Box Hill Building
Inspections

Pinholes: the smallest defect that costs the most

A hole the size of a pen tip in the one layer that must not have holes.

Box Hill 2765 · 25 February 2026

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In short: The most common waterproofing finding on our Box Hill jobs, and the least visible.

What a pinhole is

A break in the applied membrane about the width of a pen tip, usually a burst bubble in the coat or debris trapped beneath it.

Where we find them

Shower recesses, hobs, niches, entries and powder rooms. Sometimes several in a single bathroom on the same job.

Why they get past

They pass a glance from the doorway. Finding them means going over the membrane closely, with light, which takes time and is why it is a stage of its own.

What happens later

Water passes through, tracks under the screed and turns up as a damp skirting in the adjoining room a year or two after handover.

The economics

Closing a pinhole before tiling takes the waterproofer minutes. Finding it afterwards means removing tiles, screed and often the shower itself.

Written by our local inspection team from work carried out in Box Hill. Licensed building practitioners.

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FAQ

Questions Box Hill owners ask about this

Is one pinhole really a defect?

Yes. Continuity is the entire function of the membrane, so a single break is a path for water.

Can the waterproofer just patch it?

Usually, with an additional coat over a properly prepared area, before any tiling starts.

Do all builders accept this?

Most do, because the item cites AS 3740 and the remedy is cheap at that moment. The report gives them the location and the clause.

When can this be inspected?

Only between the membrane curing and the first tile going down, which is often a two or three day window.

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