GAS CONTAMINATION

Landfill (methane gas)

When left to dissipate in the open air, methane gas presents no harm but this gas has a tendency to migrate through fissures in rocky soils and turn up where you least expect it. Building within a radius of 250m from a landfill site will invoke requirements for methane-sealed barriers, where the gas could migrate to form a potentially explosive mixture in the cavities and subfloor voids of a house. in different soils, the risk of methane migration varies tremendously. in wet sticky clay it may scarcely travel a metre or two, whereas in a fissured chalk or gravel it could migrate for considerable distances.

Radon

in parts of the country a natural radiation called radon is present. Background radiation is present in everyday life from quite a few different sources, ranging from mobile phones to cosmic rays! So why single out radon as a threat to our health and take precautions when housebuilding against it? Studies of those exposed to high levels of it suggest they have a higher risk of developing lung cancer and since radon is a ground-bearing gas, keeping it out of the home isn’t complicated or particularly expensive.

The geology where radon is present is generally granite, and could be chalk or other rocks. Hence, areas like the southwest of England have the highest levels, but it results from the uranium decaying in all soils and rocks.

As radioactive gas, the particles can be inhaled and attached to the tissues of our lungs, irradiating them, and of course the higher the levels of radiation, the higher the risk of it causing us harm. The government has set an ‘action level’ and prepared an atlas of the country indicating the areas where radon prevention is needed for all new homes.

You can carry out a free postcode check online or obtain a site report at ukradon.org for £3.90 which identifies if basic or full protection measures are needed. The levels that could enter your home will vary depending on the inside and outside temperatures, but are normally higher at night. Ventilation can help to disperse radon, but it’s better to stop it getting in to begin with, by using a sealed membrane in the floor construction and taping all the joints and gaps.