Civil Engineering Association

This manual is a practical guide to current good practice for the detailing and the construction of passive soil gas protective measures for new and existing residential development. It does not contain advice on the design of passive or active protective measures for specific gas regimes, nor does it provide information on active gas protective systems or inground protective measures external to the building, such as the use of venting trenches or barriers. The gases considered are principally methane, carbon dioxide and mixtures of the two. The sources of both gases are typically:
l fill or made ground containing biodegradable organic material;
l soils with a high organic content, eg peat;
l coal measures and/or underground mine workings;
l soil gas migrating from a nearby source.
The details are also applicable to radon and, subject to the suitability of the materials, VOCs. This manual should be used only after the gas regime for a site has been fully characterised and it has been confirmed that the passive protective measures contained in the manual are appropriate. Passive protective measures are the combination of utilising the ground floor as a barrier against the ingress into the building of soil gas, and sub-floor venting which dilutes and disperses the soil gas. The investigation and assessment of a soil gas regime for a specific site and the selection and design of an appropriate gas protective system or systems requires specialist advice from a suitably qualified and experienced engineer or scientist. Every site is unique; this manual does not provide advice on the assessment of sites or the selection of the most appropriate protective measures. The reader must, therefore, make appropriate and specific assessments with a geotechnical and geoenvironmental investigation. Guidance on site assessment is in the publications listed opposite on page iv, and on page 66. When applying the details in this manual, the designer must always check that the details for gas protection do not conflict with Building Regulations for other design and construction criteria, for example thermal insulation, accessibility or damp and water penetration.