Radon sump

Pygmie

Sorry if this question has been asked already. We we getting a quote from a builder for an extension and he asked if we wanted a radon sump. We have no idea what this is! I don't think we live in a particularly radon prone area. Is it necessary to have a sump???

delfagio

Yes, tell him to put a sump in. You would be better safe than sorry. I'd imagine your existing house has it too.

Basically, a radon sump is basically a box which is placed in the hard-core stone under the subfloor of a house. A 4" pipe runs from this box to the side external wall of the house which allows any radon gas building up under the subfloor to escape to the outside air via the 4" pipe. This then means no radon gas will get into the house and poison the inhabitants.

You need radon barrier under the concrete subfloor also which acts as a barrier to prevent any radon getting up through the subfloor and into the house.

It's only small money so I would get your builder to put it in, a few lengths of 4" pipe may only be 50euro, about 30euro for radon sump and the cost of the sump cap and 90degree 4" bend which again may be only 30-40euro.

Cost for Labour to put it in would be minimal.

Radon barrier comes in rolls so depending on the size of your extension you will have to check the price of this. More than likely your builder would have priced for either radon barrier or Damp proof membrane in his price so this wouldn't change too much if any.

Make sure you test for radon in your house when the extension is finished

Gumbo

I always recommend putting one in along with the radon/DPM layer.