Level 4 Rooftop Planter Box — Loose-Laid Ballasted PVC System

Completed fleeceback PVC membrane to the level 4 planter box — welded upstands, outlets and corner detailing

The object

A new residential building under construction in Sydney, with a large planter box on level 4 — directly over occupied living space below.

The problem we solved

A planter box at level 4 sits in permanent contact with saturated soil and irrigation water, over habitable space — so the waterproofing had to be genuinely long-life and fully verifiable. That is why a welded PVC sheet system was specified rather than a liquid-applied one.

Our scope of works

Loose-laid ballasted PVC system: geotextile separation layer, then a fleeceback PVC sheet membrane hot-air welded throughout — base, internal walls, corners, upstands and drainage outlets. Termination into a chased reglet: a metal angle set into the chase, welded to the membrane, with the entry point into the chase sealed.

Special features / difficulty

Compartmented geometry with multiple outlets and upstands, worked on an active construction site at height. The critical detail was the reglet termination — the angle-to-membrane weld and the sealing where the angle enters the chase determine whether the top edge holds long-term.

The result

Handed over fully welded and watertight, ready for the drainage and soil build-up. Installed by a two-man crew — the company owner and the lead installer.