The short answer
On large old roofs the weak points are rarely the covering itself. Valley gutters, parapet gutters, outlets, lead flashings and rooflight surrounds funnel water to a handful of small places, and when one fails the water arrives fast. We start there and work outwards.
Thrupp's mills grew up beside the river, the canal and the road, and their roofs show it. They were built to cover wide floors, so a roof is often a pair of long slopes meeting in a valley, or a run of identical pitches side by side. Each junction where two slopes meet is a gutter in waiting, and a gutter is only as good as its outlet.
Q1.1Why do valley gutters fail first?
A valley is a channel lined with lead or another metal, and it carries rain from two slopes at once. Leaves, moss and silt settle in it, and the lining beneath is seldom seen by anyone. Lead that has stretched and shrunk through many winters can split along its folds, and a patch over a split is only as good as the metal under it. Where the lining is sound we clear it and dress it back into shape, then check the laps and the clips that hold it. Where it has gone, a newly lined valley is the lasting answer.
Q1.2What about parapet gutters and flashings?
A parapet gutter runs tucked behind a short wall along the eave, and its outlet may be no wider than a drainpipe. When that outlet clogs, the gutter fills until water finds the weakest joint. We check that the outlet runs clear, that the gutter has a proper fall, and that the flashing is tucked into a cut in the wall rather than smeared over the surface with sealant. Our commercial roofing page explains how larger buildings are surveyed and quoted.
Q1.3Do old rooflights need replacing too?
Many mill roofs carry rooflights in tired frames. Where the glass is sound and the trouble is at the kerb, the repair belongs at the kerb, not in new glazing. Where a rooflight is being replaced, the new unit has to meet current thermal limits, and our written price says so plainly. Photographs of each valley, outlet and flashing come with it, and the defect is laid out on screen or paper well before you choose a course of action.