Permeable Paving in Auckland

Permeable paving lets rainwater pass down through the surface and soak away into the ground beneath, instead of running across it to a gully trap. On a consented job in Auckland that is usually why it is specified: it reduces the impervious area the stormwater design has to account for, and it slows the rate at which runoff reaches the network. On a private driveway or courtyard the reason is simpler. No puddles, no silt washing across the surface after heavy rain, and no sheet of water running down towards the garage door.

Pavecraft has been laying permeable surfaces across Auckland for over 20 years, from a single house driveway through to visitor parking, overflow parking and fire access lanes on commercial sites. We are the preferred installer for Firth and Jagas. Because we also do our own excavation, base course and drainage, the part of a permeable system that does the actual work - the open graded basecourse underneath - is our responsibility as well as the surface you can see. That is not a small distinction. A permeable paver laid over the wrong base is just an expensive paver.

The permeable systems we install

• Permeable interlocking concrete pavers - these look like an ordinary paved driveway, but they are laid with widened joints filled with fine chip so water passes between the units rather than over them. The usual choice where a permeable surface still needs to read as a normal paved driveway or courtyard.
• Gobi blocks and grass block paving - open cell concrete grids filled with topsoil and grass, or with chip. They carry vehicle loads while staying mostly green, which is why they suit overflow car parks, fire access lanes, swale edges and the parts of a site that have to be trafficable without being sealed.
• Porous and permeable concrete - a poured surface using an open graded mix that water passes through, for paths and areas where a jointed paver is not wanted.
• Channel and surface drains - most permeable installations still need a collection point somewhere. We install channel and surface drains, cesspit connections and subsurface drainage as part of the same job. See kerbing and drainage.

What makes a permeable surface last, and what makes it fail

Permeable paving fails in one way far more often than any other: the voids silt up. Once fine material has filled the joints or the cells, water stops passing through and the surface starts behaving like a sealed one, usually within a few years rather than a few decades.

Most of that is decided during construction rather than afterwards. The open graded base has to be clean and kept clean, the subgrade has to be separated from it so fines cannot migrate up into it, and silt from the rest of the site has to be kept off the finished surface until the job is done. On a live construction site that takes sequencing rather than good intentions, which is one of the reasons we prefer to do the excavation and the surface ourselves.

After handover it is straightforward. Keep the surface swept, do not stockpile soil, sand or mulch on it, and have the joints or cells topped up with clean chip if they drop. A permeable driveway that is looked after will outlast the reason it was installed.

Permeable paving and the stormwater design

Whether a particular site needs a permeable surface, how much of it, and what has to sit underneath it are questions for the project engineer or Auckland Council rather than for us. What we do is install to the specification, and tell you early if what has been drawn is not going to be buildable on the ground you actually have. We are also happy to show you the products in place before you commit to one, because permeable systems look quite different from each other once laid and a sample board does not always make that obvious.

What drives the cost

The paver itself is rarely the largest part of the number. Depth of excavation and how much material has to be carted away, the thickness of the open graded base, edge restraint, drainage connections and machine access usually matter more. That is also why a permeable driveway and a standard paved driveway can be much closer in price than people expect on an easy site, and much further apart on a tight or wet one. We quote the whole build rather than just the surface, so the figure you get includes the part that ends up underground.

Where we install it

Permeable surfaces turn up across most of what we do. Subdivisions where the stormwater design requires it, retirement villages and schools with large areas of hard surface to account for, business parks and car parks, and private driveways and courtyards across the North Shore, West Auckland, the central suburbs and north to Warkworth. For the full range of surfaces we lay, see paving services and concrete driveways.