Currently thinking of converting loft space into 2 additional bedrooms and hopefully extra shower room and hoping someone can advise. I am guessing it will be messy and costly but also wondering how long approx it will take.
It's a tedious but worthwhile process. Most of the work is carried out from the outside. The messy stage really starts once the builders make a hole in your ceiling to put the stairs in. Final plastering of the rooms is predictably dusty but you have to go with the flow to keep your sanity. Ours took 11 weeks to complete (as planned) but most conversions are done in less time.
Around 6-12 weeks weather dependant. Mess wasn't too bad, one day of black dust when they broke though the 120 yr old ceiling. Then bit of plaster dust. Choose builder wisely ! Agree everything, even who is painting it, tiling it and get a timescale of when you need to buy things like lights, bathroom fittings etc.