Help with rigging a walk way to get across an indoor roof please
 

Ok, so this is the situation. We are replacing the insulation and drywall in a commercial garage. There is one section that we have to cross the office roof in order to access it. It is about an 8 foot length, and the roof of the office is would not support the weight of us walking on it. We thought about cutting a hole in the drywall on the other side and putting a ladder there to make a make shift walk way. We are worried that our weight would would cause the ladder to break the dry wall (5/8). So any suggestions for how to rig something to fix this would be greatly appreciated. Thanks in advance.

Why wont the roof support your weight? Has there been problems with structure? Someone had to be on it to roof it, you should be able to walk on it now. What type of roof is it? Post a pic I'd like to see.

What I'm picturing is a large building with an office built inside that does not go all the way up to the roof. Like a building inside a building. If that's right then just use an aluminum walkboard. They make expandable ones that go from 8' to 11". Lowes and HD sell them.
Another way is to use 2, 2 X 4's and a piece of 1/2' plywood. You have the 2X's standing on there sides and just screw the plywood to the 2Xs.

Thats pretty much what it was. The ceiling of the office was just that soft tiling that you see in schools. We ended up just going into the office and taking 2 tiles out and then sticking a ladder up there against the wall above. Took the scizzor lift as far over as we could the set up a plank between there and the ladder. It worked out pretty well actually. I was kinda surprised.