In short: A vapour barrier only protects the parts of the slab it actually reaches. On a Fraser Rise pre-pour it stopped before the edge beam.
One layer, all the way under
The polythene under a slab keeps ground moisture out of the concrete. On a Fraser Rise waffle pod slab we found it ending before the bottom of the edge beam, so a strip of the slab would have been poured straight onto the soil.
Holes left open
The same visit found punctures in the sheet with no patch or tape over them. A barrier with holes is not a barrier, and fixing it is a roll of tape before the pump arrives.
Mesh and set downs
Elsewhere on Fraser Rise slabs we have recorded mesh sagging between chairs, so the concrete cover would vary, and a shower recess set down not yet formed. Each is a pre-pour fix and a permanent problem once the concrete is placed.
Melton context
These were slabs going in among the new Aspire, Taylors Run and Samara streets. Findings are cited to the Housing Provisions and the Guide to Standards and Tolerances 2015, and the Building and Plumbing Commission's dispute resolution service is the next step if a builder will not act.
Written by our local inspection team from work carried out in Fraser Rise. Licensed building practitioners, Building & Plumbing Commission registration CDB-U 53425.
