Test to determine the permeability of the ground. Dig a hole in the area to be paved approximately 600 x 600mm and deep enough to clear the topsoil, leaving the sub-soil exposed. In this sub-soil, dig a further hole 300x300x300mm and fill with water. If the hole empties within 24 hours then the ground is probably suitable for a SuDSFLOW driveway.
Use a no-fines self-locking aggregate either 4-1mm or 5-6mm hard clean crushed stone.
2-6mm clean hard crushed stone (angular, no-fines). Depth 30-50mm.
No-fines coarse graded aggregate (CGA) clean crushed stone 4-20mm or 4-40mm aka Type 3 material (30% voids) Depth 180-300mm.
These can be used in 0-3 places in the substrate – in particular consider a geo-textile between the sub- base and bedding course. However provided there is adequate interlock between the aggregate particles – geo-textiles can be an unnecessary cost imposition.
SuDSFLOW provides an environmentally friendly alternative to porous paving for pavements, driveways, carparks etc for both the domestic and commercial markets. It is the Resigap Ltd stated intention for SuDSFLOW to become one of the best validated SuDs paving systems and as such strives to comply with the requirements for the Code for Sustainable Homes, BREEAM, the EU Water Framework Directive and the DEFRA Future Water document.
The use of SuDSFLOW spacers in combination with suitable paving units and bedding materials should address water management, pollution removal and rainwater recycling issues, thereby providing a sustainable drainage system.
SuDSFLOW spacer permeable modular pavement systems allows rainwater to directly infiltrate into the subgrade. SuDSFLOW can also however be used as part of a Tanked System allowing rainwater to attenuate before release; additionally the same system can be useful where difficult or contaminated sub-grades are encountered.
Construction costs incorporating SuDSFLOW spacers to create a SuDS drainage system can be less expensive than conventionally drained surfaces as it is not necessary to incorporate gullies, drainage pipes, drain runs and flow control mechanisms required for conventional drainage. Additionally our suggested sub-base (1.8 tonnes/m3) is open textured and therefore has a greater spread rate than traditional Type 1 (2.2 tonnes/m3). Specialist permeable paving units (i.e. Marshalls Priora) are not required, potentially adding further to the cost savings.
For rainfall occurrences with minimal rainfall depths (<5mm) there should be no effective run-off from a SuDSFLOW pavement. Run-off during heavy periods of rain is virtually eliminated. A design incorporating SuDSFLOW spacers allow water to infiltrate through vertical channels within the pavement at a rate of up to 10,000mm/m2/hour. Further the compacted sub-base has voids of around 30% of volume which will allow storm water to be attenuated within the system and released in a controlled manner over a period of time.
On porous ground, and where there is adjacent flower beds and/or lawns consideration should be given to leave gaps at suitable intervals along the haunching to allow the bedding course to additionally drain into those garden areas.
If there is cause for concern that standing water will soften the sub-base in an unlined system, a nominal fall to an outfall should be considered.
Occasionally if the sub-base is silty or plastic it may be necessary to stabilize it or partially replace it with a granular capping.
The total depth of the sub-base may be dictated by the expected loading/desired water storage/sub base strength.
The amount of water which can pass through a permeable flagged pavement is dependent on the infiltration rates of the joint filing, laying course and permeable sub-base materials and not the proportion of open area in relation to the flagged surface.
SHW clause 805 4/40mm (crushed concrete) bound with 2/6 3mm crushed concrete aggregate to EN12620. Graded crushed concrete to EN12620 (re-cycled materials will add significantly to the overall sustainability of the project).
PLEASE NOTE: Because rainwater will pass through the driveway (rather than drained off of it) and the environmental nature of construction in general occasional settlement should be expected and paving can be lifted to simply repair.
It is not feasible for SuDSFLOW spacers to provide a structure which will withstand the greatest rainfall that has ever occurred. It is therefore more economic to tolerate periodic flooding rather than to design a system for every intense storm.
If in doubt re sub-base consult the Interpave ‘Permeable Pavements Manual’.
SuDSFLOW is protected by GB Patent no.1104484.9