Lars P

Splendid - spoke to BCO and Rodding point riser in the kitchen is the way to go - thanks all for your input. Onwards to the next obstruction.

this is as is : so could simply remove chamber (black cylinder) and add double sealed inspection hole under kitchen sink or remove chamber and replace with the below - of course with a rodding eye fitted on the external end of the pipe. All 200mm radius bends

In digging out for block and beam for new extension to kitchen just found an 30cm wide ish chamber hidden under the existing paving. It's not on the public sewer. Could I add a rodding point to the incoming 110mm piper under the kitchen sink or do I have to install a new rodding point from outside the new extension ? I'd replace the chamber with a new y connector and connect it to a straight run to a rodding eye outside the extension - but as it's a terraced house it can't just be to the side of the extension instead a 180 degree long radius bend is required. Seems counterproductive - but of course don't have to deal with a kitchen drain clog from within the kitchen. Has never happened in the last 20 years at least. Any thoughts ? Cheers

found this on LABC https://www.labcwarranty.co.uk/technical-blog/damp-protection-for-concrete-floor-beam-systems - but their website is nowhere to be found

It's actually not Radon driving this palaver, but the fact that there is an old landfill 245.5 meters away from my front door - so my house is in the 250m 'buffer zone' - even though the extension in the back garden will be by 1m2 or so. Talking about measuring elastic band with a caliper So did you do something along these lines - just with the insulation and the slab swapped around - and then 100mm out though the foundation - and the membrane through the foundation as well ?

Great - thanks Redbeard - let me try pick your brain. First of all - the main house has no gas protection whatsoever - only a not very tight fitting DPM over the block and beam floor, - so seems somewhat pointless having to go through the effort of protecting the extension as it will be one big room. Anyway. Below is the design so far but I seem to have an issue with the anchor bolts penetrating the membrane. Also - I'm unclear how the membrane should be finished off where it meets the outside wall of the main house. Any ideas ?

Hi diyers and pros Does anybody have experience in with this topic.

Born with the 'I can do that' gene. How hard can it be. We'll, it's not just old fashioned logic and pragmatism all the way. Started out with a simple design, now having to build Fort Knox.