Extention Radon DPM

Discussion in 'Builders' Talk' started by dk, Mar 11, 2008.

  1. dk

    dk Member

  2. ­

    ­ New Member

    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.
     
  3. ­

    ­ New Member

  4. kaintheo

    kaintheo New Member

  5. dk

    dk Member

    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
     
  6. ­

    ­ New Member

    kaintheo, this is where the new polythene butts up to the old, existing wall.
     
  7. kaintheo

    kaintheo New Member

    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.
     
  8. ­

    ­ New Member

    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.
     
  9. kaintheo

    kaintheo New Member

    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.
     

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