Heimpel_2009_135 HeimpelW. 2009 135 roof building construction wood text ancient Near East Roofing beams are placed 40cm apart. Given room legnth, divides by 60, assuming a beam width of 20cm. Remove one 'beam' from result as final support is a wall, not another beam. cmRoom legnth var2 * 60 beamNumber of beams needed. (var1 / 60) - 1 BuccellatiF.30.02.2018