Stainless steel sheet work - What thickness + sheet size?

[gaz1]

He did mention he would rather not have any stiffeners underneath. Yes the sides will only 100mm high.
Won't really be seen from above. I don't mind welding it up and cleaning etc. as long as it will look nice, not obvious distortion and the welds don't rust over time.
hmmm.. some thinking to do!

Thanks for your input mate , much appreciated

at 1500 wide between the walls you will need stiffeners if you are in an area with a snow reference sue to the weight of snow

either build them into the wall structure or build onto the steel box even water plasma tables have strengtheners due to weight of 4" water

id advise a water collection area where the pumped water could collect and then flow as a 2 meter length of water flowing down the sheet

a one sided pump will flow just on one side therefore not filling the steel valley unless you use a spreader bar where the volume of water is across the wide sheet