Acceptable Materials
The type of permeable surfaces that are acceptable include Gravel, permeable Block Paving, and porous concrete and asphalt. Driveways built before October 2008 do not have to gain planning permission retrospectively.There are also other issues for preventing gardens being turned into driveways, such as the destruction of microclimates where insects and grubs can survive that in turn are food for small animals and birds, and the fact that hard surfaces reflect the heat of the sun rather than absorb it.
You will not need planning permission if:
- a new or replacement driveway of any size uses permeable (or porous) surfacing, such as gravel, permeable concrete block paving orporous asphalt
- or if the rainwater is directed to a lawn or border to drain naturally.
You will need Planning Permission if:
You are laying a traditional, impermeable driveway that does not provide for the water to run to a permeable area where the surface to be covered is more than five square metres.
Problems with Patios and Driveway
in 2007 serious floods struck the UK. This resulted in loss of life, disruption of peoples lives and caused damage estimated at about £3bn. In many cases the flooding happened because drains could not cope with the amount of rain water flowing to them. The effects of climate change mean that this kind of heavy rainfall event and subsequent flooding may occur more often in the future.
The drains in most urban areas were built many years ago and were not designed to copewith increased rainfall. Paving front gardens further adds to the problem. Although paving over one or two gardens may not seem to make a difference, the combined effect of lots ofpeople in a street or area doing this can increase the risk of flooding.
The harm caused by paving gardens is not limited to just flooding. Hard surfaces such as concrete and asphalt collect pollution (oil, petrol, brake dust etc) that is washed off in to the drains. Many drains carry rainwater directly to streams or rivers where the pollution damages wildlife and the wider environment. In older areas the rainwater may go into the foul water sewer which normally takes household waste from bathrooms and kitchens to the sewage treatment works. These overflow into streams and rivers in heavy rainfall. As more water runs into foul sewers from paved areas there are more frequent overflows, passing untreated sewage into watercourses.
Replacing grass and plant beds with concrete and asphalt surfaces means that water does not soak into the ground. This reduces the amount that reaches our natural underground aquifers. Some water that soaks into the ground will evaporate back into the air, causing acooling effect around the house. This is lost if the garden is covered with hard impermeable surfaces and can cause local temperatures to rise often referred to as the urban heat island effect.
Solving the Problems
You can provide paved areas in front of your house without adding to flood risk and pollution. You can use permeable surfaces that allow water to drain into them or by other methods such as rain gardens
Permeable driveways are often more attractivethan an expanse of concrete, adding value to the property. These types of surfaces canalso be better for the environment and do not necessarily cost more or require a lot of maintenance.
There are three main types of solution to creating a permeable driveway:
• Using gravel or a mainly green, vegetated area.
• Directing water from an impermeable surface to a border rain garden or soakaway.
• Using permeable block paving, porous asphalt or concrete.
The most appropriate construction will depend on factors such as the space available, slopes, the type of soil and whether the existing garden gets waterlogged.
You can also combine the methods in a single garden to get an interesting appearance
How do they work?
Modern permeable surfaces work by allowing water to soak through the surface into the ground below. Soakaways can be located along the edges of impermeable driveways or inthe garden area to collect water and allow it to soak into the ground. On clay soils it may be necessary to connect to the house roof water drain.
The materials used in permeable construction are different to those used in impermeable driveway construction. Both types of surface have a sub-base layer used to make theground strong enough to carry cars without rutting.Conventionally surfaced driveways use a sub-base material called hardcore or a material called MOT Type 1 by contractors.
3 Options
Water from a paved surface can be dealt with using three main approaches:
• Soaking into ground (soakaway)
• Rainwater harvesting or storage for later use
• Flowing to the drains, but this should be the last option considered and might not bepermitted development
A combination of systems can also be used, where water soaks into the ground but there is also an overflow connection to the drains for periods of really heavy and extended rainfall. This is useful if the soils are clay and do not drain very well. Rainwater harvesting systems will usually have an overflow to a soakaway or drain.
Where the new driveway is small, if the existing garden is not water logged it should be acceptable to allow the water to soak into the ground. If the garden is already waterlogged the sub-base below the driveway will need to be drained by connecting a pipe from within the sub-base to the drains.
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