The solution to the conundrum is 4.58m. It appears that all agree with the length of the hip on the plan as being 4.243m.

The reasons for the confusion are as follows:

The 4.90m calculation –those who calculated the hip length as being 4.90m used cos 30° which assumes that the hip pitch is equal to the roof pitch.

Using the basic principles of the triangle this is impossible and therefore 4.90m is not the solution.

The 4.58m calculation – those who have calculated the hip length as being 4.58m firstly calculated the height of the roof (from eaves to ridge) by using tan 30° and then used Pythagoras Theorem to calculate a correct hip length of 4.58m.

Christopher Hubble, KS Associates Bedford

Source

QS News