Now I've pretty much seen everything. Typically here in BC we see a vapour barrier on the inside wall of the house against the garage. Sometimes I've seen a vapour barrier on the outside walls of the garage and ceiling too. If there's a bonus room on top of the garage, does the vapour go on the underside of the ceiling? That kind of puts the barrier on the other side of the wall as far as the heated bonus room is concerned.

The other day I saw the sparkies had put vapour boxes on BOTH sides of the garage wall against the house. That I assume is a mistake.

So we take the garage to be a semi-heated area? I don't know if it's code but nearly all the garages in new construction here tend to have baseboard heaters as an anti-freeze measure - presumably people keep the temp in there just above freezing to protect stored paint etc.

What is the correct rule? I can't see the logic in a vapour barrier both sides of a wall, that would seem to be an open invitation to mould.