Skylights & rooflights in Westbury Chalk hill above, railway terraces below

Wiltshire Council handles planning in Westbury. For listed buildings consent is a separate application, and in conservation areas the council can take a view on a slope that faces the street. The planning guide sets out which jobs need consent and what goes in an application. Around the old core, the usual approach is to leave the street-facing slope quiet and place the opening unit on the slope that faces the garden or yard.

A slim frame for the street side

Do not expect the council to say no outright. In a conservation area the usual question is how the frame, the glass and the way the unit sits in the slope will look from the pavement, which is why a flush, slender design is the first thing to price.

When the front roof must carry glass, a conservation rooflight is built for the job. Its metal frame is thin, its glass sits close to the roof surface, and a single bar divides the pane in the manner of the iron rooflights of the nineteenth century. Whether a given model opens depends on the maker; the guide to steel and aluminium conservation rooflights compares the two frames for strength, finish and sightlines.

Westbury also has plain outbuildings that were once part of the cloth trade: long, low ranges behind houses, some now used as workshops, studios or garages. They tend to have simple pitched roofs, thick walls and few windows, so daylight is the first need. Glass in the roof slope lights the whole length of the room, and if the building is one you want to use in summer, a sash that opens lets out the warmth of a day under tiles.

Roofs with a long history behind them

Stone slate and old clay are heavy, uneven and brittle with age. Lifting them around an opening needs patience, and the covering has to be laid back so that water runs off the new junction. We tell you before the visit ends which material your roof uses, what we plan to lift and how the flashing will be arranged. Rafters in a cloth-era building may be thick and widely spaced, so we go up beside the timbers before quoting, and may suggest a single larger window set between two of them rather than two small ones that each need a rafter cut.

Fitting a new rooflight in place of the old, frame and glass together, is notifiable building work; changing just the sealed pane inside a frame that is still good normally is not. The Building Regulations page explains what that means in practice, and we arrange the notification where it applies. A former workshop or outbuilding at the back of a plot is a good candidate for a flat rooflight, because it brings daylight into a dim room and, if it opens, carries off the heat of a studio, kitchen or office.

The streets between the station and the Market Place hold a third type: bigger Victorian and Edwardian villas, some with attics once used by servants. Their roofs are steeper, their ceilings higher, and their rear slopes broad enough for two matching roof windows. Spacing them evenly across the slope, and clear of any chimney, depends on reading the rafters before a single slate is marked. A pair also helps the room: one at each end gives a cross-draught that a single window cannot.

Semis, landings and box rooms

The box room often becomes a study or nursery. Shut off by a door at the top of the stair, it has no through draught, and a nursery in particular needs a gentle supply of night air. That is what a vent bar is for: the sash stays latched while a narrow gap lets air move.

The interwar semi has a regular roof: two equal slopes, evenly spaced rafters, and a loft that is usually clear. It also has a landing and a box room that depend on the roof for any chance of fresh air. On the garden side, a roof window serves a converted loft well, and for a landing under an unused loft, a sun tunnel pipes daylight along a tube to the ceiling below. Where the loft is becoming a bedroom, roof windows for loft conversions shows how the layout works.

Bungalows and chalet bungalows are the exception to the escape rules: a roof window can be the exit from a bedroom under the slope. Size and sill height decide whether a particular window qualifies, and the fire escape page shows the rule. A two-storey semi with a converted loft is different, because it needs a protected stair.

Estates under the hill face wind that comes off the chalk. A sash that closes properly matters there, and so does a latch that holds the sash a little ajar without giving gusts a chance to swing it. We fit units with that in mind and mention it at the survey.

Flat-roofed extensions on the newer roads

Behind plenty of Westbury houses sits a kitchen or dining room under a flat roof. A single fixed rooflight in the middle looks fine in a photograph but turns the room into a greenhouse on a bright day. A flat rooflight with an opening sash, or a second one beside the fixed pane, lets hot air leave through the very top of the room. If the glass is far overhead, an electric opening rooflight avoids the stepladder, and the rain sensor shuts the sash when a shower blows in off the plain.

Our neighbours at Warminster and Trowbridge have pages of their own, and the arrangements there will feel familiar. What changes the price is on the costs page, and the fresh-air rooflights page shows what an open unit does for a room.