There are very few mediaeval BUTT PURLIN ROOFS in Surrey (only five have been recorded by the DBRG). In this type of roof the principal rafters are deeper along their full length, purlins are butted into the principals, and rafters may or may not be butted into the purlins. When recording this type of roof it is important to note whether the purlins are "in line" or "staggered". Post mediaeval roofs generally have staggered butt purlin roofs. Wind braces are uncommon in butt purlin roofs, indeed they are often impossible to fit in butt purlin/butt rafter roofs. The butt purlin roof became more popular as a result of the use of attics for storage, bed chambers, etc. Not only did the roof form leave an uncluttered attic space but it also facilitated the formation of openings for dormer windows which were now necessary. This type of roof is often found in masonry buildings in Surrey.
Joan Harding/Martin Higgins January 1991