Frequently Asked Questions


A. The Ground report provides a property-specific ground stability risk assessment from all mining, and natural ground stability hazards. It includes our CON29M coal mining report as standard and provides an assessment from over 55 different minerals mined across the country, including tin, lead, limestone, China clay, Cheshire brine, chalk and many more.

A. An ‘MEIR’ is a ‘Mine Entry Interpretive Report’. MEIR’s are required when a coal mine entry is identified within 20 metres of a Site. It provides a focused assessment of the risk of instability posed by a mine entry by calculating its ‘Zone of Influence’ (the surface area that could be impacted by mine entry instability) and considering other factors such as record accuracy, building locations and whether the mine entry has been treated. Terrafirma provide an MEIR free of charge within their CON29M and Ground reports.

A. ‘Zone of Influence’, or often abbreviated to ‘ZOI’, is the area at the surface that a mine entry may affect should it become unstable in future. The ‘ZOI’ of a mine entry is influenced by a number of factors, including the mine entry diameter, the thickness of superficial deposits above the mine entry and the geological properties of those superficial deposits. The experts at Terrafirma have calculated the ‘ZOI’ for all mine entries recorded by the Coal Authority (over 173,500) and utilise this information within any included Mine Entry Interpretive Report to provide a detailed and accurate assessment of the likelihood of adverse impact by a mine entry to a Site.

A. Terrafirma offer a free of charge ‘Hazard Alert’ service. This is a report recommendation service, and simply aims to identify whether a property is within an area of known mining and/or natural ground hazards. The ‘Hazard Alert’ will detail which Terrafirma report is most appropriate for the Site, in order to provide a Site-specific assessment of any such hazards to determine the risk of ground-instability.

A. The loss of value insurance, which comes with any Terrafirma Coal, CON29M and Ground report, is an insurance policy that offers cover to any report holder in the event that a future change in Coal Authority data (be it relating to coal or a non-coal mineral within their database), as revealed within a subsequent Report, has a detrimental impact to the market value of the property. This policy provides cover for any loss in market value up to £100,000. Terms of this policy can be found at the back of reports to which they are supplied.

A. If your report has been given a ‘Further Action’ outcome, this is where Terrafirma have identified a potentially significant risk of ground instability to the Site and recommend further actions be undertaken, prior to purchase, for further assurances regarding the condition and security of the property. On page 2 of the report, under the section ‘Next Steps’, you will find our recommendations.

If a TerraSearch Action report has been recommended, this is where Terrafirma believe further desk-study reporting will better determine the risk of instability to a Site. Please contact Terrafirma by phone or email for a quote and estimated return times for this report. Please note that this report is only available to order when explicitly recommended within a Terrafirma Coal, Coal Extra, CON29M or Ground report.

If a survey of the property has been recommended, this is where Terrafirma believe past ground movement may have occurred and a visual survey will identify whether any significant structural defects in the fabric of the property/grounds are present that may be indicative of past or ongoing ground movement. This is unfortunately not a service that Terrafirma can provide but instead it is advised to contact a suitably qualified surveyor/structural engineer for a quote and for further information.

If a walkover survey, mining investigation or a ground investigation has been recommended, this is where Terrafirma have identified evidence of hazardous mine workings and/or hazardous natural ground conditions which require on-site investigation to determine their extent, condition and potential for future instability. These are unfortunately not services that Terrafirma provide. Instead, it is recommended to contact a suitably qualified geotechnical engineer or geotechnical consultancy for quotes and further information.

A. Terrafirma will provide an Advisory for clay subsidence when Terrafirma identify an enhanced risk of clay-related subsidence affecting the Site. Clays are a naturally occurring material and some clays can shrink and swell dependent on the moisture content within the soil. While movements on a day-to-day timeframe would be minimal, seasonal ground movements can occur and result in more significant movements (e.g. a hot, dry summer following a wet winter). Should these seasonal ground movements occur, they can affect and damage overlying property over time. Furthermore, the presence of trees and their root systems can result in greater movements within their vicinity.

