Renovations inside my unit

Hi, I want to do some very minor renovations to my unit (internally only).  These would include:-

Adding a pair of doors to my internal wall (between my lounge room and dining room) & building a small pantry cupboard in my kitchen? Both of these would be fixing to an internal wall, not an external boundary wall.  

Are internal walls the responsibility of the Lot owner or are they the responsibility of the Common Property?

I am happy to get approval, but I was wondering where the actual divide is?

Thanks

Susanp