If you're going to lay boards and / or chipboard, could you make a simple suspended floor (i.e. lay some really basic joists and noggins) underneath that could correct for the slope? You'd correct just by raising one side of the structure with footers screwed into the joists and then supporting it at suitable places.
It's obviously more work, but not that hard I don't reckon. If you were going to lay the floorboards yourself I imagine you'd be able to pull it off.
Might even be able to squeeze some polystyrene insulation material in between the joists where there's space to help a bit with the insulation.
If you're going to lay boards and / or chipboard, could you make a simple suspended floor (i.e. lay some really basic joists and noggins) underneath that could correct for the slope? You'd correct just by raising one side of the structure with footers screwed into the joists and then supporting it at suitable places.
It's obviously more work, but not that hard I don't reckon. If you were going to lay the floorboards yourself I imagine you'd be able to pull it off.
Might even be able to squeeze some polystyrene insulation material in between the joists where there's space to help a bit with the insulation.