Paving to domestic front gardens and driveways.
Paving to all commercial scenarios.
The objective here is to reduce flood risk and mitigate the effect of years of paving over what were naturally green areas with non-permeable surfaces.
You don’t need planning permission to build or replace a driveway of any size if:
- you use permeable (or porous) surfacing, e.g. gravel, permeable concrete block paving or porous asphalt
- the rainwater flows to a lawn or border to drain naturally.
If you cover more than five square metres using traditional materials that don’t let water through, you need planning permission.
These rules apply to the area of land between the front walls of the house and the highway. This is classed as in curtilage.
surfacing is not acceptable/deemed permeable in the following scenarios:
- Over-lays to existing concrete or Tarmacadam surfacing even if the concrete/Tarmacadam has been drilled or altered in any way to make it ‘permeable’ unless the existing concrete did not fall to roadways or to existing house drains. Such alteration is prone to clogging with surface detritus.
- Any surfacing falls to existing gulley points around the house
- Any surfacing is found to fall to roadways or outside of the property.
Surfacing is not deemed permeable:
- If any of the surface courses are not deemed permeable such as type 1 with a high fines content sub-base, open grade tarmacadam with too high a tar content which would inhibit permeability.
Infiltration and attenuation
Surface water can be directed away from traditional drainage points or falls to roadways by the use of attenuation systems, rainwater harvesting systems or infiltration systems.
Known as soakaways in the past, usually formed from excavating a pit and filling with clean stone. Problem is that the void ratio was only 30%. Modern systems are formed with the use of crated soakaways wrapped with a geotextile fabric towards which surface falls are directed. Surface water enters the infiltration system via falls or channel drains and fills the system. Water dissipates over a non-specific period of time.
This is similar to an infiltration system but the crate is wrapped with a non-permeable membrane. Flow out of the system is regulated by a flow control such as a vortex flow control device. E.G 30 litres per second.
A system that consists of an underground or above ground tank. Rainwater is still attenuated but can also be used for various uses around the house such as garden watering, car washing, toilet flushing.