Okay, l'll keep this one quick and to the point. This was our first time installing a bath and after sifting through all kinds of advice this is what we did it.
1. We started off by building a timber frame that supports the top lip of the bath all the way around. Because ours is a shower/bath it had to be inset into the wall studs a little to ensure the waterproofed gyprock sits on the inside of the bath lip to prevent leakage.
2. The acrylic bath we were using recommends supporting the base with either timber battens or mortar and we decided to go with mortar.
Tip: Don't use expanding foam - it eventually crumbles, and in many cases is voids the warranty!
The installation instructions call for a minimum of 20mm of 4:1 sand cement mix. We used a basic mortar preparation from Bunnings, mixed it to a damp sand consistency in buckets and made 3 'sand castles' in the middle then squashed them together.
3. We lowered the bath in, squishing it into the mortar, then used a few timber off-cuts to prevent the mortar from spreading too much.
Tip: Don't fill the bath with water unless the instructions call for it - it can cause the base to lift and float above the set mortar once emptied, defeating the purpose.
4. And yes, it's level, phew!
So the bath is in, not the grandest of baths, but still deeper and more comfortable than the one that was there before and it will be perfect for bathing kids. This weekend is quite busy but there should be time to get the electrics attended to, and perhaps pull up some of the slate floor which we've decided to be sensible about and remove. If anyone is after some free slate let me know :)