Do driveways cause flooding? It was a question the RHS asked back in 2005 when it was realised that, on average, a quarter of front gardens have been significantly paved over. Since then, heavy rain events have shown that paving over gardens is a major factor in causing severe flooding. In 2007 alone, the associated damage from flooding was £3billion.
As a result, a law was introduced that requires all new drives over five square metres to have planning permission – unless they are constructed using a water-permeable material. So here is our guide on how to reduce paving and which permeable materials to use.
Gardens can soak up rain, while paving, tarmac and concrete are less porous and increase the amount of rainwater that runs off by as much as 50 percent. This additional water usually flows into street drains, which can’t always cope with the thousands of extra litres in a storm. The excess can then go back up people’s front drives to floods their homes. The water has to go somewhere and, even if you are not flooded, it might be affecting your neighbours downhill.
Where is not possible to keep garden space: keep paving to an absolute minimum and use a permeable paving material.
The benefits of permeable paving include:
- Reduce local flooding
- Prevents problems with subsidence. Paving reduces or stops rainfall getting into the ground. This can cause the soil to shrink, especially if it is predominantly clay, which has consequences for structures built on it. Garden walls, paths and houses may develop severe cracks
Additional benefits of not paving over front gardens or keeping the paving to a minimum:
- Leafy streets carry premium prices
- Attractive front gardens have benefits for people too. They provide screening and privacy, creating a green oasis for enjoyment
- If vegetation is lost from our streets there is less to regulate urban temperatures. Hard surfaces absorb heat in the day and release it at night, making it hot and difficult to sleep. This is part of the ‘heat island effect’, which can also be responsible for poorer air quality and localised weather conditions, such as thunderstorms
- Tending your garden at the front of the house gives neighbours the opportunity to meet and can help to build community spirit
- In addition, the research of Ealing Front Gardens Project offers 43 reasons not to pave
Planning and design
Getting a parking space into the front garden and managing to keep some greenery can seem tricky, so here are some simple design solutions for gardens large or small.
If you need to park outside your house, the most logical solution is to pave over the garden. This is certainly a practical option, but with a bit of imagination you can combine paving with an attractive and welcoming garden. And by using materials that allow rainwater to penetrate the ground below, the hard surfaces you do install will shed less water that could otherwise contribute to flooding.
Begin by taking a close look at your front garden. How many cars do you really need to park and how much space do they take up? Have you got walls and fences that climbers could scramble up? Are there dead spaces that could accommodate plants, such as the corners? With the answers to these questions, you can create a design that minimises paving and maximises planting and permeable surfaces. To show how this works in practice, look at the following three examples. The ideas can be used in just about any front garden.
The terraced house is a familiar feature of many of our towns and cities, but its front garden is small and needs careful planning to maximise space. To keep the hard surfaces to a minimum, create just two paved tracks to take the car wheels. The rest of the area can be covered with permeable plastic membrane to suppress weeds, then topped with gravel. By simply cutting through the membrane, you can then grow plants that will spill over the gravel.
Gardens of semi-detached properties are generally large enough for several cars. In this illustration space has been created for two cars, one of which is only parked on the drive at night and weekends. The main parking space is in front of the door, while the second space is off to the left. The hedge will filter some of the dust from the street and there are berries for birds and nectar for butterflies.
The frontages of town houses vary greatly in size, but this larger property has enough room to accommodate three cars unobtrusively. The first vehicle sweeps to the right and parks alongside the existing wall. Behind, a new hedge helps screen it and prevents it being seen from the main rooms on the ground floor. The second car fits on the pavers to the left, while a third car can occasionally be parked on the adjacent lawn, which has been reinforced with a plastic mesh.
Types of permeable paving
If you do choose to pave, go for permeable products that allow rainwater into the ground below. Here are just some of the materials available. However, do visit your local builders’ merchants or DIY store as you may find more options.
Gravel is by far the cheapest permeable hard-landscaping option. It comes in many colours, depending on where it was quarried, and can be bought in bags or by the tonne. You can also buy recycled products, such as Eco Aggs’s gravel which is a by-product of the ceramics industry.
Cost: Gravel and aggregate prices start at just £3.75 per sq m (inc delivery), and locally quarried materials are usually the most inexpensive.
These bricks have the appearance of traditional block paving, but their interlocking shape ensures rainwater can penetrate the tiny gaps. They need to be installed correctly on to compacted aggregate so the water can drain away freely.
Cost: Priora pavers are available from Marshalls and cost from £16 per sq m. Aquaflow Permeable Paving is available from Formpave, from £18 per sq m.
This compares favourably with products of similar quality, such as Marshalls Tegula Pavers which cost about £16.50 per sq m.
Also known as cellular paving, these hexagonal cells are made from recycled plastic and hold an aggregate of your choice, such as resin-bonded gravel. They usually come in green, although other shades are available. Just lay them according to the manufacturers’ instructions, so that rainwater drains away thoroughly.
Cost: Try Addastone Matrix Paving, which are priced from £60 per sq m (DIY) or £100 (installed).
There is a range of products that can be used to reinforce grass. These make the surface suitable for driving vehicles over and prevent it turning into a muddy field. Grassguard from Marshalls is made from concrete (above), but there are tough plastic versions too, such as Netpave from Netlon.
Cost: Grassguard £22 per sq m; Netpave £16.50 per sq m (including delivery).
PLEASE NOTE: the prices are an approximate guide and may vary from area to area and between products.
Communities and Local Government: Understanding permeable and impermeable surfaces
Suitable plants for under cars
If the car is moved fairly regularly, then there are plants you can grow that will tolerate being parked over. These need to be low-growing so the car does not brush them, and tough enough to withstand the occasional running over. Try creeping jenny (Lysimachia nummularia), bugle (Ajuga reptans) and thymes such as Thymus serpyllum. Just leave planting pockets in the paving or gravel to ensure there is soil for them to grow in, rather than hardcore or a bed of concrete.
For more ideas, see pp10-11 of the RHS Front Gardens booklet.
Paving and the law
- If you use permeable paving, you will not need planning permission for a new or replacement driveway
- If the surface is to be covered with more than five square metres of an impermeable material, planning permission will be needed for the driveway. This means a planning application to be made to your local council, and there is usually a fee payable (typically around £150)
- In some areas of the country, known generally as ‘designated areas’, permitted development rights are more restricted. If you live in a Conservation Area, a World Heritage Site, a National Park, an Area of Outstanding Natural Beauty or the Norfolk or Suffolk Broads, you will need to apply for planning permission for certain types of work which do not need an application in other areas
For more information, visit the government’s Planning Portal.
Similar measures have applied since 6th February 2012. These, however, apply to paving of any size between the house and any street, not just front gardens.
While the law mentioned above should be sufficient for most domestic driveways, contractors and those undertaking extensive or public projects should be aware that there is the Flood and Water Management Act 2010. This sets out the requirements of Sustainable Urban Drainage (SUDS).
Interpave: news about the implementation of the Act
Defra: information on Flood and Water Management Act 2010