Assessments for house extensions

Landfill and ground gas can be a potenhal hazard to health. If there are plans to make structural alterations to a property that is within 250 m of a known landfill site or within an area of suspected ground gas it is likely that the local council will require gas protection measures to be installed. 

In other situations where there is the potential for gas but the risk is low and the existing property does not have gas protection measures then protection to the extension may not be required. 

If the property already has gas protection measures or the local council has put a condition requiring gas protection measures on the planning approval for the extension it is important that such measures are installed. Such a condition will only be placed on a planning approval if the council believes that the property and its occupants may be at risk without these protection measures. 

If a building contains a certain specification of ground gas protection measures then an extension should not be constructed without protection or with measures of a lower specification. Doing so may compromise the gas protection measures to the whole property. Therefore it is important that every property extension this is constructed should contain gas protection measures to at least the same specification of that in the existing building. 

It should also be ensured that the construction of extensions does not in any way compromise the effectiveness of existing gas protection measures (e.g. by blocking vents to the underfloor void or damaging existing membranes). 

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