Yes, it depends upon your local code. Are you really in Belgium?
In Nevada, a free standing greenhouse that is less that 200 sq. ft. (10' x 20') needs no permit. Over that, permits required but not everyone bothers to get them and nobody checks.
If it is attached to a building, even if there is no opening from the building to the greenhouse, it needs a permit. My greenhouse is attached to my house but there are no doors into my house. My permit requirements were that my greenhouse could withstand winds of 100 MPH and 130 MPH ultimate. In some places, there are also snow load requirements.
It all seems silly but, my greenhouse has withstood 90 MPH winds. I have a friend who has built 3 free standing greenhouses without permits and every one of them has blown away.
I had a surprise visit from the city a couple weeks ago. They saw on aireal photos that we had an extra piece on our house. The building permit said it was a greenhouse but they came out and personally inspected to make sure that's what it really was.
Daisy