Terrafirma complete their assessment using remotely accessible data from Cranfield University, BlueSky tree mapping and additional providers. The information available to us indicates clays susceptible to shrink-swell may be present beneath the Site, however, this does not confirm their presence or that ground movements will/have occurred. Our advice is to obtain a survey of the property to identify any defects within the structural fabric of the property that may be indicative of past seasonal ground movements. Should defects be identified, it is advised to seek further expert advice from the surveyor and to assess the need for structural repairs/mitigation measures. Should no defects be identified, this does not fully discount the possibility of movements occurring in future and therefore it is important to ensure appropriate buildings insurance, that covers the risk of subsidence, is obtained for the property. Please note in these areas insurance premiums may be higher than average.

It is worth noting that these shrink-swell ground conditions are often considered at the time of development. If the property being purchased is a plot/new build, further assurances may be available from the developer regarding the consideration and mitigation of subsidence risk from clay soils.

A. Terrafirma’s Ground report covers all mining hazards, including tin mining. Mining in Cornwall, particularly for metalliferous minerals (such as tin, copper, silver, etc.) is renowned for having been incredibly complex and extensive within the region. This is why Terrafirma are partnered with Cornwall Consultants, mining search and investigation specialists based in Cornwall, who complete the ‘All Other Mining’ section of the Terrafirma Ground report for any Ground report order received within known Cornwall mining areas. This enables users of the Ground report to benefit from Cornwall Consultants’ 30 years of experience and knowledge in mining-risk assessments, at no additional cost.

A. All current Terrafirma reports are desk-study assessments only, compiled using our extensive archive and database of remotely accessible data. The reports, or our services, do not involve or extend to any on-Site inspections or surveys.


A. Typically orders for our reports are placed by the conveyancer, through their preferred search provider, acting on the behalf of the prospective purchaser. However, we can take direct instruction if you order via email. To do this, please email our team ([email protected]) and they will guide you on how to order a report and can advise on which report best suits your property.

A. Terrafirma’s coal reports take up to 2 working days for return, Terrafirma’s Ground report can take up to 4 working days for return. However, 90% of all reports are returned within 24 hours of order.

A. Terrafirma do offer an expedite service, this can be chosen for any coal or Ground report order and it guarantees return within 24 hours of order, or next working day. This service costs an additional 20% and can be selected when ordering a report, or activated by phoning or emailing our team.

A. Terrafirma offer a free, no questions asked cancellation policy for any order placed within the last 24 hours, or previous working day. If an order had been placed on an incorrect property or requires an amended address, Terrafirma offer a free cancel/replace policy whereby a new replacement order can be placed free of charge, provided that the original order was placed within the preceding 28 days. To check if an order can be cancelled, or is eligible for a cancel/replace, please either phone or email the team.

A. Terrafirma offer a free report recommendation service, known as the Terrafirma Hazard Alert, to let you know whether a report is needed, and if so which report is most suitable for the property. This service can be accessed through your preferred search provider in their search alerts, through an account on our website or by phoning or emailing our team.

A. For further information on our reports and their recommended retail prices, please go to our reports page. If you are a partnered reseller, please consult your latest reseller agreement or contact your account manager.

A. If you would like to create an account with us to both use our Hazard Alert service and to order reports, please fill in the request account form. However, if you are only seeking to order a one-off report, please contact our team by phone or email to ask how to place an order. If you currently order reports through a preferred search provider, we are partnered with most major resellers and a list of our partners can be found here.

Additional Information

Fracking, or unconventional shale-gas extraction, is a method of gas recovery that involves high pressure fluid injection (defined by set threshold rates in the UK) into shale rocks. This injection opens cracks within the shale and ‘stimulates’ a flow allowing the gas to be collected and harvested at the surface. Operations tend to occur via drilling sites at the surface, with the main drilling and injections then occurring horizontally, generally at depths of over 1km.

