The old ways are best

Those who calculated the length of the hip as 4.58m were right and those like me who said 4.90m were wrong (letters, 10 June). The reason? The angle of the hip is less than 30 degrees – it must be because the height of the roof is constant, but the plan length of the hip rafter is 1.24m longer than the jack rafters. However, I've been doing it the 4.90m way for over 30 years and will continue to do so. Why? (a) because it takes into account the intersection of the hip/ridge and hip/wallplat; (b) because I was trained to, if anything, overmeasure (it makes up for the things you miss); and (c) it’s quick and easy to do (scale the length of the hip and divide by the cosine of the angle of pitch).

Graham Stow, DRA Bristol