At the Norwich CPD ‘Centre of Excellence’ on Wednesday 14 November, members in the Eastern region were given a CPD presentation called Ground Gas Protection – Building on Contaminated Land by Aubrey Machin, National Technical Sales Manager (Ground Gas Protection) for A. Proctor Group.
Following a short introduction to the A. Proctor Group and services they offer, Aubrey started off the session by looking at the problem of contaminated land. He summarised the main types of gas we may come across; that building-users need to be protected from under Part C of the Building Regulations. These included Methane (explosive), CO2 (asphyxiant), Radon (naturally occurring carcinogenic gas linked to lung cancer) and Volatile Organic Compounds (VOCs – hydrocarbons – poisonous). This was then explained in the context of the Source-Pathway-Receptor model and delegates were given some examples of real life situations where things went wrong which led to the initial guidance being produced.
The CIRIA C735 2014 – Good practice on the testing and verification of protection systems for buildings against hazardous ground gases guidance note was discussed. The guidance note promotes a risk-based approach to verification and the training of installers. It requires independent verification, independent validation, integrity testing of the installation and also includes advice on site preparation, jointing and barrier types specific to a site.
A basic outline of what is contained in BS 8485:2015 – Code of practice for the design of protective measures for methane and carbon dioxide ground gases for new buildings followed. Firstly, he talked through the potential protection measures such as structural barriers, barrier membrane, void ventilation systems and the potential to use CFD software to model the void ventilation to ensure adequacy.
The NHBC guidance in the NHBC Standards was reviewed and he talked us through site grading i.e. Green, Amber 1, Amber 2 and Red and what this means. Aubrey then briefly discussed CIRIA C748-2014 – Guidance on the use of plastic membranes as VOC vapour barriers and the durability and resistance to damage when plastic membranes are exposed to VOCs and the potential for degradation. Some samples of VOC membrane were passed around the room for assessment by the attendees.
Aubrey finished off the CPD by looking at the critical area of membrane installation such as corner detailing and how pre-formed corners are best to use if possible, jointing methods – hot air welding and taping, stanchion/pipe penetration detailing such as cloaks, ‘top-hats’ and flashings. He then presented some good and bad photographic examples of each. He also looked at a few changes to BS 8485 that are likely to come in soon including the requirement for post installation protection and that membranes will need to be at least 370g/m2 and 0.4mm thick.
The details for future events will be advertised in the e-newsletters and Building Engineer in the usual way so keep your eye out for them; and please note that you must book your place through the Eventbrite ticket system link on the e-mail flyer.
Any problems please e-mail the Regional CPD Co-ordinator James Sizer
firstname.lastname@example.org or Regional Committee Member and Norwich Centre of Excellence CPD Co-ordinator Darren Burrell email@example.com
Darren Burrell MRICS C.Build E FCABE
15 November 2018