Digging conservatory foundations in a former coalfield can meet old shafts, shallow workings or mine gas. The Mining Remediation Authority publishes guidance for home extensions, and it names conservatories specifically. Its guidance covers development high risk areas across England, Scotland and Wales; the separate planning and building control systems of each nation are not detailed here. This guide is general information, not engineering, legal or planning advice.

Checking whether your home is in a high risk area

The guidance says mining risks must be checked if a home is in a development high risk area, which includes many former coal mining areas across England, Scotland and Wales. It points to a free online map showing whether a property is in a high risk area, along with recorded mining information. Covered improvements include house extensions, conservatories, garages and outbuildings, driveways and patios, and garden structures.

The guidance adds that many home improvements in these areas do not need planning permission but could still require building regulations approval, and that mining risks should be considered for both. Whether a conservatory is exempt from the Building Regulations is a separate question, covered in this site’s guide to the exemption for conservatories.

Who is responsible

The homeowner is responsible for making sure the development is safe and stable, according to the guidance. The Mining Remediation Authority does not sign off or approve householder proposals and will not carry out investigatory or remedial safety work for the homeowner. It also says it is not consulted on householder developments as part of the planning process, but the local planning authority or building control body could still ask the homeowner to prove the development will be safe. The guidance recommends considering the risks at the earliest stage, ideally before a planning or building regulations application is submitted.

The hazards to consider

The listed hazards are mine entries (old shafts and tunnels), shallow mine workings, coal seam outcrops at the surface, opencast mining sites, ground fissures and break lines, mine gas and mine water. All must be given appropriate consideration in the proposals. On mine entries, the guidance says to avoid building over or close to them, and that building over or within the influencing distance of a mine entry can be dangerous. Its planning guidance adds that the Authority’s policy is that building over or close to mine entries should be avoided wherever possible, even after they have been capped.

Mine gas should be assessed by a qualified specialist where there is any risk, and the guidance calls a gas risk assessment prudent where a source, a pathway and a receptor could be present. The Authority does not carry out gas risk assessments.

Mining reports and risk assessments

The guidance distinguishes three products. A CON29M report gives basic conveyancing information for house purchases and should not be used to inform a coal mining risk assessment for development. A consultants’ report gives detailed technical information. A coal mining risk assessment is a professional assessment of the risks to the specific development.

The local planning authority or building control body can request a coal mining risk assessment if they consider it necessary. It must be prepared by a qualified professional who reviews all available information for the site. Separate planning guidance says householder development is on the list of application types for which the Authority, as statutory consultee, does not require one, while noting that a planning authority may consider other cases. See the guide to conservatory foundations for ground conditions more generally.

When a separate permit is needed

A permit from the Mining Remediation Authority is required before starting work if the development could disturb or enter coal seams, or affect historical coal mine workings or mine entries. The guidance says this includes digging foundations or putting in new drainage that could intersect the Authority’s property. Removing any coal during building work also needs an incidental coal agreement. These requirements exist alongside, not instead of, planning and building control.

Getting professional advice and reporting finds

The guidance recommends advice from someone who understands ground stability and mining hazards, with qualifications in geology, geotechnical engineering, mining engineering or structural engineering, and membership of a relevant professional body such as the Geological Society or the Institution of Civil Engineers. If mining features are discovered during work, the guidance says to call the Authority’s 24-hour hazard line immediately. Building control arrangements are explained in choosing building control.

FAQs

Does a conservatory in a coal mining area still need mining checks if it is permitted development?

The guidance says many improvements in high risk areas do not need planning permission but could still need building regulations approval, and mining risks should be considered for both.

Will the Mining Remediation Authority approve my conservatory?

No. The guidance says it does not sign off or approve householder development proposals.

Is a CON29M search enough?

The guidance says a CON29M report should not be used to inform a coal mining risk assessment for development.

When is a permit needed?

Before starting work if the development could disturb or enter coal seams or affect historical workings or mine entries, including digging foundations or drainage that intersects the Authority’s property.

The bottom line

In a former coal mining area, a conservatory carries mining considerations even where it needs no planning permission. The Mining Remediation Authority says the homeowner is responsible for safety and stability, that a permit is needed for work that could affect coal seams or mine workings, and that building over mine entries should be avoided. Checking the high risk area map and taking professional advice before design and foundation work is the guidance’s starting point.

Sources

This guide draws on the following sources, current as of 25 September 2026:

• GOV.UK, Mining Remediation Authority, “Home extensions and improvements in former coal mining areas”
• GOV.UK, Mining Remediation Authority, “Planning applications and Coal Mining Risk Assessments”

Related guides

Compare Conservatories is an independent guide. We may earn a fee from some links; this never affects what we write. This article is general information, not legal or planning advice on any specific property — always confirm requirements directly with your local planning authority.