg

Weight per m²: 5.13 kg

Material: 100 % recycled polyolefin

Compressive strength: Up to 16 tonne axle load in accordance with DIN1072

Loadbearing capacity: Up to 320 tonne/m2

Natural stability: Temperature range -50°C up to +90°C

Dimensional changes: Approx. 0.5 % (at a standard temperature +20°C up to 80°C)

Humidity absorption: 0.01 %

Environmental compatibility:

Harmless, groundwater neutral, weatherproof and UV resistant

Solubility: Resistant against acid and leaches, alcohol, oil and petrol (strewing salt, ammonia, acid rain etc.)

Installation: 100 m² per person per hour

Infill Options Include... Gravel, Grass, Soil, Chippings, Turf, Chipped Rubber, Mulch

Hebden 402 is fully compliant with new planning requirements surrounding driveways to the front of properties.

• Environmentally Friendly • Prevents erosion and wear on footpaths • Interference connections creating stronger inter-grid unions • Strengthens grassed areas • Minimal dimensional change due to temperature • Resistant to water, corrosion and cracking • Holds gravel and prevents rutting • Strong geometric design ensures high compression strength

Installation Guide for Hebden 402

There are three methods of laying Hebden 402 dependant on the ground conditions and local authority requirements.

All guidelines here are for use by private cars and light commercial vehicles. For heavier vehicles, depth of the sub base will need to be increased proportionately.

System A. Total infiltration – all water passing through the paved area is to be absorbed into the ground.

System B. Partial infiltration – some of the water will pass into the ground but some will be channelled to drain away elsewhere.

System C. No infiltration – complete capture of the water under the pavement for drainage elsewhere. Ideally application method C is for level ground. Consider how water may flow and accumulate on gently sloping sites. For more significantly sloping sites terraced areas with compartmental walls may be necessary.

There is no need to design falls into the pavements as all rainwater should soak in and drain away naturally.

PLEASE NOTE - MATERIALS USED IN ASSOCIATION WITH HEBDEN 402 AND OTHER PERMEABLE PAVING SYSTEMS DIFFER FROM CONVENTIONAL FLEXIBLE PAVER LAYING.

Hardcore is not ideal for this type of application nor MOT Type1 as it compacts, giving insufficient water storage capability unless additional drainage is used. We recommend MOT Type 3.

Before you begin you will need to seek advice from your local Planning Office as to the most suitable method, for systems B and C drainage into Local Authority water systems may need permission.

Subgrade assessment

The bearing capability of the soil should be established ideally by a CBR (Californian Bearing Ratio) test described in BS 1377-4+A2:2002. This will determine the ability of the ground conditions to transmit load evenly, and indicate the required depth of the sub-base layer. A capping layer may be required to stabilise certain ground conditions. Preparation of the sub-grade and laying should be in accordance with BS 7533-3 however basic guidance follows.

For systems A and B the highest recorded groundwater level should be at least 1 metre below the bottom of the sub base. This allows filtration of pollutants from the driveway and also means the storage capacity of the system is not reduced at times of high groundwater.

Assessment of likely volume

Be mindful of the amount of rainfall that can fall in any given period and if other sources of runoff may affect the storage capacity and drainage potential of your drive, i.e. down-water pipes,other surfaces adjacent to the drive and their level and direction of fall. The amount of increased run-off expected will increase the depth of the coarse graded sub-base to enable it to cope.

Do not construct soak-away close to buildings to prevent damage to foundations.

For driveways sloping towards the house a drainage channel will be needed to direct any excess surface water away.

Cutting

Grids can be cut using a hand or power saw to fit around obstructions and curves. Cut pieces which are less than 50% of original size should be avoided if at all possible.

System A. Total infiltrationLaying pavers where the intention is all water will drain into underlying ground. This method is most suited for free draining soils and may require no additional drainage system.

Laying Guidelines System A

• Excavate to design depth, remove soft spots and make good.• Lay edge restraints where required and allow setting material to harden before commencing laying. (Please

note, some form of edging or kerbing must be place at any point where vehicles will access the pavers.)• Lay optional geo-textile to prevent migration of material into subgrade.• Lay coarse graded sub-base to required depth, use plate vibrator to ensure compaction during and after.• Place another optional geo-textile to prevent smaller layer migrating into coarse material.• Add laying course using a levelling screed, place the pavers whilst working.• Use a plate compactor to level.• Fill in material of suitable sized particles. Where surface will be regularly trafficked, we recommend a blend of

14mm-20mm chippings (to prevent migration in the tread of tyres) slightly over-filled. If the surface is to be grassed, we recommend mixing the grass seed with the soil before filling.

Hebden 402 pavers

Laying course of Class M course sand or crushed fines for gravel, or a compost/sand mix rootzone for grass. Recommended 50mm depth.

Optional geo-textile.

Coarse graded aggregate sub-base.(4/20 or Type 3 sub-base – 4-20mm diameter)Minimum 200mm depth (additional depth may be required for low CBR soils)

Optional geo-textile.

Sub-grade (earth)

System B. Partial infiltrationLaying pavers where the intention is some water will drain into underlying ground and some is channelled away.

This method can be used where the existing ground condition may not be capable of absorbing water quickly.Where the existing sub-grade may not be able to absorb all of the water, a network of drainage pipes are laid on the sub-grade to aid water dispersal.

