AGW

Hi thanks for replying. 1) I intend to 18mm OSB over the joists and then fit a rubber roof. 2) Yes I plan to use the steel as a lintel.

Hi just looking for a little advice in respect to a Garden Office that I am currently building. The floor span is 4.8m x 4m and the plan is to have a shed partition built into the rear of building which will be 1.8m x 4m and to have the front section house the Garden Office. I two questions I have are as follows; 1) What size of roof joists should I use? I was planning on using 5' x 2' roof joists but a friend had said they may require to be bigger to prevent bowing. Is this the case if there is a supporting stud partition separating the shed section @ 1.8m? 2) Secondly I plan to have 3m bifolds on the front elevation of the building. Given the floor span is only 4m I believe I will need a 160 x 80 x 5.0 rectangular hollow section to support the roof section. Will this be sufficiently strong enough? Any assistance provided will be greatly appreciated.