Every council has different regulations and conditions you need to comply with. So, it is best you check with your respective council regarding planning, building permit requirements. Generally speaking anything above 10 sqm requires a permit in Victoria. Some of the other states might allow up to 20 sqm before a permit is required. Again, best to check with your council.
We can certainly provide relevant information including specifications to assist in your permit application. We provide technical drawing as part of the process which can be used to gain engineering certificate which is referred by different names in each e.g. Regulation 126 Certificate of Compliance in Victoria, Form 15 Design Certificate in Queensland, Certificate of Design Compliance in NSW). If required we can refer you to engineering firms we collaborate with.