Building Regulations, Approved Documents – Part C Site preparation and resistance to contaminants and moisture

An overview of Building Regulations, Approved Documents – Part C Site preparation and resistance to contaminants and moisture

Part C is about ensuring that the site for new buildings is prepared in a manner that will promote resistance to contaminants and moisture for the structure that is to be built on the site.

As of the date of writing, Part C was last revised in 2010 as a result of the Building Regulations 2010.

There are a number of subjects that fall within this part of the regulations. These include weather and water tightness, drainage and measures to deal with contamination and hazardous substances such as radon and methane.

Part C Site preparation and resistance to contaminants and moisture contain the following high-level requirements:

  • C1 Preparation of site and resistance to contaminants
  • C2 Resistance to moisture

There are three key aspects in the preparation of the site – that the site to be covered by the building & associated land is free from materials that might damage the building such as pre-existing foundations or vegetable matter, be free of contaminants and provide adequate drainage.

The regulations provide helpful information related to undertaking a risk assessment of contaminants and a high-level overview of some of the remedial measures that are available.

One potential contaminant that we all need to consider when building is radon. It’s not a major issue in most of the UK; the south-west is the area most at risk, but one we all need to consider. Start on the British Geological Survey website.

The second part of the regulation, that dedicated to discussion of resistance to moisture contains useful information related to site surveying, subsoil drainage and the construction of resistant floors, walls & roofs. A useful map confirms what we knew all along, that most of Wales is exposed to very severe driving rain. What would we in Wales do without the blessed rain…?

The myth(?) of rising damp…

…and Rigsby is not in sight…

I was watching an episode of QI the other night when the ‘myth’ of rising damp – or rather, the lack of evidence for the existence of rising damp as a ‘real’ issue, was mentioned. This wasn’t something I’d ever heard of and some further web-based research makes for some interesting reading…

There’s plenty of information on the subject across the web which Google will find for you, I’ll provide a link to one article that demonstrates the venom of the argument between ‘believers’ and ‘non-believers’. The Architects Journal carries a post, which you can access by searching in Google with this text – ‘architects journal’ Rising damp is a myth – make sure you read through the readers comments. [architectsjournal.co.uk doesn’t allow deep links to articles, just to the home page – typical closed thinking of the kind I’ve seen a lot of from the architectural community recently..]

From my layman’s reading, it appears that there is little proof that water will rise through a ‘normally’ constructed wall by capillary action and therefore little basis for expecting damp to rise up a wall that hasn’t been protected in any of the normal ways (usually a damp-proof-course). It is often the case that what is diagnosed as rising damp is actually condensation caused by poor heating and ventilation or damp penetrating from exterior raised ground levels or leaking water pipes. As usual with a complex issue, this isn’t as cut-and-dried (sorry!) as some people would like. Personally, I tend toward the middle ground – that rising damp is rare, often misdiagnosed, but can occur given certain specific sets of circumstances.

Additionally, I’ve always been dubious of the usefulness of chemically injected damp proof courses, especially when applied to rubble filled masonry walls like those of the barn and the arguments around this issue confirm my doubts.

…So perhaps, under certain circumstances, rising damp does exist, despite what they say on QI…