Roof repairs and new roofs in Reigate

What usually goes wrong here

• Mortar ridges and verges reach the end together

  The ridge is the line of tiles capping the very top of the roof. The verge is the sloping edge at the gable end. On the interwar semis and on the 1950s houses at Woodhatch, both sit in a bed of mortar and nothing else holds them. Mortar shrinks, cracks and washes out, the ridge caps start to rock in the wind and the edge tiles lift. Because those roads went up together, one house rarely gets there on its own. A dry ridge and a dry verge swap the mortar for fixings and caps, so there is nothing left up there to crack or repoint.

• Slates go one at a time, and the valley goes quietly

  A slate is nailed to a batten. The slate can be perfectly sound after a hundred and fifty years while the nail rusts away to nothing, and then one slides off on a windy night. The Victorian roads here also tend to be gabled, and where two slopes meet there is a lead lined valley running down between them. That valley is invisible from the pavement, it collects grit and moss, and the lead in it is usually as old as the house. It is the part that puts water through a bedroom ceiling rather than onto the path.

• Gutters fill, and the wall behind takes it

  Between the woods on the escarpment and the commons in among the streets, Reigate puts a lot into a gutter. A blocked one does not usually drip somewhere obvious. It backs up and comes over at a joint or a bracket, which lands the water straight onto the wall face. On a solid Victorian wall that soaks in rather than running off. The stain turns up inside the house long before anyone thinks to look up at the gutter.

• Tile hung walls drop tiles, and soft stone suffers below

  Tile hanging is plain clay tiles nailed down the face of a wall, a roof turned on its side. The nails rust the same way they do on a roof. One tile drops out and the course above it loses what was holding its bottom edge. The older walls here can be Reigate Stone, which is soft and weathers badly once it stays wet. Either way, the roofline above is what protects the wall. Water off a failed gutter or a lifted verge lands on the same strip of wall every time it rains.

• In a conservation area you cannot just put back what you like

  Reigate and Banstead has a number of conservation areas and several of them cover Reigate roads. In most of them the council has an Article 4 direction, which takes away the permitted development rights a house would normally have, so external changes need planning permission first. Swapping a roof covering for a different material is exactly the sort of change that gets caught. Trees are covered too, and cutting one back off a roof needs six weeks of written notice to the council. Worth checking which side of the boundary a house sits on before the work is planned, not after.