BS8485:2015 is the British Standard that covers the design and installation of gas protection membranes within new buildings. These guard against carbon dioxide, methane and other gases entering buildings, collecting in poorly ventilated areas and either causing an explosive, toxic or asphyxiation risk.
Ground gases can be caused by a wide range of sources; include natural soils, brownfield site contamination or nearby landfill sites or buried waste. Their possible existence is likely to be indicated by a Phase 1 desk study, which may be triggered by a planning condition or an NHBC LQ03 Contamination Condition (or similar). Here at Geo-Integrity we can aid you with such possible development problems all the way from Phase 1 Desk Study, through investigation, monitoring and reporting (and now verification).
If harmful ground gases are encountered protection measures will need to be designed in accordance with BS8485:2015. The design will depend on the amount and concentration of the gases (sites are given a Characteristic Situation dependent on the severity - CS1 being the least severe and CS6 the most severe). A common case is a CS2 where a gas protection membrane and underfloor ventilated void would be sufficient in most cases to mitigate the risk.
However, in BS8485 it also states that membranes must be "verified in accordance with CIRIA C735", a fact that more councils are now insisting on. C735 is another guidance manual produced by CIRIA called "Good practice on the testing and verification of protection systems for buildings against hazardous ground gases". Here at Geo-Integrity, following more staff training, we can offer our clients a verification service, which is site specific, but generally entails a pre-verification plan, site visits during the construction phase (with possible integrity testing) and a post verification report that can be forwarded onward to the relevant regulators to prove your compliance with planning/building control conditions.
If you have any ground gas problems on your site drop us a line on this email or phone Murray on 07858 367 125