rendering inside unit

You are basically correct, in that only the external walls and their rendering are part of common property.  Walls which are only internal are part of the lot, and hence up to the lot owner to maintain.  

However the Owners Corporation could be involved in the event that your building is fairly new and still under warranty, in which case a claim could be made against the builders’ insurer.

Millie – nothing that you’ve said about the responsibility for re-rendering (see post #1) is inconsistent with what DaveB advised in post #2- i.e. the walls that separate units are considered external (or perimeter) walls and are common property.

I recall your earlier posts about your proposed renovations, and whilst your Executive Committee (E/C) and/or Owners Corporation (O/C) is relying upon the model by-law 5 which states amongst other things……

1) An owner or occupier of a lot must not mark, paint, drive nails or screws or the like into, or otherwise damage or deface, any structure that forms part of the common property without the approval in writing of the owners corporation.

…… as you may remember, your E/C and/or O/C has only 2 months to respond to your application to renovate your kitchen, and after the expiry of that time you would be able to seek Orders to settle the issue.

Personally were I in your situation, even though it sounds like your O/C has had past problems with renovations involving its Common Property (hence the proposed Special By-Law), provided your new kitchen is in the same position at the original, if I’d signed a contract with someone to undertake the new installation then I’d simply coordinate the timing of those works with the neighbours on the other side of the common wall, and then tell my contractor to go ahead with caution – particularly as your matter has been dragging-on forever and you, not your O/C, would still be responsible for any future repairs to whatever your contractor screws or nails to the common wall.