Installing free standing oven with stainless steel splash back. Guide states that the wall behind must be "fire resistant". Is there an AS on that? If so where can I source materials? Or, is the current Masonite wall with the stainless steel splash back enough?
The relevant Australian Standard is AS 5601: 2013, which states that 0.4mm stainless steel splashbacks can be installed directly over 12mm fibre cement board, or 6mm fibre cement board over 10mm gypsum board.
You should talk to a licensed gasfitter or electrician about whether or not your splashback is appropriate - one or the other will need to sign off on the installation of the oven anyway. Likewise, if you need more specific information about approved products, you should have a chat with your state building authority (e.g. the Queensland Building and Construction Commission if you're in Queensland).
You haven't mentioned whether or not it's a gas or an electric oven, but we ran your question past Gary Busbridge (Standardisation Manager and Clipsal) and he's suggested that he'd treat electrical and gas ovens similarly with respect to the splashback. He's also suggested you check the manufacturer's installation requirements for any specific details.
Hope this helps,
The BUILD team.