The local town council is the competent regulatory authority and makes decisions on matters covered by the Building Act and the Building Regulations, for example applications for building permits and applications for exemption from the provisions of the Building Act or the Building Regulations. The local authority also decides in matters regarding interpretation of the provisions of the Building Regulations, for example concerning categorisation in various structural classes and fire classes, and compliance with specific requirements.
As regards reused construction products, the local authority determines what documentation is required for the anticipated use. The local authority can also grant exemptions under the Building Act if the required documentation is not available.
On the website of the Danish Authority of Social Services and Housing you can find the current Building Regulations and associated guidelines, etc. The rules set out in those documents must be applied if you want to construct a building in Denmark.