Permeable Driveways: Which Surfaces Actually Let Water Through?

A permeable driveway lets rainwater pass through the surface and soak into the ground underneath, instead of running off into the road or the drains. The realistic options for a house are resin bound on a porous base, porous asphalt, permeable block paving, and gravel or reinforced grass. Every one of them depends on a free-draining base below: get that wrong and a "permeable" surface behaves like a sealed one.

What makes a driveway permeable?

Water has to get through every layer, not just the top. A conventional drive is built on MOT Type 1, which the government's front garden guidance points out contains a lot of fine material (sand and silt) that stops water passing through easily. A permeable drive sits on an "open graded" stone instead, such as 4/20 or Type 3 sub-base, made of larger pieces of stone with space between them to hold water while it soaks away.

The same guidance describes a typical construction of around 200-250mm in total, with about 150mm of compacted sub-base laid over a geotextile membrane. That hidden part is where most of the difference between a permeable drive and a sealed one actually sits.

Permeable driveway options

Resin bound on a porous base

Resin bound is natural aggregate mixed with clear resin and trowelled out by hand. Each stone is coated, but the gaps between stones stay open, so water drains straight through into the base. When drainage is the deciding factor on a front garden, the resin drives we lay are usually where the conversation ends up, because the finish and the drainage come in one surface.

The catch is that resin bound is only permeable if what lies under it is. Laid over old dense tarmac or concrete, the water has nowhere to go but sideways. A genuinely permeable resin drive needs a porous base all the way down: clean, no-fines stone (often 4/20) over a geotextile, sometimes with an open-textured asphalt layer on top.

Do not confuse it with resin bonded, where loose stone is scattered onto a coat of resin. Bonded is not permeable and sheds stones over time. We only lay resin bound.

Porous asphalt

Porous asphalt is an open-textured tarmac with voids that let water through, whereas standard tarmac is not permeable at all. The government guidance recommends a specialist supplies and lays it, and our guide to permeable tarmac explains how the mix and base differ.

Permeable block paving

Permeable block paving looks much like ordinary block paving, but water passes through the joint filling in the gaps between the blocks into a permeable sub-base. Interpave, the precast paving trade body, explains that the water is stored in the sub-base and released gradually, and that many pollutants are removed on the way through. We do not lay block paving, but it is a perfectly valid permeable option, and our post asking is block paving permeable explains which block systems drain and which do not.

Gravel and reinforced grass

Loose gravel is one of the cheapest permeable surfaces, though it scatters and is not suited to steep drives. The guidance suggests a strip of block paving or asphalt at the entrance to stop it migrating onto the pavement. Reinforced grass uses plastic or concrete cells to hold the ground up, which suits occasional parking better than a daily school run. For gravel, the guide to gravel driveway depths covers the sub-base and stone it needs.

A sealed surface that drains to a border

Tarmac or pattern imprinted concrete can still meet the rules if the drive falls towards a lawn, flower bed, rain garden or soakaway inside your boundary. The surface is not permeable, but the water still ends up in the ground on your property.

What does SuDS mean on a driveway?

SuDS stands for sustainable drainage systems: dealing with rain close to where it lands rather than piping it away. On a single house it mostly means not sending the drive's water into the road gullies. A permeable driveway is a small SuDS feature in its own right, because the sub-base acts as a short-term store and the ground takes the water at its own pace.

That is also why it matters on a street. Every sealed front garden that drains to the road adds to what the sewers have to carry in a storm.

Do you need planning permission for a permeable driveway?

No, not for a house in England: a front driveway of any size is permitted development if it is permeable or drains to a lawn or border, as the government's permeable surfacing guidance sets out. Flats, converted houses and homes with an Article 4 direction work differently, and our guide to the 5m² front garden rule covers those exceptions.

How permeable drives clog, and how to stop it

Permeable surfaces fail slowly, by silting up. Soil, sand, leaves and grit get washed into the voids and close them. The guidance is practical about it:

• clear leaves, mud and litter before they get trodden in

• brush the surface when dirt collects on it

• never store soil or sand on the drive, and do not let flower beds drain onto it

For porous asphalt and permeable blocks it says a blocked surface can be revived with a small vacuum sweeper or a jet washer. On resin bound, a sweep and an occasional low-pressure wash is normally all it needs.

Does the ground matter?

Yes, a lot. Clay takes water slowly, sandy and gravelly ground takes it quickly, and you will not know which you have until you dig. The guidance gives a simple test: dig a pit 300mm square and 300mm deep, fill it with water, and if it takes more than 11 hours to empty, include a pipe in the sub-base to carry excess water to the roof drains. On very clayey sites that pipe is the sensible precaution. Contaminated ground is different again: if the soil was designed to keep water out, the drive has to connect to the drains instead.

Permeable driveway questions, answered

Is a permeable driveway more expensive?

The surface often costs more per square metre than a sealed one, but you may not need channel drains and a soakaway on top. Compare whole jobs, not surface prices, and ask each installer exactly what is under the finish.

Can I make my existing driveway permeable?

Not by laying a new surface over the old one. Resin over dense tarmac will not drain through. You either dig out and rebuild on a permeable base, or keep the existing surface and redirect the water to a border with a channel drain.

Which option lasts best?

A properly built one. Each surface on this list will outlast a cheap version of another, and the base decides more than the top. Our driveway material comparison weighs the surfaces side by side.

Getting the drainage right first time

Pete and the team have been building drives across Wolverhampton and the Black Country for over 25 years, from our base in Tettenhall, and drainage is part of every front garden we price. On a site visit we look at the levels and the ground and tell you whether a permeable surface, a drained sealed surface or a mix of the two suits the plot. If you would like us to look at yours, get in touch for a free site visit and quote.