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)
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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