Check historical mining before buying land

Altbergbau is a subsurface risk

Altbergbau covers disused or abandoned mine workings whose recorded position, support and backfilling do not always align with the current cadastral map. A shaft may lie beneath later construction, a tunnel may carry water, and a mined void may affect the surface only after a long delay. A purchase review therefore cannot rely on the house age or a general statement in the sales brochure. The relevant reference is the Gemarkung, Flurstück (cadastral parcel) and intended use. Building, adding a basement, drilling for a heat pump or laying a service requires a different depth of investigation from an undeveloped open area. The Bundesberggesetz, the Federal Mining Act regulates mining supervision and mining-damage law, but it does not replace a local file search or a site-specific report. Further investigation remains necessary even where existing buildings appear stable, because later movement or water paths are not excluded.

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Distinguish shafts, tunnels and mined voids

A shaft is an artificial opening to the surface or to deeper mine workings. Its safety depends on its position, construction, filling and later interventions. A Stollen, a predominantly horizontal tunnel, may pass below a plot without any visible surface sign. Mined voids form where the extracted deposit was removed; their stability depends on the rock mass, support and water flow. Spoil heaps, Pingen and Tagesbrüche are visible clues, but they do not prove the full extent of the underground works. Old mine plans can use different coordinate systems, scales or uncertain local references. The BGR Geoportal helps classify geological processes; the competent Bergbehörde must assess the actual mine location from its records. A positive map indication therefore leads to further investigation, not automatically to a building ban.

Which office carries out mining supervision

Under § 69 BBergG, mining supervision lies with the competent authority. The state office that responds depends on the property and the organisation under state law. The municipality can provide building files, the Bebauungsplan (binding local development plan) and local information, but it does not replace the Bergbehörde for every record of underground mining. State law and the actual subsurface must be assessed separately. State law determines the chain of authorities and the form of the response. A reliable request should identify the Flurstück, Gemarkung, site plan, intended use and precise question. For a built plot, also state the construction year, basement, extensions and known cracks. A reply with an file number and processing status can later be matched to the purchase contract and report. The state table lists the specialist offices recorded for all sixteen states. It helps locate the correct entry point; it does not promise that the individual Flurstück is risk-free.

Read an Aufmerksamkeitsgebiet correctly

An Aufmerksamkeitsgebiet marks an area where former mining or geological evidence triggers a deeper review. The term does not identify a settled cause of damage and is not a general ban on every project. Within such an area, a plot without relevant workings may stand next to land with Tagesöffnungen, openings reaching the surface. Conversely, an individual plot outside a broad depiction may have historical traces visible only in an archive or mine plan. The decisive matters are the map version, the area of influence and the proposed earthworks. Ask the Bergbehörde whether the Flurstück lies in an Aufmerksamkeitsgebiet, which records support that assessment and whether technical investigation is required. Also compare planning documents and earlier building files at the municipality. A coloured area map is a search tool. It becomes commercially usable evidence only after a Flurstück review, file response and geotechnical assessment.

Mining damage or ordinary settlement

Cracks, tilting and uneven settlement can have several causes, including changing soil layers, fill, drying soils, groundwater changes, inadequate foundations or nearby construction. Bergschaden, mining damage, requires a connection with mining operations and an effect relevant under mining-damage law. The visible form alone does not decide the issue. A crack log should record its course, width, position, date and change; level surveys can show movement over time. Historical maps and the building file can show whether the foundation was already problematic before the suspected movement. The report must therefore distinguish cause, alternative causes and the load imposed by the planned use. § 114 BBergG defines the starting point for mining-damage law, while an ordinary ground defect may be governed by different rules. Proximity to a former mine is not proof.

The statutory presumption under § 120 BBergG

§ 120 BBergG creates a statutory presumption for certain damage within the area of influence of underground exploration or extraction. It includes subsidence, heave, compression, tension, ground cracks and vibration where the type of damage can be mining damage. The presumption is not a blanket claim for every crack. It applies only when the statutory conditions are met and may fall away where an obvious construction defect, unlawful construction use, natural geological or hydrological causes, or a third-party intervention can be established. Anyone relying on the presumption must document the damage and its spatial connection objectively. Building permits and inspection records may also be required for damage to structures. The rule assists with allocating the burden of explanation, but it does not replace defining the area of influence or examining the actual damage pattern.

Mine water and rising water levels

After closure, the hydraulic balance of a mine can change. Water may rise in shafts and galleries, emerge along fault zones or affect the groundwater level. A property may then face dampness, corrosion, gas release, uplift or changed bearing capacity. The bare statement that a mine is closed answers none of these questions. The Bergbehörde may hold information on water management, securing works and known emergence points; the Wasserbehörde assesses water-law consequences. For a basement, underground garage or borehole, the report must describe planned depth, waterproofing, uplift safety and possible drainage. Pumps and permanent dewatering systems also require separate legal and technical review. The Wasserhaushaltsgesetz, the Federal Water Act provides the federal framework for water bodies and groundwater. A historical water-level statement must not be treated as a current forecast if operations, climate or development have changed.

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Land register, mining-damage waiver and priority

A Bergschadenverzicht, a mining-damage waiver, may appear in the Grundbuch, in a consent document or in older purchase papers. It is neither automatic evidence of damage nor a release from every investigation. The important points are the beneficiary and burdened right-holder, affected areas, types of damage covered, period of application and any consideration. Read the instrument referred to by the land-register entry. Under § 873 BGB and § 19 GBO, a land-register change depends on agreement, registration and consent. A private declaration outside the register may have different content and evidential weight. Obtain all attachments before notarisation and establish whether the waiver continues against the buyer. The financing bank must know whether a claim is excluded, limited or difficult to enforce.

