Collar beam roofs: structure, costs and limitations
A collar-tie roof is a structure of rafter pairs connected by transverse timber members called collar ties, whose position and connections directly shape how the entire roof truss performs. Before deciding, it is worth establishing whether the design allows the loft to be adapted without removing the collar ties, since this element often limits layout freedom. Check that the collar-tie-to-rafter connections match the solution assumed in the calculations — random screws or extra holes can weaken the timber. The choice of structure is governed by span, loads and how forces are transferred to the walls, not by a sketch alone.
