finyo, also be prepared that the answers from them may be much the same if you received here. If I called a local US homebuilder and asked how much it would cost to build a house, I'm quite sure they wouldn't just throw a number out on the table. I wouldn't expect them to. As many here have said repeatedly, there are a number of variables to be taken into account.

10% is actually the rule of thumb number that I have heard used for years. Of that 10%, about 60% typically goes to construction docs and the other 40 goes to the earlier phases of the job. Pre-design, if any, is often done hourly. None of this is set in stone anywhere and it will vary depending on the designer's experience and overhead, the complexity and size of the job, etc. There is certainly nothing alarming or unreasonable about asking 10%, and in design, as in most things, you generally get what you pay for.

I'm glad you guys are growing.

Debating replacing a 10 degree roof with a 45 degree roof to optomise going off the grid. Building is 9 metres wide [includes 500 eaves] by 12 metres long. We would increase the length to 16 metres to cover an existing deck with ancient corrugated plastic roof. Question is cost. We have the room to build the roof on site and crane into place otherwise make it offsite. We would need to put a couple of windows in length to give character. We would use dark grey ribbed coloursteel ideally and reclad south and west walls with the same material. Does anyone out there have an opinion?