As a ballpark starting figure use around $1800 - 2000 per square metre. This just a ballpark figure to use as as starting point and can easily vary either side. So for $150k for that size dwelling is only around $600 per square metre...... Contact a local designer (the good ones understand budgets and costings) and start from there. Material and product choices will vary the cost to construct greatly so keep that in mind. Building costs are always increasing not going down.

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Just like birth, death and taxes, renovation surprises are guaranteed. I think Micheal Bell's suggestion to add a contingency is a good one. Also finalising your design before looking for your builder will save on mid project variations. For those interested in estimating the cost of their renovation before going too far into their plans, try this renovation and extension cost calculator. Good luck. richard@makeovergroup (Melbourne)

You don’t need a builder to remove a shower. Are the shower/headtaps and tiles staying (hard to get a base out without damaging the tiles)? Who’s responsible for rubbish removal?