way. Of course, a small area of paving in isolation is not going to cause major flooding but the cumulative impact of lots of gardens being sealed up creates real problems. For example, the area of paving over front gardens for car parking that has already occurred in London is estimated as equivalent to around 5,200 football pitches. Just imagine the rainwa- ter runoff in a storm from impermeable paving that big. It is now well recognised that Sustainable Drainage Systems (or SuDS) must play a central role in curbing flooding and pollution from rain- water runoff. SuDS manage surface water by slowing it down and cleaning it up by filtering, and storing it temporarily. SuDS aim to replicate, as closely as possible, the natural drainage from a site before any work took place. Concrete block permeable paving is one of
the most important SuDS techniques. There is a growing choice of concrete blocks available, designed specifically for permeable paving. Essentially they have the same impressive per- formance as conventional precast concrete paving products, being slip resistant, durable, strong and sustainable. And today there are more shapes, styles, finishes and colours than ever to give you real freedom of choice.
Permeable paving
The difference with permeable paving is its enlarged joints, filled with a permeable aggre- gate specifically chosen for each product – but never sand (which is used with conventional block paving). This ensures that water will con- tinue to pass through the joints over many years. The aggregates used below the blocks are also specifically selected to accommodate water, unlike conventional drive and road construction. Water can simply infiltrate into the ground if it is suitable or collected in pipes for gradual dis- charge after the storm. Alternatively, it can be stored for irrigation, washing cars, etc.
Permeable paving is specifically designed for
a dual role, acting as the drainage system as well as supporting vehicles. And it can be used to manage water from roofs as well. At the same time, many pollutants are substantially removed and treated within the paving layers before the water leaves it. Concrete block per- meable paving can be laid level and still avoids puddles without the need for drainage gulleys and pipes. It also provides a safe, firm surface for everyone, including wheelchair users and people pushing prams.
The area of paving over front gardens for car parking that has already
occurred in London is estimated as equivalent to around 5,200 football pitches
Government requirements
fight against flooding. Before the changes, paving anywhere in a
New government requirements for SuDS on developments in England came into force in 2015 and are being implemented through local policies and plans, as well as planning appli- cation decisions on developments of 10 or more dwellings. However, local authorities are increasingly encouraging SuDS on smaller schemes as well, including single homes. In any event, changes in Permitted Development rules have been in place for some time to encourage permeable solutions for new or replacement paving around existing buildings, as part of the
garden related to a house or bungalow with any materials was considered to be ‘permitted development’ – effectively, automatic permission without needing a planning application. However, permitted development rights have been taken away from new or replacement drives or other hard surfaces, unless permeable paving is used or water drains onto a perme- able area within the property. Otherwise, planning permission will be required and this could well be resisted on policy grounds.
Evidence of compliance
These measures took effect in October 2008 in England and Wales to paving over 5m2 (although just for replacement paving in Wales) and in the front garden only. For Scotland, sim- ilar measures apply to areas of any size between the house and any street – therefore not just front gardens. Local authorities may ask homeowners for evidence of compliance.
Enq. 175
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selfbuilder & homemaker
www.sbhonline.co.uk
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