Sustainable drainage with concrete flagstones

Concrete paving slabs can allow rainwater to drain quickly and safely

You may have heard of sustainable urban drainage systems, or SUDS - driveways and paving methods that allow water to be carried into the ground, rather than leaving your property as surface run-off.

The idea behind these is simple as, unless water has a way of finding its way into the earth or the sewerage system, it can accumulate as large areas of standing water.

Concrete flagstones can provide you with an excellent option, as styles like York stone paving have wavy edges, similar to those of natural stone.

As they do not fit snugly against one another, York stone paving slabs leave small gaps through which the rainwater can escape, allowing it to penetrate into the earth as it would if your garden were still bare earth or lawn.

Other paving options - particularly block paving - are now emulating this wavy-edged approach, in order to prevent block-paved driveways from flooding in heavy rain.

How do I make sure my patio drains properly?

To give your patio the best chance of draining well in the rain, there are several steps you can take - and some of them fly in the face of the advice you might read elsewhere.

Firstly, you may wish to use the surface of your patio to guide rainwater in a particular direction; to do this, simply make sure that your patio slopes towards your chosen flowerbed, drainage ditch or sewer inlet.

Laying on a bed of sand makes it quite easy to make minor adjustments to the slope of your patio, and is probably the way you've been told to lay your concrete paving slabs if you've read any tutorials or asked friends and family who have laid a patio of their own in the past.

The second option is a little different, however, as it allows rainwater to continue draining directly downwards into the earth.

In this approach, you would lay your concrete slabs on to gravel, which in turn would be spread over a permeable membrane, rather than any kind of non-permeable plastic sheeting.

Leave a small gap between the slabs as you lay them and fill the joints with loose gravel, rather than packed sand or mortar, which can both prevent water from draining through.