Permeable Surfaces: What Counts, and Where to Find It
Your plans get told they need more permeable surface. The driveway you have to pour anyway can supply it instead of costing you room elsewhere.
Ground that drinks, ground that doesn't
A permeable surface is simply ground built so rain soaks into it instead of sheeting off. Councils set a ceiling on how much of a block can go under roof, slab and paving, and a floor under that: a minimum area that has to stay open to water. On a narrow infill site, that floor gets eaten fast by the house footprint and the driveway before anyone's touched the garden.
- Counts: lawn, garden beds, and pervious paving where a designer can show the drainage and the authority accepts it.
- Doesn't: roofs, sealed concrete, standard paving.
Lawn and garden beds are the easy win if there's room for them. Where there isn't, the driveway becomes the lever, because it's mandatory regardless of what it's made from.
Victoria names it; elsewhere it's a conversation
Clause 55 guidance in Victoria asks for at least 20 per cent of a site to let rain through to deep soil, and lists a pervious driveway or path as one way to reach it. Other states and councils write their own versions of the same idea. We will work with anyone that wants the Permcon product; we just need to make a design that suits their needs. Check with your planner before the drawings are final, because the council decides what counts on your particular site.
Pour the mandatory surface pervious
On a small block, the driveway is often the largest hard surface after the roof. In ordinary concrete, every square metre of it comes straight off your permeable-area total. Poured as a permeable concrete driveway, at 25+ MPa and without a puddle standing on it after rain, those same square metres go back onto the plan's side of the ledger and can free up room elsewhere in the design.
What holds the water, and who checks it
Rain passes through the slab into a base of clean screenings, which hold 37 litres to 42 litres per square metre under a typical driveway before it soaks away or bleeds out through an under-drain on tighter ground. Council's engineer wants figures for the actual site, so we put the surface infiltration rate, the base storage and the build profile in writing; the wider data set sits on our technical page. Smaller Victorian sites are usually run through BlueFactor, which took over from STORM, and we can show a designer exactly where the driveway sits in it, with more detail on our Victoria page. Larger projects, and Queensland councils that ask for it, model in MUSIC instead, and Permcon is MUSIC certified: the parameters are available to whoever's running that model, on request.
Permeable surface questions
What counts as a permeable surface?+
Lawn, garden beds and other planted ground, straight away. Pervious paving too, where the design shows the drainage and the authority signs off. Sealed concrete, standard paving and roofs don't make the cut. Your area's own planning controls set the exact line.
Is gravel permeable?+
Usually, provided it isn't laid over plastic sheeting or a sealed base. As a driveway it's a poor choice: it ruts, spreads onto the footpath, and gives bins and prams a hard time. A pervious concrete driveway counts toward the same area and doesn't move.
Does a permeable surface replace a detention tank?+
Sometimes it does the job outright. The base beneath a pervious surface stores water, shrinking the tank and pipework on some sites, removing the need on others. Which one depends on the stormwater design your council approves. Send the plan through and we'll size the base against it.
Can existing concrete be made permeable?+
Not by sealing over what's there. The old slab comes out, and a pervious one goes down on a stone base in its place. On a renovation, that's often the easiest way to claw back permeable area without sacrificing the driveway.
Send the plan, permeable-area condition included
We'll go through the site and the drawings, work out a profile for the driveway or paths, and put the infiltration and storage figures in writing for your designer and council to check.
Check if permeable concrete suits your site
A few quick questions about your site. You get a straight answer about whether permeable concrete is the right call, including when it isn't, before anyone asks for your details.
What are you surfacing?
Tell us about your project
Tell us where the site is and what you're planning. An estimator from your state team will call you back, look at the site with you and give you a real figure, from a single driveway to a council car park.
Pervious surfaces on real sites
