Because of global warming and other environmental considerations, the government decided to change legislation concerning the modification or the building of pavements. This has been done mainly to stop flooding due to rainwater flowing into overstretched sewers.
As mentioned the designs should enable water to drain freely into the ground. As explained earlier, a permeable surface should be used if the area to be paved is greater than five square metres. This is not always the case if your design allows water to drain into the ground of your property without it draining into the highway sewers.
If for a particular reason an impermeable pavement is necessary then planning permission must be applied for.
