There was no current test certificate or a design verification for the crane.
There was also no test certificate for the lifting tackle and no working load limit had been established for the lifting equipment, WorkSafe said.
"The crane is an obvious hazard and the steps that could have been taken to keep staff safe were not difficult," said Mr Stewart.
True Green Homes Ltd should have assessed and selected the correct lifting gear and used it correctly, he said, including getting the capacity of the lifting tackle and fixings right.
"These steps are clearly set out in WorkSafe's guidance for load-lifting rigging," he said.