dormer loft extension with ensuite

Get a structural Engineer asap to give plans to build to as costs could vary depending on what he/she says. Defo get a professional to undertake the structural work as you would not want to fall through to the bedroom below or staircase come crashing down. Most general builders can give you a blank shell with plumbing and electrics for a reasonable price. Hope this helps.

Most loft conversion specialist would carry out a shell conversion for you. You can then complete the plumbing, electrics, plastering and second fix as and when you can. The loft will be left water tight with windows in place and stairs fitted. You will need structural calculations too but some loft companies may do this themselves. Make sure building control are aware of the job from the beginning.

Well although you can get the shell built there is a lot of connected issues with the build process. As the steels and new floor go down first you may find some back tracking and over sites with things like drainage ( if you are planning an en-suite) and general plumbing which ofcourse may need to run under the new floor. On hand over you may experience a liability of blame should any of it be amiss. The structural builder may have to dry fit drainage prior to floor so this may lead to issues and cost that far exceed any saving. I had a build where plumbing had to run through an I beam to get to an impossible corner and achieve a fall to satisfy regs! This boils down to your experience and monitoring from day one so the hand over ticked all the boxes. Just think it through .... at least with one contractor the liability is clear and undisputed and that one variable may save your bacon on a project that will cost a tonne of cash regardless of the route you take. Good luck with it

I see you have structural plans already, that’s good, and you need to follow those as they conform to building regulations, That is a major expense out of the way. Managing your own project will save you thousands, however make sure your builder is aware of this situation, also make sure you are available during the working day to answer any questions that may arise during the working day, Communication is key, Set out a plan with your builder from the start, Consider all services before walls and floor goes down, Try not to change your mind on design issues half way through, A knowledgeable experienced builder will be happy to guid you, as long as you are happy to pay for his services, Good luck with your build,