Before you can mount the generator on the roof there are few thing you will need to check it out with the building engineer to make sure they can support the weight of generator unit and other requirement needs.
and get a rough idea how big the generator size wise you want and let us know or concat the generator manufacter they will give you a listing of weights of the units and footprint size as well so you will know much weight it will sit on the roof.
I am not too suprised there are some case you may have to add addtional support braces or beams to handle addtional loads.
And mount them with viberation isolators to keep the noise down.
If this is Natural Gaz it is not too bad but with Diesel fuel you may have to find a way to bring up fuel to the unit so that is the other item you may have to look at it.
I have installed couple units on the roof and I will say run by the buiding engineer first to make sure they can support as I mention earlier.
Merci.
Marc
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)
| 
