I have never said it did not require Building Control, Approval, merely that the OP is extremity unlikely to face any kind of legal threat if he fails to get Approval.
If it is just to cover what is already there and two large format concrete tiles is the way you are going to roof it then 3"x2" will do for the rafters, I have one of these jobs booked in but I am going to be doing a semi with both people agreeing to get the work done at the same time, the ones I am doing have a steel pole near the doors rather than gallow brackets so it makes things easier in terms of support. If you are going to diy it yourself then its probably best to engineer it to be safe. good luck
Noseall and catlad - Many thanks for your comments - certainly gives me something to think about - the largest gap is 2500mm so may need to look at a bigger beam.
Just out of interest, what sort of price would I be looking at for a job like this?
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