Does anyone know the correct way to install a radon DPM agaist an existing wall? Is the detail in this immage acceptable? http://img215.imageshack.us/img215/1970/radonyr9.jpg
Probably will need a mastic (non setting) seal against the existing wall after the oversite is in. Just trim back the polythene to create a 30mm dpm upstand, hoover out all dust and debris and mastic seal. Screed will bury all this.
No, A radon barier must extend over the cavity to the external leaf. http://www.plyload.co.uk http://www.visqueenbuilding.co.u http://www.radoncouncil.org/BARRIERS.HTM http://www.resapol.com/datasheets/PROOFEXRADONBARRIER.PDF http://www.cavitytrays.co.uk/pdf/membranes/Radon-Barrier.pdf Check these out.
Hi kaintheo, The barier will extend over the cavity to the new external leaf. The existing wall is currently an external cavity wall but will become an internal wall of a new room. dk
As long as it forms a tray in the cavity, is lapped and tapped to the membrane under the floor and sits in the bed joint of the external leaf by at least 20mm then you should be fine. Besides, building control will inspect and give the yey or ney. Good luck.
eh? What about where the membrane meets the old existing cavity wall? This is what we are questioning. It is normal to run it up the wall and trim off later but this leaves a 'leaking' join. This is where mastic (polysulphide or similar) would do the job. You seem to be talking about the NEW cavity walling where a tray is formed as you say.
Yes I am, In this case I would chase out 30mm of the bed joint and insert the membrane, seal with an appropriate sealant and then the screed/insulation will cover as you already said.