Finding the vapour barrier gap far too late

In short: A barrier missing in sections is only fixable before the concrete. After that it is a permanent unknown.

What the barrier does

It separates the slab from ground moisture and only works as one continuous layer beneath the whole pour.

What we recorded

Vapour barrier missing in sections along a Craigieburn slab edge, visible at frame stage because the edge was still exposed.

Why the timing hurts

By frame stage the concrete had been down for weeks. Nothing about what sits beneath it could be changed.

What a pre-pour inspection would have cost

An hour on site the day before the pour, and a few metres of plastic to correct.

The general lesson

Every slab finding is a pre-pour finding. There is no second chance at any of them.

Written by the Owner Inspections team from inspections carried out in Craigieburn. Licensed building practitioners, Building & Plumbing Commission registration CDB-U 53425.

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Questions Craigieburn owners ask about this

Can the barrier be repaired afterwards?

Not beneath a poured slab. What can be managed afterwards is drainage and moisture around the perimeter, which is mitigation rather than a fix.

What are the consequences?

Moisture movement into the slab, which typically shows up much later as flooring lifting or persistent damp at the edges.

How do I avoid this?

Book the slab pre-pour stage and tell us as soon as a pour date exists, because that date moves and the window does not reopen.

Is this common?

Common enough that the vapour barrier is the first thing checked at every pre-pour inspection we attend.