What a geotechnical report must do

A general Baugrundgutachten, a ground investigation report, is not automatically an Altbergbau investigation. The commission must name the actual structure, foundation, earthworks and known mining indications. It should evaluate mine plans, maps, drilling data and building files, describe the geological model and search for voids and Tagesöffnungen. Depending on the findings, historical research, drilling, geophysical methods, trial pits or technical stabilisation may be required. The report should disclose assumptions and limits: unexamined areas must not be described as free of voids. The structural engineer needs conclusions on differential settlement, bearing capacity, water, gas and possible foundation strengthening. Request a plan showing investigation areas, coordinates and findings. A dependable report separates observed facts, model assumptions, risks and recommended measures. It should also say whether the investigation is adequate for the planned building or must be redone after a change of use.

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How to ask the Bergamt

The request should not merely ask whether Altbergbau exists. Identify the property by Gemarkung, Flur and Flurstück, attach a site plan, mark the building area and describe basements, foundations, services, drilling or fill. Ask about shafts, tunnels, mined areas, spoil heaps, Tagesbrüche, securing records, known areas of influence and current safety measures. Request the file number, map version, source coverage and a statement on whether technical investigation or the involvement of another authority is required. For a purchase review, the authority should be able to see whether the request covers the whole Flurstück or only part of it. Put a telephone response in the file as a call note, but do not treat it as a written answer. The Bundesportal entry on municipal provision of building land may help with the first step; the competent office remains the one designated under state law. Answer follow-up questions fully so the review does not rest on an unclear location.

Purchase contract and notarial appointment

Before the notarial appointment, the parties must know which findings exist and which questions remain open. Under § 311b BGB, a land purchase requires notarisation. The contract should contain traceable information about the authority response, report, land-register entry and intended use, not unchecked promises. If a report is still missing, state clearly whether the parties intend a right to withdraw, a suspensive condition, a price adjustment or an allocation of costs. A general exclusion of defects does not answer whether the seller must disclose known records. Check the exact Flurstück designation and attachments in the draft. Also establish whether a Bergschadenverzicht, easement or security agreement affects financing priority. The Bundesnotarkammer information service explains the notarial role, but does not replace review of the actual contract by the parties and advisers.

Costs, deadlines and construction sequence

Altbergbau can affect the programme long before the first excavation. Start with the file response and map review, then technical investigation, and only afterwards decide on foundation, stabilisation or a change of plan. The programme should allow for the authority's processing time, commissioning the specialist report, access to neighbouring land, monitoring periods and possible follow-up work. Costs are not limited to the report. Surveying, drilling, geophysics, filling, stabilisation, dewatering, structural design, permits and construction supervision may follow. A buyer who looks only at the purchase price underestimates the risk. Request separate quotations for research, investigation and remedial work, and ask for unexplained items to be broken down. State law and local by-laws may affect fees or competence; a general statement does not apply to every procedure. The Kostenordnung für Gerichte und Notare, the Court and Notary Costs Act applies only within its statutory scope. Set the construction start only after the competent specialist offices and technical solution are documented in writing.

File for the individual Flurstück

Organise the documents so that every statement refers to the same area. The file should contain the current land-register extract and instruments, cadastral extract, project site plan, Bergbehörde response, historical maps, building file, crack log and geotechnical report. Add the date, file number, case officer, map basis and spatial review area. A later change to the basement, foundation or service route can alter the technical assessment and must be reported. Mark which areas were investigated and which remained open because of services, buildings or access problems. The municipality remains responsible for the Bebauungsplan and building permit; the Bergbehörde assesses mining matters, and the Wasserbehörde addresses groundwater questions. State law distributes these tasks differently. A report limited to the house footprint says nothing about a new garage or deep borehole. Use ground investigation reports, land register and ALKIS and Bebauungsplan and buildability for the adjacent checks.

Clarify the subsurface before deciding to buy. A land analysis brings together mining files, registers and technical indications.

Mining authorities by state

The table brings together only the Bergbehörde and Altbergbau information recorded in the state entries. It does not establish that a particular Flurstück is free of workings. Before buying, ask the competent office using the complete Flurstück designation and intended project. State law and local procedure may determine whether the municipality, a Regierungspräsidium or another specialist office receives the request. Record in writing whether the response is a map search, a formal statement, a hazard assessment or merely a referral. The entries reflect the relevant state information as recorded; changes and case-specific decisions remain possible. Recheck the response if the building area, foundation or use changes.

Put the documents in order before notarisation. A land analysis makes open mining questions visible in the purchase process.

Sources and editorial status for Altbergbau

The framework includes the Bundesberggesetz, especially §§ 69, 114 to 120 and 125, the Einwirkungsbereichs-Bergverordnung, §§ 873 and 1018 BGB, § 19 GBO and § 311b BGB. The Bundesanstalt für Geowissenschaften und Rohstoffe and the specialist offices linked in the state table provide additional context. Status: 7 August 2026. Check the linked federal provisions and state authority information against current versions before use. The sources show the legal framework and competence, not that a property is free of voids. Document the Flurstück, investigation scope and contractual consequences separately. Map versions, authority structures and technical methods may change; an old response should be checked again before construction. A summary does not replace review of the original file by the appointed experts and of the complete draft contract. General information, not legal advice.

Two neighbouring checks belong in the same purchase file: the ordnance check before a purchase, buying at a forced auction.