Building a free-standing 'second floor'

[22]

I would like to build a raised area for some extra storage into a unit I have. It's basically an old barn, and I need the build to be free-standing - there's nowhere to fix other than the floor (concrete over scalpings).

Raised floor at around 2.4m and approx 28 foot x 15 foot (just to use metres and feet in the same sentence). I need one of the long sides (28 feet) to have as few uprights as possible. The other long side offers potentially somewhere to fix, but I think the floor level would be higher than the wall goes (and also just a single skin separating 2 units).

The whole building has metal roof trusses (made from angle) splitting the building every 14 feet. These don't look very strong over the span and would effectively divide the new storage into 2.

Any suggestions etc very welcome.

[22]

I was thinking much more 'home-made', temporary and also will need to fit around the roof trusses.

[22]

miniman said:

Scaffolding frame and scaffold boards?

Did think about that, but concerned about the number of uprights. On the scaffold theme, I thought about maybe 'supporting' the existing trusses with a few uprights and then find something to span between them. There's a horizontal piece which runs between the eaves but having painted them some years back - didn't seem very strong.