Approved Document C
The first set of national building standards was introduced in 1965. Now known as the building regulations, they set out:
- What qualifies as 'building work' and so fall under the control of the regulations.
- What types of buildings are exempt.
- The notification procedures that must be followed when starting, carrying out, and completing building work.
- Requirements for specific aspects of building design and construction.
The 'approved documents' provide guidance for how the building regulations can be satisfied in common building situations. There is no obligation to adopt the solutions presented in the approved documents, the building regulations can be satisfied in other ways.
Approved Document C: Site preparation and resistance to contaminants and moisture, was last published in 2013.
It covers the weather-tightness and water-tightness of buildings, subsoil drainage, site preparation, and measures to deal with contaminated land, radon, methane, and other site related hazardous and dangerous substances.
In terms of resistance to moisture, the regulations state that the building should be protected from harmful effects caused by:
- Ground moisture.
- Precipitation including wind-driven spray.
- Interstitial and surface condensation.
- Spillage of water from, or associated with, sanitary fittings or fixed appliances.
It defines a ‘contaminant’ as ‘any substance which is or may become harmful to persons or buildings, including substances which are corrosive, explosive, flammable, radioactive or toxic’; and lists examples of sites likely to contain contaminants, including:
- Animal and animal products processing works.
- Asbestos works.
- Ceramics and asphalt manufacturing works.
- Chemical works.
- Dockyards and dockland.
- Gas works.
- Landfill and other waste disposal sites.
- Oil storage and distribution sites.
- Power stations.
- Scrap yards.
- Sewage works.
- Texile and dye works.
The content of the Approved Document includes:
- Section 1: Clearance or treatment of unsuitable material – This includes guidance on various site investigation measures and types of unsuitable material.
- Section 2: Resistance to contaminants – This includes risk assessment and remedial guidance on solid and liquid contaminants, methane and other gases from the ground, and radon.
- Section 3: Subsoil drainage.
- Section 4: Floors – This includes guidance and technical solutions for ground supported floors, suspended timber ground floors, suspended concrete ground floors, floors exposed from below, and resistance to surface condensation and mould growth.
- Section 5: Walls – This includes guidance and technical solutions for internal and external walls (moisture from the ground), external walls (moisture from outside), solid external walls, cavity external walls, cavity insulation, framed external walls, cracking of external walls, impervious cladding systems, joints between doors and windows, door thresholds, and resistance of external walls to damage from interstitial condensation, surface condensation and mould growth.
- Section 6: Roofs – This includes guidance and technical solutions for roof resistance to damage from moisture from outside, interstitial condensation, surface condensation and mould growth.
[edit] Related articles on Designing Buildings
- Approved documents.
- Approved Document D.
- Approved Document F.
- Approved Document H.
- Brownfield land.
- Building Regulations.
- Condensation.
- Contaminated land.
- Cover systems for land regeneration - thickness of cover systems for contaminated land (BR465).
- Deleterious materials.
- Ground conditions.
- Hazardous substances.
- Mould growth.
- Radon.
- Radon: Guidance on protective measures for new buildings BR 211.
- Types of damp-proof courses.
Featured articles and news
The Architectural Technology podcast: Where it's AT
Catch up for free, subscribe and share with your network.
The Association of Consultant Architects recap
A reintroduction and recap of ACA President; Patrick Inglis' Autumn update.
The Home Energy Model and its wrappers
From SAP to HEM, EPC for MEES and FHS assessment wrappers.
Future Homes Standard Essentials launched
Future Homes Hub launches new campaign to help sector prepare for the implementation of new building standards.
Building Safety recap February, 2026
Our regular run-down of key building safety related events of the month.
Planning reform: draft NPPF and industry responses.
Last chance to comment on proposed changes to the NPPF.
A Regency palace of colour and sensation. Book review.
Delayed, derailed and devalued
How the UK’s planning crisis is undermining British manufacturing.
How much does it cost to build a house?
A brief run down of key considerations from a London based practice.
The need for a National construction careers campaign
Highlighted by CIOB to cut unemployment, reduce skills gap and deliver on housing and infrastructure ambitions.
AI-Driven automation; reducing time, enhancing compliance
Sustainability; not just compliance but rethinking design, material selection, and the supply chains to support them.
Climate Resilience and Adaptation In the Built Environment
New CIOB Technical Information Sheet by Colin Booth, Professor of Smart and Sustainable Infrastructure.
Turning Enquiries into Profitable Construction Projects
Founder of Develop Coaching and author of Building Your Future; Greg Wilkes shares his insights.
IHBC Signpost: Poetry from concrete
Scotland’s fascinating historic concrete and brutalist architecture with the Engine Shed.
Demonstrating that apprenticeships work for business, people and Scotland’s economy.
Scottish parents prioritise construction and apprenticeships
CIOB data released for Scottish Apprenticeship Week shows construction as top potential career path.
From a Green to a White Paper and the proposal of a General Safety Requirement for construction products.
Creativity, conservation and craft at Barley Studio. Book review.
The challenge as PFI agreements come to an end
How construction deals with inherited assets built under long-term contracts.
Skills plan for engineering and building services
Comprehensive industry report highlights persistent skills challenges across the sector.
Choosing the right design team for a D&B Contract
An architect explains the nature and needs of working within this common procurement route.
Statement from the Interim Chief Construction Advisor
Thouria Istephan; Architect and inquiry panel member outlines ongoing work, priorities and next steps.