I need to cast a foundation for a wall, and for the surface levels to be reasonably accurately.
It will be 300mm deep and 600mm wide, with a 68mm step in the top edge so that the rear shuttering only needs to be 232mm tall. The whole foundation will be below ground when completed, so we were looking to back-fill the outsides of the formwork prior to pouring the concrete to help prevent the formwork distorting.
(bad ASCII artwork of design) ||---------|| ||-------|| || || || || || || || ||v^v^v^v^v^v^v^v^v^|| base cast onto excavated surface
Using 18mm OSB as the side shuttering/formwork and 50x50x600mm timber pegs to locate and hold it down, what spacings would you recommend for the bracings? These shutters are a one-off and will be 22m long, so I do not want to make them over strong and waste monies that could be spent elsewhere.
thanks
Tony Strong