We have a large attic room which follows the original roof line of our 7m wide freestanding workers cottage. It is insulated, lined, painted, carpeted and has skylight window and whirly bird. The space is accessed by a pull down ladder and has served well as storage, playroom and for occasional kids sleepovers. The flooring is "Structafloor" laid over the existing joists which are very thick and strong old hardwood.

Our local council will allow us to do a roof lift at the rear of the cottage up to about 4 metres wide without having to submit a DA. I think it's called complying development.

I would like to claim the space under that ruling (incase they change it!) by having the 4m wide 'pop out' built. I've been told it will be about 90k to turn it into a permanent bedroom with ensuite and staircase and that it will involve ripping up the existing flooring to strengthen joists with metal. I can't afford that much at the moment.

I'm wondering if there's a way to split the job into 2 parts. Get the 4m wide pop out frame/windows etc. built now, continue to use it as we are at present with pull down ladder and deal with the flooring and staircase later.

Is that viable or does it have to all be done at once for structural reasons?
Would I be best to get a structural engineer in for some advice?

Many thanks