I am doing a single storey rear extention 3m in length and roughly 6m wide (width of house). Its a terraced house. We want the rear wall to be completely knocked down to create an open plan kitchen-diner. I hired an engineer to design to this effect, he calculated that we would require a steel beam across the ceiling and supported by steel columns on each side. I gave these plans to my builder who has then asked for the length of the steel beam and columns. I than asked my engineer to provide that and he said thats up to the builder to provide or the steel company to come and measure.
Im not sure who to believe as neither of them wants to take responsibility for this and in turn the work to my house is being delayed.