I hate to bring this thread up again, but I learned quite a few new things on my last safety at heights course.
Over here, if you work at any further in the air than 3 metres (9')you are required to have some sort of a fall-arrest system at the very least.
It is very simple and cost-effective to install a temporary system to cover this sort of thing.
Think of the cost of rehabilitating a guy back to a certain standard of health and mobility, after falling from an elevated position.
WorksafeNZ, says doing nothing, is not an option.
If you are working up in a roof void as the OP was, it would be very simple to install a temporary safety and rescue line tied off to say a couple of vertical beams and then everyone uses them to attach their harness via say a shock-absorber that will only allow you to fall 600mm (2') at the most and you can move anywhere along them lines.
The rescue line attaches to the back of your harness and it uses a rope slip method to bring someone down to floor level in a controlled fashion when a fall does occur.
