Case Study:  41 Dwelling housing site – Belfast

This site was a Characteristic Situation 3 risk site.  The site encompassed a passive ventilation system below the slab and use of a welded proprietary gas barrier over the top of the slab.  The level of validation required:

  • Independent inspection of the passive ventilation system
  • Integrity testing of all seam joints and penetration details to ASTM D4437
  • Independent inspection of all membrane installations

The main contractor used a local specialist installation contractor which meant it was possible to bring the integrity testing requirement down from all plots to the first 10 plots and then 1 in 4 thereafter.  Providing the installation was kept to a high standard during visual inspection.


All welded joints of the membrane were integrity tested by air lancing to ASTM D4437 where any failures were marked for remediation before re-testing once repaired.