Radon Protection for Your Extension

Most people reading this don't need radon protection. That's the first and most important thing to understand, because the building forums are full of homeowners who've spent money on a sump and a heavy-grade membrane their postcode never required. Radon is a property-specific requirement, not a regional one in any loose sense. Check your postcode first, and if it comes back below the threshold, you can skip the rest of this page and lay a standard floor membrane like everyone else.

Radon is a naturally occurring radioactive gas. It comes from the slow decay of uranium in certain rocks and soils, it's colourless and odourless, and it seeps up out of the ground and accumulates indoors at floor level. It's the second-leading cause of lung cancer in the UK after smoking. That sounds alarming, but the practical response is undramatic: in the small proportion of postcodes where ground levels are high enough to matter, you build a sealed barrier into the floor and, in the worst areas, a pipe that can vent the gas if a later test shows you need it. That's the whole of it.