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Legalization of Unauthorized Constructions under the New Building Act

Simply put, a black building is a building, alteration or landscaping that has been carried out without the relevant permission from the building authority or in breach of the permission granted. This includes structures such as small garages, pergolas or greenhouses which would not normally require planning permission but which, if carried out, would be in contravention of current legislation or, for example, a development plan.

A professional discusses the legalization of "black buildings" under the new building code.

Key takeaways

Unauthorised constructions are not subject to a statute of limitations and may incur substantial fines. The building authority can initiate removal proceedings even after many years and impose a fine of up to CZK 2 million, or even CZK 4 million in protected areas.
You can initiate the legalisation process by applying for a retroactive building permit. If removal proceedings have already been initiated, you must file the application within 30 days of their commencement, which will suspend the proceedings until a decision on the permit is issued.
Legalisation requires compliance with regulations and no need for exemptions. The construction must comply with the zoning plan and legal regulations and must not require any exemptions (e.g., from setback distances or noise limits), which you are required to prove.
Neighbours' consent can help with exemptions, but the fine must be paid. The consent of your neighbours can eliminate the need for certain exemptions (e.g., regarding setback distances), and timely payment of the assessed fine for constructing without a permit is necessary for successful legalisation.
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What are "Illegal Constructions"?

In practice, these are most often houses and cottages built without a building permit, or extensions and reconstructions that exceed the scope of the original permit.

Removal of the Construction

When the Building Authority discovers an illegal construction, it will initiate proceedings for its removal. The existence of illegal constructions is generally not subject to a statute of limitations, so removal proceedings can be initiated many years after their completion. In addition to the risk of having to remove the building, you will also be fined up to CZK 2 million. In protected areas, such as national parks, this amount can climb to as much as CZK 4 million.

How to Legalise an Illegal Construction?

Legalising an illegal construction is a way to avoid having to remove it. For an illegal construction to be legalised, you, as the builder, must apply for a retrospective building permit. This application for a retrospective permit must be submitted on the prescribed form, including all necessary annexes. But be careful - if removal proceedings have already been initiated, you must submit the application for a retrospective permit no later than 30 days from the initiation of the removal proceedings.

A timely application will cause the proceedings for the removal of your construction to be suspended until a decision on the retrospective permit is made. Be aware that if your application for a retrospective permit is rejected, it is not possible to apply for it again, and the Building Authority will order the removal of the construction.

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For a construction to be legalised at all, you must first meet general conditions, such as the construction's compliance with the zoning plan and legal regulations. A retrospective permit for an illegal construction must also not require an exemption under other legal regulations, for example, in relation to the protection of plants and animals, or due to a requirement for a construction exemption, such as setback distances and noise levels.

You must then prove that a decision granting an exemption is not required in your case. However, there is an exception to this requirement, which is the consent of the neighbours. It is important to realise that the consent of neighbours often plays a key role, especially if the construction is located too close to the property line. If you provide the neighbours' consent, you can avoid having to apply for exemptions, which could otherwise make legalisation impossible.

Another condition is the timely payment of the fine imposed for carrying out the construction without a permit.

Conclusion

Compared to the previous legislation, the requirements for a retrospective building permit have thus been tightened, which should lead to greater motivation for builders to carry out their construction projects in accordance with Czech legal regulations. However, it should be noted that compared to the original draft of the new Building Act, its final version saw a significant relaxation of the conditions for a retrospective permit, which would have been almost impossible under the original draft of the new Building Act.

About the author

JUDr. Lukáš Slanina
JUDr. Lukáš Slanina

Associate, partner

Lukáš Slanina as one of the partners and attorney at ARROWS focuses mainly on providing legal support to real estate agencies and their preparation for the new real estate law. He leads a team that deals with contractual documentation for real estate transfers, all contractual matters related to the functioning of real estate agencies and successfully represents real estate agencies in court disputes with dishonest clients. He regularly provides legal training for real estate agents.

Disclaimer:

The information contained in this article is for general informational purposes only and serves as a basic guide to the issue as of 2026. Although we strive for maximum accuracy, laws and their interpretation evolve over time. We are ARROWS Law Firm, a member of the Czech Bar Association (our supervisory authority), and for the maximum security of our clients, we are insured for professional liability with a limit of CZK 350,000,000. To verify the current wording of the regulations and their application to your specific situation, it is necessary to contact ARROWS Law Firm directly (consultation@arws.cz). We are not liable for any damages arising from the independent use of the information in this article without prior individual legal consultation.