Water Under the House in Mona Vale: Old Terracotta Pipes and No Subsoil Drainage

The situation

The owners of this Mona Vale home had water sitting against the side of the house and slowly working its way through the brickwork. Underneath the house, it was worse: a small stream of water running across the ground and an underfloor space that stayed damp. It wasn’t a sudden leak, it had been building for a while, with water finding the easiest path it could into the house.

What we found

The stormwater pipe running from the house to the street was old terracotta piping, the type commonly used decades ago before PVC became the standard. Over the years, tree roots had grown into the joints and cracked the pipe in multiple places along its length. Instead of carrying rainwater straight out to the street, the broken pipe was leaking that water into the surrounding ground the whole way along its run, right next to the house.

The pipe was part of the problem, but not all of it. The house also sits on a small slope, and groundwater flowing down the hill was collecting against that side of the wall. Between the leaking pipe and the groundwater running downhill into it, water was building up against the brickwork and finding its way through and under the floor.

The fix

We replaced the entire run with brand-new PVC piping to the street, and connected the downpipes directly into it. That meant every drop of rainwater coming off the roof was now going straight into a sealed pipe, not soaking into the ground beside the house.

The side of the house where the water problem was worst also needed its own dedicated fix, since water had clearly been sitting against that wall for some time even before the pipe failed. For that, we:

• Dug a trench along the problem side of the house, down to the footings (the base of the wall that sits below ground).
• Cleaned the wall back and applied Drizoro, a waterproofing coating that bonds to brick and concrete below ground to stop water pushing through the wall.
• Installed a subsoil drainage system in the trench, to catch any groundwater before it can reach the wall.
• Connected that drainage into the new PVC stormwater line, so all of it flows away to the street instead of sitting against the house.

The outcome

With the new pipe carrying roof water straight to the street and the subsoil drain catching groundwater along the wall, there was nowhere left for water to build up against the house. The other side of the house, which hadn’t had the same drainage done, continued on without issue after our work, confirming the fix on the problem side had done its job.

Water finding its way through a wall or pooling under the house? Our stormwater drainage team traces where the water’s actually coming from and fixes the pipe and the drainage together, across Mona Vale and the rest of the Northern Beaches.