I built a detached man cave, took me about 18 months, but I did do it all myself, (will post you a couple of pics later), basically I put 1m concrete into a 2m trench, then thermalite block up to damp course, then 6 course of brick with 2m posts at 1m space let in to the brickwork, same posts used for top horizontals using galvanised 'L' brackets on each upright/horizontal junction, every 3m I put in an angled brace between bottom of one post to top of adjacent post. put in spaces for windows and doors as I went. (made the windows myself, got the doors from local recycle center). then fitted the roof trusses, felted and battened (battens spaced for second hand Norfolk pantiles), I then used same felt on the outside of the wood post uprights bottom 6" I put 'flashband' 3" up the post & 3" over the brick base, then the bottom run of felt overlaps the flashband. then nailed up 7" feather edge board (in black), once outside weatherproof, I fitted celotex board between the uprights (I ordered enough to insulate the ceiling as well), then finished the inside with mdf boarding, and the ceiling with plasterboard. (before the celotex went in, I put in the wiring for lights / switches / sockets etc)
I used plastic fascia and soffit in black, (not ideal, but maintenance free). got most of my new stuff from Jewsons (mates son is manager, so managed to get 'mates rates') trusses made locally , and plastic stuff I got via the internet., oh, the floor... .thought long and hard about that.... concrete too expensive, suspended wooden floor too posh and too expensive.... opted to level off soil inside, then got a thumper to compact it, then laid an inch of soft sand, then put in 2 layers of plastic dpc, then laid 30 top quality second hand pallets (must all be the same size), then put in a double layer of stirling board.... been in 6 months now, got 4 bikes at one end , 2 heavy work benches and lathe at the other, and all seems good and stable, floor creaks nicely .... good luck with your project...
