Hi always_learning
Major and Minor Domestic Building Contracts are available for purchase at hardware outlets such as Bunnings for about $40.
These Contract pro-formas include space for the builder to disclose the operating margin to the customer.
10% is very low. After all, for a job this size he stands to earn only about $1000, less GST, $900. At a professional rate of $50 per hour that's 18 hours.
The Contracts make provision for the builder to tell you 'that's how much the materials cost' and that's how much they cost. If you withdraw materials from the quote and substitute them with other materials, eg withdraw galvanised guttering and replace with Colorbond or viceversa, the builder is entitles to make whatever adjustments they see fit, including retaining their margin if, for example, you wanted a tool cupboard then decided not to have it after all.
The builder has had to measure and quote for the tool cupboard or contact a cabinet maker for a quote, and just because the customer decides they can live without it the builder is still entitled to claim their on-costs regardless.
If, on the other hand, you have organised to have the builder do his own work and supervise the work of others eg the plumber or drainer, and you have negotiated an hourly rate, then the builder is entitled to charge a supervision fee for when he is on site overseeing other contractors.
It would be no surprise if the hours applied to the job exceeded 18 hours and the labour charge to the customer was significantly higher than the $1,000 margin as quoted.
At under $12,000, keep in mind that the job is also likely costed to be under the $12,000 Builder's Warranty threshold. It's amazing how many jobs get costed to $11,995. Which means no insurance and no warranty. However, if you decided that you wanted a nice cupola on the roof to finish the job off, and that would push the quote to $12,050, don't be surprised if you are told 'Listen, mate, I'd have to charge you $395 to go to Bunnings to get the cupola and fit it, they're only $123.50 off the shelf, why don't I leave you a bit of flashing and a few nails and you can do it yourself? Save yourself $395 and you can do it yourself in an afternoon!'
Please don't think me cynical - some of my best friends are builders - but it is very common for builders to 'helpfully' suggest that the customer 'deal direct' with the tiler or the painter or whatever, so that the builder does not have to quote for that part of the job and the 'cost' stays under $12,000.
But it's a tough game, the building game, and if your builder can do the job you ask for at the price you're happy with, then good luck to him if he can get the bricks laid in 13 hours not 15, or he can source guttering cheaper than he thought he could. Provided that you get what you specify eg 'two coats of Dulux paint' and not get fobbed off with 'buy one, get one free' no-name paint which peels off like sunburn, everybody's happy.
Cheers
Kristine