Architecture Public knowledge base

Reviewed 25.10.2026England focus

Jasmine Gokmen
In forceStructure & Site

Approved Document C: Site preparation and resistance to contaminants and moisture

Contaminants, groundwater and weathertightness

Addresses site preparation, resistance to contaminants such as radon, methane and volatile organic compounds, and resistance to moisture penetration.

Also known as: AD C, Approved Document C

Jurisdiction
England
Document type
Statutory guidance
Edition
2013 edition
Source updated
3 September 2013
Applies from
—
Topic
Structure & Site

Key requirements

  • Requires a site investigation where contaminants may be present.
  • Covers radon, methane, landfill gas and volatile organic compounds.
  • Guidance on damp-proof courses, membranes, floors, walls and basements.
  • Weathertight construction and resistance to ground moisture are central.

Performance at a glance

Contaminants
Radon, methane, VOCs
Moisture
DPC / DPM and weathertight details

Applies to

New buildings, extensions and work affecting the building envelope in England.

Official source

GOV.UK — Approved Document C

Open official source

Related records

Part A · StructurePart D · Toxic substancesPart 7 · Materials and workmanship

Reviewed 25 October 2026. This summary is an editorial reference, not legal advice. Check the current official text and confirm the approach with building control before relying on it. Browse all 35 records.