I've been through this earlier this year. I got in contact with the Council and discussed the issue with someone in the planning department. I was informed that I needed to comply with section 9.3.7 of the Brisbane City Plan 2014 (
http://eplan.brisbane.qld.gov.au/) - I believe it's classed as a Domestic Outbuilding.
According to my notes height was not a problem (see PO2 in Table 9.3.7.3) and I explicitly mentioned it to the planner (since I have the 3.5m dome and it's 3.2m tall). The most concern they had was PO4 and PO5 from that same table - essentially you can't make water run off / flow worse than it currently is now. I was lucky in that putting down my slab would actually improve my water flow across the lot and reduce the impact on my neighbour.
The above was based on my area/zone - you need to consider that when going through the material. And you have to read the other sections in the document to ensure "self-assessable" applies to you.
Really, the best thing to do is phone the Council (there's a number on the site somewhere) and discuss the situation. I was pleasantly surprised at how well that went.
