I prefer not to use a square metre, or any other compound, rate as it is a method that sacrifices accuracy for speed of calculation.
If you want a comprehensive feaso you need to think about a building/investment/development and consider all costs. They can include:
- land
- legal fees
- council fees
- taxes
- stamp duty
- bank fees
- holding costs
- interest
- real estate sale/PM costs
- other associated fees
- consulting
- architectural
- drafting
- engineering
- development fees
- certification fees
- Council infrastructure charges
- demolition
- earthworks
- retaining walls
- foundations
- footings
- sub floor
- slab
- frame
- cladding
- electrical
- plumbing
- air conditioning
- data
- fire services
- other services
- walls (frame, block, other)
- internal and external cladding
- insulation
- roof
- solar panels
- skylights
- doors
- fitout
- waterproofing
- floor coverings
- paint
- cabinetry
- vanities
- benchtops
- shower screens
- bathtubs
- wall tiles
- curtains
- external concrete and asphalt
- stairs
- landscaping (turf, plants, gardens, paving)
- fences
- mailboxes
- clotheslines
- sheds
If you receive a quote from a builder you can cross the things off the list that are covered in the quote, or aren't applicable to the development, and get prices for the remaining aspects.
What Shahin may be talking about is how some builder's advertise prices for particular designs on their websites because from the slab up nothing should change. The wind region of the area will affect certain parts of the structure however by the time you find the price you have likely chosen your region or the builder only builds in a limited area.
The main variable with structural is the type of land that is being built on. The foundation and footing requirements for the same design in two different regions could vary immensely and translate to a price difference of tens of thousands of dollars.