In November 2019, following seismic events at the Preston New Road fracking Site in Lancashire, the UK Government ended its support for fracking operations in the UK. Fracking operations will not be allowed to proceed in the UK, unless “compelling new evidence of its safety and minimal impact to residents is provided”. It is therefore not impossible for fracking operations to resume in future, or for exploration activities to occur in the interim, but for the time-being fracking operations have ceased. Further information regarding the Government’s position can be found here:

In the event fracking does occur in future, fracking operations may impact the quiet enjoyment and the value of a Site. Should you like further information regarding shale-gas (fracking) extraction please visit: It is important to note that any decisions on fracking activities in the UK is subject to the appropriate planning process as outlined within the National Planning Policy Framework (NPPF). Further information can be found at:

Furthermore, all fracking operations in the UK are also subject to the appropriate regulation by regulators such as the OGA, DECC, Mineral Planning Authority (MPA) Environment Agency (EA) and the Health and Safety Executive (HSE).

Radon is a naturally occurring, radioactive gas that forms from the breakdown of uranium, which can be found naturally in all rocks and soils. Certain rock types and geology can contain greater amounts of uranium and this results in higher radon concentrations in certain parts of the country. As it is radioactive, radon decays and emits radiation which can be a risk to health when exposed to it in high enough concentrations. The average concentration in homes is estimated to be 20 Bq m-3 (bequerels per cubic metre of air) yet levels up to 100 Bq m-3 are considered relatively low risk to health and this is therefore the ‘target level’ of radon for homes across the country. If radon concentrations are at or above 200 Bq m-3 (known as the ‘Action Level’), it will be advised to take measures to reduce radon levels within the building.

As radon gas is a potential health hazard when present in high concentrations, it is now standard practice for radon ‘searches’ to be completed within searches completed during the conveyancing process. These searches initially check to see if a property is within a ‘radon Affected Area’. The UK Health Security Agency defines a ‘radon Affected Area’ as those where over 1% of properties/buildings have radon concentrations at or above the ‘Action Level’ of 200 Bq m-3. If a property is within a ‘radon Affected Area’, it is then advised to obtain a physical test of radon within the building. Testing for radon is simple and relatively inexpensive and a measurement kit can be purchased through the UK Health Security Agency at Further information regarding radon can be found on the UK radon website here

Download the Coal Authority statutory duties here

Download Coastal Erosion here

Download Mineshafts here

2021 Report Updates

CON29M – Not just about coal anymore!
From October 18th, Terrafirma’s CON29M report will provide an assessment and advice relating to non-coal mining hazards, within Coal Authority data. We’re adding property specific risk assessment in line with Terrafirma’s expert reporting and search methodologies. Conveyancers who choose a Terrafirma CON29M will receive clear identification of when a property is within influence or at risk of mining-related instability from non-coal workings. It will also alert all parties of the implications of non-coal mining workings affecting the property, most notably that the terms of the Coal Mining Subsidence Act 1991 may not apply.

Ground Report
Following an in-depth technical review that involved several senior geologists, scientists and engineers, Terrafirma have enhanced the assessment techniques, hazard-specific advice and recommendations for natural ground perils. Where necessary, the enhanced Ground Report section provides property-specific advice and recommendations for ground conditions that can pose a notable risk to property. Hazard-specific advice is provided for those interested in the future development of the site, which can be passed along to a builder/developer to ensure the ground conditions are appropriately considered.

The use of satellite data to identify ground movement in the wider area surrounding a property has also been reviewed and upgraded, offering better interpretation to evidence recorded movements relevant to the property in question.

The Ground Report will also feature a redesigned front page to improve report clarity and allow better ‘at-a-glance’ review of report and its results. As part of the redesign, a Terrafirma ‘Quality Assurance Stamp’, has been added, clearly demonstrating the expertise embedded within every report. ‘

Site plans, which allow conveyancers and homebuyers to visualise the potentially affected areas from natural ground perils, clay subsidence and mining hazards, have been visually enhanced for improved report usability.

A. The updated CON29M will assess any non-coal mining hazards that are recorded within Coal Authority data (within the Coal Mining Reporting Area). There unfortunately exists many areas, mine workings and mining features for non-coal minerals outside of the Coal Authority data and coal reporting area and so it is important to consider their potential presence when choosing the best report for a property. For an assessment of any coal & non-coal mining hazards, using data from To help you find out which report is best for a property, you can use Terrafirma’s free Hazard Alert service. This service is available through Terrafirma’s partnered resellers, an account on our website or by asking the team by phone or email.