I would need to place 45x145 with a span of 3500mm with cc600 on a loft where one will only be able to sleep on a mattress.
Will it work or is the span too large?
Will it work or is the span too large?
I renovated my crawl space measuring 4 by 4 meters. The original floor joists were 150mm high and it wasn't possible to install larger ones. I glued together two 45/145 beams for each joist, with centers 60 cm apart, and added two rows of nogging in between. On top, I laid chipboard flooring which was glued and screwed to the joists. The result was beyond expectations! The floor is solid 
So if you only have 3.5 meters and are only going to place a mattress there, you'll hardly have any issues with 45/145. My entire house has floor joists around 80/150 and most have a span of 4 meters, and that floor has held since 1936, so...
So if you only have 3.5 meters and are only going to place a mattress there, you'll hardly have any issues with 45/145. My entire house has floor joists around 80/150 and most have a span of 4 meters, and that floor has held since 1936, so...