The loft floor is 8'1" by 8'4" so I didn't have anywhere big enough to build it. This was my solution and it worked like a charm.
The loft floor in place. I nailed it to the walls once I had it square. In hind sight I should have waited until the walls where squared and plumb.
The tarps sag down more then the roof will but it gives a rough idea of the space and the view out the window.
The messy view from the loft over the living room.
The seams in the subfloor are still wet after last weeks leaky tarp so I knew there was some water sitting underneath. I pulled up the one piece of subfloor that didn't have a wall sitting on it and this is what I found. I wedged the neighboring pieces up, vacuumed up all the water I could get at and left them to dry up.