Is anyone able to point me in he right direction? I"m building a summerhouse which will be an irregular Octogon. 2 opposite straight sides are 900mm long, 2 opposite sides are 1350mm and the four corners are 1250mm long. I should be ok to work out the common rafters but what are the formulas to work out the hip rafters, bevels etc..? Whats the formula to work out the length of the ridge beam so that the whole roof has the same pitch? ( is that even possible?? )

brain overload time

Thanks