The Hidden Risk in Gas Membrane Design: Rethinking the Use of Aluminium Foil

In the construction industry, gas and vapour barrier membranes play a critical role in protecting buildings and their occupants from harmful ground gases such as methane, carbon dioxide, and radon, as well as hydrocarbon vapours on contaminated sites. For many years, aluminium foil–encapsulated membranes have been widely regarded as an effective solution due to their strong resistance to gas permeation.

However, evolving industry understanding is now challenging the long-term reliability of these traditional systems, particularly when exposed to real-world site conditions.

The Problem with Aluminium Foil Membranes

At the heart of the issue lies a material compatibility challenge. Aluminium, while highly effective as a gas barrier, is inherently vulnerable in alkaline environments.

When concrete is poured, it creates a highly alkaline condition. If the protective polyethylene layers surrounding the aluminium foil are compromised—even by minor punctures, abrasions, or installation damage—the foil can be exposed. Once this occurs, the consequences can be significant:

Corrosion of the aluminium layer due to the alkaline nature of wet concrete
Delamination of the membrane structure, reducing integrity
Loss of gas and vapour resistance, undermining the membrane’s core function

Even small, often undetectable defects in the protective layers can initiate this process. As a result, industry guidance increasingly advises against placing aluminium foil membranes in direct contact with concrete slabs or screeds.