In short: The plastic under a slab is the first thing built and the first thing buried. On Strathtulloh slabs we keep finding it holed, untaped or cut short.
A sheet with a lot of holes
Every slab starts with a polyethylene vapour barrier laid over the prepared ground. By the time pods, steel and boots have crossed it, it is rarely whole. The Housing Provisions say punctures must be patched with more polyethylene and taped. On a Strathtulloh slab in August 2025 we recorded punctures that had been left open.
Where the plumbing comes through
Each waste and water pipe passes through the barrier. A sleeve or tape around it stops moisture tracking up beside the pipe. On a February 2026 slab several penetrations had neither, which is one of the most common items on our pre-pour lists.
Down to the bottom of the beam
The barrier must run under the slab and down the edge and internal beams to ground level. When it stops short, moisture can wick into the concrete edge. We found exactly that on a Strathtulloh slab inspected in 2025.
Ten minutes before, never after
A patch, a roll of tape and a sleeve fix all three. Once concrete covers the sheet there is no repair. That is the whole case for inspecting the day before the pour.
Written by our local inspection team from work carried out in Strathtulloh. Licensed building practitioners, Building & Plumbing Commission registration CDB-U 53425.
