Hi Calandria
Your contract should have clauses that talk about Variations and how they’re properly made; although typically, they involve an agreement between…

Do you have any idea what the cost per m2 is on average?
It'd be whatever your house costs divided by the floor area. Either a base price before extra inclusions,…

Unless you're happy to accept price reduction based on cost per m2, and your builder agrees to that, you need to engage a construction lawyer for proper legal advice.