are outbuildings included in surface area for taxe d'habitation

[tempinfrance]

i have been naughty and posted a similar question on another thread but since realised the question is more simple than i first thought...if anyone knows if outbuildings are included as part of surface area of house i would be grateful. Our (ruined house was about 148 on two floors...its totally not habitable ...not even to enterable!) yet our taxe d'habitation bill is calculated on a surface area on 365m2 ( i called impots and managed to understand that much)j. I'm wondering if outbuildings are included on this bill. The note at the bottom of the bill just says its for one 'maison'. I suppose just because the surface areas are included on the tax habitation bill it doesn't mean they are classed as 'habitable'...or does it! After ages of toing and froing still trying to get to grips with whether i need a permis de construire or not to live in the most habitable of the buildings on my land...which is a barn lived in by previous owner as their house had collapsed! Now i guess it hinges on whether this little barn was included in bill for tax hab'..and if so, whether this means its considered a dwelling.