When it comes to doing any sort of renovation, build, or extension, the first thought on everyone’s mind is “What’s it gonna cost?” With the new 70m² granny flat rules being slated for rollout in early 2026, building a granny flat might be quite the viable option, bringing both space and value to your home. Here’s how much you’ll be looking at for a full-sized granny flat. Cost to Build Per square metre, a secondary dwelling typically costs around $3000 to $5000, which means