Hi can someone help,
i am ready to install roof on a simple lean to extension to my kitchen, I have decided to install 2X velox windows and have been advised from Building Control that i need to supply Calculations.
The origonal size of rafters are 6x2 which we have upgraded to 7x2 because the span (3.75)mtr with 400 spacing. we have been advised also to bolt 2 rafters together either side of the velox's for added strength. The Inspector advised us he still needs to see calcs. How do i get calcs without consulting a structural design engineer and paying through the roof?