Laying Guidelines System B

• Excavate to design depth, remove soft spots and make good.• Lay edge restraints where required and allow setting material to harden before commencing laying. (Please note,

some form of edging or kerbing must be place at any point where vehicles will access the pavers.)• Lay optional geo-textile to prevent migration of material into subgrade.• Lay perforated or fin pipe cloaked in geo-textile.• Lay coarse graded sub-base to required depth, use plate vibrator to ensure compaction during and after.• Place another optional geo-membrane to prevent smaller layer migrating into coarse material.• Add laying course using a levelling screed, place the pavers whilst working. Use a plate

compactor to level.• Fill in material of suitable sized particles. Where surface will be regularly trafficked, we recommend a blend of

14mm-20mm chippings (to prevent migration in the tread of tyres) slightly over-filled. If the surface is to be grassed, we recommend mixing the grass seed with the soil before filling.

Hebden 402 pavers

Laying course of Class M course sand or crushed fines for gravel, or a compost/sand mix rootzone for grass. Recommended 50mm depth.

Optional geo-textile.

Coarse graded aggregate sub-base.(4/20 or Type 3 sub-base)Minimum 200mm depth (additional depth may be required for low CBR soils)

Optional geo-textile.Drainage pipes.Sub-grade (earth)

System C. No infiltrationLaying pavers where the intention is to capture all water and channel to suitable drainage or harvesting area.Where the existing sub-grade has low permeability or low strength this system allows total water entrapment and controlled drainage. This system can also be used in conjunction with water harvesting systems.

System C relies on an impermeable membrane lining the excavated area to capture water. It should be laid on the excavated sub-base and the sides brought up to just beneath the paving level.The drainage pipe should extend to at least 1m into the tanked area and be completely wrapped in geo-textile. The inlet hole made in the impermeable membrane must be sealed around the pipe.The outflow is then connected to a suitable harvesting or drainage system.

Laying Guidelines System C

• Excavate to design depth, remove soft spots and make good.• Lay edge restraints where required and allow setting material to harden before commencing laying. (Please

note, some form of edging or kerbing must be place at any point where vehicles will access the pavers.)• Lay optional heavy duty geo-textile protection fleece if concerned about the possibility of ground material

puncturing membrane.• Lay, robust welded waterproof membrane typically 1mm thick polypropylene.• Lay perforated or fin pipe cloaked in geo-textile.• Lay coarse graded sub-base to required depth, use plate vibrator to ensure compaction during and after.• Place another optional geo-membrane to prevent smaller layer migrating into coarse material.• Add laying course using a levelling screed, place the pavers whilst working. Use a plate compactor to level.• Fill in material of suitable sized particles. Where surface will be regularly trafficked, we recommend a blend

of 14mm-20mm chippings (to prevent migration in the tread of tyres) slightly over-filled. If the surface is to be grassed, we recommend mixing the grass seed with the soil before filling.

Hebden 402 pavers

Laying course of Class M course sand or crushed fines for gravel, or a compost/sand mix rootzone for grass. Recommended 50mm depth.

Optional geotextile.

Coarse graded aggregate sub-base.(4/20 or Type 3 sub-base) Minimum 250mm (additional depth may be required for low CBR soils)

Drainage pipes wrapped in geotextile.Impermeable membrane (puncture resistant HDPEor EPDM with welded joints).Optional fleece geotextile.Sub-grade (earth) – may need stabilising with acapping layer.

Clarification of terminology

Subgrade – upper part of the soil, natural or constructed, that supports the loads transmitted by the overlying pavement.Capping layer – layer of material placed on the subgrade to stabilise its performance under load if required.Sub-base – one or more layers of open graded material placed immediately above the subgrade.Coarse graded aggregate – main structural and hydraulic functional layer with particle size within therange of 20 to 4mm to BS 12620.Laying course – layer of material on which pavers are bedded. Typical particle size 2 - 6.5 mm.Geotextile – permeable textile, mesh, net or grid that allows water to flow through and prevents migrationof particulates between construction layers.Impermeable membrane – membrane which is intended to contain all water entering the pavementcontrolling its flow

The table below showing sub-base thicknesses is intended as a general guide in accordance with BS7533. For further details on permeable paving design refer to BS7533 Part 13; for installation refer to BS7533 Part 3.The design for pavements should satisfy two parts - to support the traffic load and to manage the surface water effectively.

The strength of a subgrade is measured by California Bearing Ratio (CBR). The design CBR should be obtained either by testing or by measurement of the plasticity index of the subgrade material. In the case of CBR testing, the method described in BS1377-4:1990+A2:2002, Clause 7 should be used.The surface of the subgrade material should be prepared according to the Highways Agency’s Specification for Highway Works, Clause 616.

Detailed preparation of the subgrade should be in accordance with the recommendations in BS7533-3.

Additional products

Delineators

One of the trickiest aspects of having a gravel parking area that is used by several vehicles is getting people to make the best use of the space and to park tidily.

This is where our delineation system for the Hebden 402 comes in handy.

The highly visible white "mushroom" plugs are firmly pushed into the sockets of the Hebden 402 grids but, once inserted, they are very hard to remove making them highly resistant to passing vandals.

Stakes

When laying out Hebden 402 grids on any slope greater than 5%, or 1 in 20, it is essential that the row of grids at the highest point is staked down. It is also desirable that a few other grids are staked down along the edges on larger areas that are sloping.

Currently, we do not supply stakes. The example below is a perfectly economical and effective option and is available from B&Q at the time of making this information sheet. B&Q list it as a log roll stake, but generic, galvanised stakes are widely available. This particular example is made by Gardman and measures 460x36mm.