Rooflights and skylights in Cobham, between the Mole and the A3

Cobham is 28.2 road miles from Crawley, near the far edge of the thirty miles we cover. It is worth the drive, because the village has a clear structure that tells us what to look for before we arrive.

The river runs through the old core. Land rises from about 20 m beside the water to between 60 and 65 m on the watersheds, so a house can stand low by the Mole or well above it, and the wind and the light differ between the two. Cobham is about 17 miles south-west of London, and the pull of the capital is part of why people live here.

The 2011 census counted 9,739 people in Cobham itself and 17,273 in the built-up area that includes Oxshott. That tells us the homes are not confined to one tidy centre. They spread across the old village, the streets that grew once the railway arrived, and the area to the south.

Cobham and Stoke d'Abernon station opened in 1885, and the village expansion quickened once the line was there. A place that grows with a railway collects homes from more than one moment, and the roofs over them were built to more than one idea.

The 1960s brought another change. The High Street was widened, and historic buildings were replaced in the process. Anyone walking it now meets older fabric and newer fabric within a few doors of each other. Downside developed separately, to the south, as its own area with its own character.

The practical lesson is that the roof tells us more than the postcode. In the same village we might meet a loft with old timber that has been altered and strengthened more than once, a flat roof from a later extension, and a newer roof with more modern insulation and felt. We read each from underneath, at the survey, before anything is drawn.

The A3 bounds Cobham to the north and west. M25 Junction 10 is immediately to the south-west. The A307 and A245 give the local connections, and the railway runs through the village. A road corridor is a steady sound more than a sudden one, and it is the kind that thin roof glass passes straight into a room.

We give no decibel figures and claim no number for any house. What we do is listen. A survey in a loft bedroom or a kitchen extension tells us which way the room faces, what we hear and when, and what the roof above us is made of.

Then the glazing is chosen for the answer. A laminated acoustic inner pane, an outer pane of a different thickness and a generous cavity between them will behave differently from a standard double unit. Seals and upstand finish complete the build: an unbroken gasket run, a flashing kit that seats properly, a lined reveal. Our guides on acoustic laminated glass and keeping road and rail noise out through a rooflight set out the reasoning.

Older rooflights go wrong slowly. The unit mists between the panes, the frame dulls, the seal hardens and the room gets colder and louder without anyone noticing the day it changed. When that happens, the answer is to replace the unit, and that is also the moment to improve it.

A like-for-like swap gives you back the light you had. A better unit in the same opening gives you warmer glass, a tighter seal and a quieter room. The guide on replacing an old skylight helps you decide which, and the signs a rooflight has failed lists what to look for. Our page for misted and failed rooflight replacement covers the job itself.

In a conservation area, the replacement is judged against what is there and against the council's appraisal, so the address check comes first again.