Auckland Stonemasons protect pohutukawa from the rising tide with expertly crafted sea wall

Located on Auckland’s North Shore, this residential clifftop property includes a section of the shoreline below, with a walkway that winds down the cliff and out onto a small, private lookout home to several pohutukawa trees. Aware of the changing weather patterns and increased likelihood of tropical storms, the property owners were concerned about erosion eating away at this valuable slice of land. In the business of protecting land with their expertly crafted sea walls, Auckland Stonemasons provided the perfect solution.

“The client was concerned about protecting the pohutukawa trees and stopping them from being washed away in the event of a storm,” says Len Lavas, master stonemason and director of Auckland Stonemasons. 

“We visited the property to have a look, see what the issues were, and discuss the best solution with the client. Once we had that conversation we brought in our brilliant engineers, Davis Coastal Engineering, who handled the engineering side of things and the council consent. Once we had received consent we went ahead with the build.”

Building with the tides

When building a sea wall, you’re not only navigating the sandstone terrain and weather but the fluctuating tides, too. 

“We excavate into the sandstone about a metre down, because the sandstone still erodes and you can lose about 100 mls of it every 10 years, and then we build from there. We have to build between tides, so when the tide is in we can’t do much, and when the tide is out we can do lots. Of course, it depends, once we’re at a certain height we can build the top parts of the wall when the tide is in, but when we’re starting with the bottom there are some days we can’t do anything, or we start early in the morning and take a break for a few hours before coming back in the afternoon,” Lavas explains. 

The walls the Lavas’ build are not too different from those their grandfather built, as many of the traditional stonemasonry methods are still used today. The main difference is that, now, the walls are grouted the whole way through, and some — like the one built for this North Shore property — use recycled stone and recycled concrete slabs.

“All of our walls are basalt because it doesn’t get eaten away by the sea. Most of the basalt we use is recycled. It gets excavated and then would otherwise be sent straight to the tip, so we take it and split it into blocks to build sea walls. The back of the wall is built using old concrete footpath slabs. We put a layer of wet concrete, a layer of these slabs, a layer of wet concrete, and so forth. It’s incredibly strong. It also means 90% of the materials in the walls are recycled.

“These are traditional walls that we’ve made stronger. We can do things differently from the old days because we have machinery. In the old days, it was a nightmare to dig the trenches for the base of the wall. You would be doing it by hand, and then the tide would come in and fill it with sand and then you would have to dig it all back out,” Lavas says.

Thanks to modern machinery, Lavas and his team can prepare the bank, dig a trench for the base of the wall, and build the wall base all before the tide comes back in.

A satisfying result

“The owner was thrilled with the finished wall,” Lavas says. “Before the build, he was unable to get down to the sea, but now he has a beautiful platform where he can keep his boat and swim on nice days.”

With the support of the sea wall, the land is no longer at risk of erosion, and the pohutukawa trees are safe from the tug of the tide. 

Because sandstone is still susceptible to erosion, there’s a chance that, in 150 years, someone may need to dig under the wall and build extra layers of support. This, Lavas says, is no big deal. He’s done a few jobs on old walls where erosion has eaten away at the stone below, and it’s simply a case of building down. Chances are, a relative of Lavas will be the one to take on that maintenance job.

Learn more about Auckland Stonemasons.