Hi my question has 2 parts about piles and creating a subfloor.
I want to install a 4.8x4.8m (~16'x16') summerhouse; its existing floor is 24mm (~1") floor boards on 75x50mm (~"2x3") floor posts.
I don’t want a concrete base so I thought I could create my own piles using 110mm (~4.5") pipe (filled with postcrete and topped with damp-proof membrane) for the sub floor to rest on.
Is 110mm (~4.5") good enough or should I get 150mm (~6")? How deep should I go with the piles and at what spacing.
I then want to create a base frame for the summerhouse to go on and was thinking that as it already comes with a 75x50mm (~"2x3") floor I could create another one (joist running the opposite way) with 75x50mm (~"2x3") timbers.
Are these good enough timbers for the sub floor as I don’t want to go too high either? what spacing should I have between them?