Illustration generated for this guide. It does not represent a property for sale.
Compare the building with the documents
A conservatory, converted garage or subdivided floor can change your plans. Request available plans and information, then identify what matches the visible situation. Note differences without deciding yourself that they are authorised or unlawful. The right first step is to identify precisely what needs explaining.
Describe your plans to the municipality
If you intend to alter the property, explain your plans to the relevant department: intended use, volume, access or number of homes. In Wallonia, many operations and building works require permission. An answer about another building is not permission for yours. Ask which checks and procedures apply to your circumstances.
Prepare your next step: Read a property file with a notebook of questions
Do not pay for unconfirmed potential
A listing may speak of potential. Your budget must distinguish what exists from what you hope to obtain. If the purchase depends on an alteration, have its feasibility examined before committing. Retain replies and ask the notary how to address the matter in the sale documents.
Compare actual use with available records
A fitted-out room, extension or additional dwelling may seem to have always been part of the property. That does not remove the need to check relevant documents. Note differences between received plans and what you viewed, then request an explanation. Do not draw legal conclusions from the building’s appearance or a cadastral entry alone. Put questions to the notary and relevant municipal department, giving the address and a precise description of what you need to understand.
Check your own plans before assigning value to a possibility
A deep garden does not guarantee you can extend the house as you wish. A large room does not guarantee it can be divided into several homes. If your purchase depends on an alteration, have that possibility assessed before including its value in your offer. Ask which procedures would be necessary and what remains uncertain. Carefully distinguish existing documents from imagined plans. An attractive prospect should not appear in your budget as an already acquired right.
Keep official replies in your file
Record the date, contact and documents to which each answer relates. A general telephone explanation can point you in the right direction, but ask how to obtain information specific to the property. If a situation requires clarification, establish possible procedures, costs to investigate and effects on your timetable. Avoid deciding alone that regularisation will be easy. Your decision should reflect available information and unresolved matters, with contractual wording reviewed by the notary when this issue determines the purchase.
Sources and references
ComparImmo editorial team. Sources checked on 27 September 2026. Check the rules for the region and your circumstances before making a commitment.