Chapter 1: The roof of our timber-framed Crookham Village cottage sags between the rafters. Is it unsafe?
What we find
A dip in the roof line is common on cottages that have stood for centuries. Timber-framed houses were built from green oak and have settled as it dried and twisted. The roof is carried on rafters that may be hand-cut, unevenly spaced and joined with pegs, and the weight of clay tiles has been pressing down for generations. Often the sag is old, stable and harmless. Sometimes it is not.
What matters is whether it is moving. New cracks in the plaster below, a tile course that has opened up, a rafter that has split, or daylight where a purlin, the horizontal beam carrying the rafters, meets the gable wall are all reasons to look harder. Rot in the wall plate, the timber the rafters rest on, is another cause, especially where a gutter has overflowed for years.
What we fix
We start in the loft, photographing the rafters, purlins and wall plate, and probing timber for soundness. A stable, old sag is left alone. We do not force a historic roof straight just for appearance, because that disturbs tiles and invites leaks. If the timbers are sound but tired, we can add sister rafters, new timbers bolted alongside the old, to share the load.
If timber has rotted, we cut out the bad section and splice in new oak or treated softwood, depending on what the building and its listing allow. Any structural change on a listed cottage needs the conservation officer in the conversation first, and the survey photographs help with that. Where the tiles themselves are in good order, we relay them to the original gauge. Our pitched roofing page covers repair and re-cover.