Approved Document C Frequently Asked Questions – UK Building Regulations Guide
The Approved Document C Frequently Asked Questions is a technical guidance document issued by the Department for Communities and Local Government in the United Kingdom. It provides clarifications on the application of Building Regulations concerning Site preparation and resistance to contaminants and moisture. The document serves as a supplementary resource for the Approved Document C 2004 edition, which incorporates amendments made in 2010 and 2013.
The scope of this guidance covers common professional inquiries related to residential extensions, the installation of moisture barriers, and the management of environmental risks such as soil gases and flooding. It outlines the specific technical standards for damp proof courses (DPC), provides directions for identifying radon-affected areas, and clarifies the regulatory boundaries between building control and planning approval regarding flood mitigation measures. The text references several external authorities, including the British Standards Institution (BSI) and the Building Control Authority.
The information is structured into four primary categories: Information on extensions, Chemical damp proof course, Areas affected by Radon, and Flood mitigation. Each section provides specific regulatory interpretations and directs practitioners to relevant standards and reporting services for compliance and site assessment.
Documentation and Approval for Extensions
Property owners and professionals seeking evidence of Building Regulations approval or planning permission for existing extensions must contact local administrative bodies. The document clarifies that specific records for recent dwellings are maintained by designated authorities.
- Local Authority Planning Office: Maintains records of planning permissions sought and granted for property extensions.
- Building Control Authority: Responsible for holding documentation regarding the final inspection and regulatory compliance of building works.
Standards for Damp Proof Courses (DPC)
For new extensions to existing properties, the guidance specifies strict material and installation requirements to prevent the passage of moisture. Even if an original structure uses a chemical damp proof course, new building works must adhere to standard physical barriers.
- Minimum Height: The damp proof course must be installed at least 150mm above ground level.
- Approved Materials: Suitable materials include impervious sheet material, engineering brick, or slates set in suitable cement mortar.
- Reference Standard PD 6697:2010: Recommendations for the design of masonry structures to BS EN 1996-1-1 and BS EN 1996-2.
- Reference Standard BS 5628 Part 3:2005: Code of practice for the use of masonry, covering materials, components, design, and workmanship.
Radon Protection and Risk Assessment
The document addresses the identification of geographical locations that require radon protection for both domestic and workplace buildings. It points to established reporting services that provide site-specific risk assessments.
- UK Radon Service: The primary resource for obtaining radon risk reports for small domestic buildings and extensions with an existing postal address (www.UKradon.org).
- Geographical Identification: Protection measures are mandatory in areas where radon gas levels exceed specified thresholds as identified in regional risk reports.
Flood Mitigation and Building Regulations
Clarification is provided regarding the scope of Building Regulations in relation to flood risk. While site preparation is regulated, specific flood mitigation measures designed to keep water out of a building or facilitate quick re-occupation are treated differently.
- Regulatory Scope: Flood mitigation is not a matter covered by Building Regulations; however, it is frequently included as a condition in planning approval.
- BS 85500: The core standard for flood resistant and resilient construction, providing guidance on improving the flood performance of buildings.
Frequently Asked Questions
Where can I find records of Building Regulations approval for a rear extension?
Records for recent extensions to dwellings are held by the Local Authority Planning Office and the Building Control Authority.
What is the minimum required height for a damp proof course in an extension?
The damp proof course in extension walls must be placed at least 150mm above ground level.
Are chemical damp proof courses permitted for new extensions?
The guidance specifies the use of impervious sheet material, engineering brick, or slates; it does not list chemical DPC as the standard for new ground-level extension walls.
Which British Standard covers the design of masonry structures for moisture resistance?
PD 6697:2010 provides recommendations for the design of masonry structures regarding moisture resistance.
Where can property owners find radon risk reports for existing properties?
Radon risk reports can be obtained from the UK radon website at www.UKradon.org for domestic and workplace buildings.
Does Approved Document C cover flood mitigation measures?
No, flood mitigation measures to keep water out or allow quick re-occupation are not covered by Building Regulations, though they may be required by planning approval.
What is the standard for flood resistant and resilient construction?
Advice on flood-resilient construction is found in BS 85500, which can be obtained through the British Standards Institution.
