Moderators: Random Orbital Bob, nev, Charley, CHJ, Noel

By Tony K
I'm building a raised timber pond for the garden and would appreciate some advice on the load bearing capability of the timber structure. The pond is 1.8m x 1.2m and 1.1m high, using 32mm thick, 140mm wide T&G timber and a PVC liner. The corners are notched and very tight with solid interlocking joints. It will hold 1650 litres of water.

I'm trying to work out the pressure on the structure walls and the load bearing capacity of the wood, and prove that the current design is up to it. Also, I wouldn't mind scaling up the design and would like to know how big I can go.

I've made a few calculations and have a good idea of the force on the walls due to hydrostatic pressure, I reckon it is 10.7 N/mm² (1.5psi). I can't figure out how to calculate the bending capability of the timber, it is C16 Grade T&G, 140mm wide. There seem to be plenty of span tables available but they're more concerned with loadbearing joists taking the weight along the grain.

Cheers in advance.