Rooflights and skylights in Godalming

Godalming is a market town and civil parish in the Borough of Waverley, Surrey. Waverley Borough Council is based in the town itself, so the planning authority that reads your drawings sits a short walk from many of the roofs in question.

The town lies at the confluence of the Rivers Wey and Ock. The Surrey Hills National Landscape runs to the north and west. The 2011 census recorded 21,804 people in the civil parish and 22,689 in the built-up area, which tells you this is a compact town rather than a scatter of villages, with streets close enough that a roof is often seen from a neighbour's window.

Surrey County Council sits above the borough and gives heritage advice on conservation areas. For a household the practical point is simple: the borough council decides the application, and the county's heritage advice informs it where an old building is involved.

The town centre appraisal counts 125 statutory listed buildings inside the Town Centre Conservation Area. Of those, 122 are Grade II, three are Grade II* and one is Grade I: the Church of St Peter and St Paul.

That is a high density of protected buildings, and it changes how a roof opening is approached. A listed building needs listed building consent for works that affect its character, which is a separate process from ordinary planning, and a rooflight in an old roof can count. Nobody should cut into a listed roof on the strength of a web page, including this one.

For buildings like these the usual starting point is a slim, flush-fitting unit on a slope that is not seen from the street, in a proportion that sits between rafters rather than cutting them. Our page on conservation rooflight installation sets out the product and the detailing. Where the roof is protected, the quiet question is still real. A flush conservation rooflight can be built with a laminated inner pane and proper seals, and the written spec records the choice.

The railway through to Portsmouth opened in January 1859, and the current station dates from that year. The Guildford and Godalming bypass, now the A3, opened in July 1934. Those two dates give Godalming two steady sources of background sound that we can write into a specification.

Neither is aircraft. The research for this town does not source aircraft noise, so the noise angle here is road and rail, plus rain on glass, and nothing else.

Road and rail sound is a low, continuous band rather than a single event. It reaches the room through the thinnest part of the house, which is the roof, and a loft bedroom is the room most exposed to it. A thin double-glazed unit with tired seals lets a lot of that band through. The answer lies in the build of the unit, not in making it bigger:

• a laminated acoustic inner pane, with the outer pane at a different thickness, so the two panes do not ring at the same pitch;
• a cavity chosen for the noise as well as for heat;
• compressed seals all round the sash and the frame;
• on a flat roof, an upstand built up tall enough to be finished properly.

Different Godalming roofs suit different products. The table is a starting point for the survey, not a substitute for it.

These questions come from the town's own setting: the conservation areas, the listed buildings, the railway and the bypass.