roof loading

huangyhg

roof loading
i am in the process of building a garage 9m wide by 6m long.
across the 9m width in the middle is a steel 203mm x 203mm 86kg. timbers 150mm x 50mm x 6m are placed at 90° to the steel, at 600mm c/c. on the outer walls are 100mm x 75mm wall plates. can anyone give me an indication as to the maximum load i can place on this structure. i would like if i can to fit an insulated roofing material. if required i could reduce the 600mm c/c to 400mm c/c. what effect would this have on increased loading.
thanks in advance
        laurie roberts