Yes, you are supposed to apply to the municipal building authority(often referred to as "bygningsetaten", "teknisk etat" etc). Outside and inside changes must be decleared. As you are in Norway, a variety of fees and taxes can and must be paid. To get reliable answers in this complex jurisdiction you should contact a professional at first. You will need pros in this process whatsoever, so start up with one that can act as "ansvarllig søker"(responsible applicant). Next will be a "forhåndskonferanse" (start-up meeting) at the building authority, or simply a chat with the front desk at the building authority. Larger municipalitites offer english-speaking personnel and/or forms and guides.

This termlist should be helpful: http://www.regjeringen.no/nb/dep/md/tema/planlegging_plan-_og_bygningsloven/ordliste-norsk-engelsk--plan--og-bygning.html?id=462717

Hi Stigf,

Thanks a lot for your answer and your tips. Much appreciated :)
I will of course declare everything and pay fees / taxes if necessary. I want to do this according to the law.

My point is more that I would like to have an idea of the costs / taxes before I go further. That's the reason why I posted here, hoping that someone could give me a rough idea and some rough estimates on my questions:

1 - If I transform my bod into a hybel, it will be seen as an extension of the living space of the house. Is that correct ?
2- more living space = more "fortune" = more taxes. Is that correct in Norway? But who will decide the new value of my "fortune"? And is that something I could guess based on some calculation?
3 - Is there a fee to change the category of a building (from bod to hybel)? If yes, how much can it be?
4 - Is there a fee to change the facade of a building? If yes, how do they calculate this?
5 - Will I have to pay taxes on the rent I get (28%) or can it be considered as the rent of a part of the house / hybel (meaning no taxes)?

I know that this looks like direct questions but the thing is that I would like to understand if this is really a good option for me before I start to pay someone for this.

Any help would be really much appreciated.

Best regards,
Torpen

And thanks a lot for the term list that helps a lot !!!
I have added it to my bookmarks.

1. If the hybel is built without separate kitchen/water closet, it is considered as a part of your main house. If it has kitchen, water closet, living room and is meant for permanent stay, it is independent. If the hybel is in the garage and not a physical part of the main house, it would most likely be considered independent and demand above-mentioned functions. Many municipalites will not consider this as a hybel, as it is not part of your main house. Be aware of variations, as Norwegian municpalities traditionally and legally not is obligated to anyone. At least when it comes to this part of the building act.

2. If it is independent, standard municipal fees for garbage collection, water/sewage might apply. Some municipalites adds property tax as well. "State fiscal unit"(Norway Tax admin, http://www.skatteetaten.no/en/International-pages/) might charge you tax based on the size and age of the dwelling, see http://www.skatteetaten.no/no/Person/Selvangivelse/Bil-og-bolig/Bolig/Likningsverdi/Ny-likningsverdi-pa-boligeiendommer/

3 and 4. Yes. The rates varies between municipalitities. Ask for the front desk at building authority. The pricelist is often referred to as "gebyrregulativ"

5. if the size of the hybel is a small part of the main dwelling, in most situastions the answer is no. If you pay tax, maintenance costs is deductable. http://www.skatteetaten.no/no/Person/Selvangivelse/Bil-og-bolig/Bolig/Utleie/Utleie-av-del-av-bolig/