A Sealed Ground Under the House in Albury-Wodonga

The National Construction Code names sealing the ground in the subfloor space with an impervious membrane as one way to meet its extra requirement where the ground is excessively damp or floods often, and its vent table allows ventilation rates to be halved if the ground is sealed. The reason, in the Board's words, is that humidity in the space is then not affected by moisture from the soil.

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What ground membrane in Albury-Wodonga actually involves

The Australian Building Codes Board's NCC 2022 (the edition NSW applies) and NCC 2025 (Victoria's) both list the impervious membrane among the options in clause 6.2.1(5), alongside increasing the ventilation by 50 per cent. The Board's explanation says the table allows subfloor ventilation rates to be halved if the ground within the subfloor space is sealed by an impervious membrane (read 7 October 2026).

What the code does not say here

We read no page that says what material, thickness or laps a membrane needs, or whether a membrane suits a particular house, so we state none. Ask the provider what they will lay, how they will deal with the edges at piers and walls, and what happens to water that arrives on top of it.

A black plastic sheet laid flat over the soil under a timber floor with brick piers rising through it — ground membrane under the house, Albury-Wodonga. Illustrative example.

Questions for the quote

Ask whether the quote is for a sealed ground, for more vents, or for both, and why. Ask which side of the river the provider has treated the house as being on, since NSW and Victoria are on different code editions. The rules page explains the difference.

Both councils record water arriving from outside the subfloor: see the damp ground page. A sealed ground changes what the soil can add to the space; it does not change where roof water goes.

The edge of a plastic sheet lapped up a brick pier and weighted with loose bricks — ground membrane under the house, Albury-Wodonga. Illustrative example.

Albury-Wodonga subfloor costs and rules check