If you want to put in windows put the extra posts in first then the girts to them. You can do the same for the door frame opening.
The simple solution to the floor for the loft is to just place the joists on top of the center tie beam to the top of the end tie beam and then place your decking on top of these joists. No joinery just toe nail the joists to the tie beam and nail the decking to the joists.
Good Luck with your project.
Jim Rogers
PS. There is a list of tools for sale in the tool section of this forum.
