Holes, laps and pipes: vapour barrier faults on Strathtulloh slabs
The vapour barrier under a slab is invisible for the life of the house. These are the membrane faults we find before Strathtulloh pours.
In short: A torn or unsealed vapour barrier lets ground moisture into the slab and the floor finishes above it. It takes minutes to fix before the pour and is impossible to fix after.
What the barrier does
The polyethylene sheet under a slab stops moisture rising from the clay into the concrete. Without it, damp can reach floor coverings and the base of walls, and on clay ground there is plenty of moisture to rise.
Punctures left open
Pods, boots and steel tear the sheet during set-up. The Housing Provisions require punctures to be patched with extra polyethylene and taped. On one Strathtulloh slab we recorded several holes left as they were.
Pipes without a seal
Every plumbing and drainage pipe passes through the barrier. Each penetration needs a sleeve or tape so moisture cannot track up beside it. Untaped pipes are among the most common slab items we record.
Stopping short of the beam
The membrane has to run under the slab and down the beams to ground level. Where it stops at the top of a beam, moisture can wick into the concrete edge.
What the builder does about it
These are quick repairs: a patch, tape, a sleeve. Pointing them out the day before the pour is all it takes.
Written by our local inspection team from work carried out in Strathtulloh. Licensed building practitioners, Building & Plumbing Commission registration CDB-U 53425.
