Skylights for stone-built villas in Baildon, with rooflights for their stairs and extensions

Asking the council the right question

Give Bradford Council the full address and ask about two things: a conservation area covering the street, and any Article 4 direction that withdraws permitted development there. Ask separately whether the house itself is listed. In a listed house the consent for listed building work comes first: a new rooflight needs it even though permitted development might otherwise apply, so that answer is worth having first.

Why the slope matters

Where a conservation area applies, the council is mainly interested in what can be seen from the public street. A unit on the rear slope, facing the garden, is far less visible than one over the front door. If the room you want to light could take its daylight from either side, the back is the sensible first choice.

If a unit is needed at the front

Sometimes the room sits under the front slope and nothing else will do. A conservation rooflight is made for that case. It has a slim frame, usually black, often with one glazing bar, and it sits low against the slope, so from the street it looks like part of the slate roof.

Work out the position on paper

Before ringing the council it helps to sketch the roof, mark the room you want lit and note which slope it sits under. A simple photograph of the front and back of the house, with the address, lets the planning officer answer in one go. If the answer is that permission is needed, the sketch becomes the start of the application, and the size of the unit is already known.

Flats and divided houses

Where a larger house has been split into flats, the position changes. Permitted development does not reach flats or maisonettes, so a top-floor flat needs an application, and the lease will say who has to agree to work on the roof.

What happens in the roof space

The roof window is set in the slope, and the ceiling over the landing is some way below it. Between the two, a shaft is framed in timber from the underside of the frame to the ceiling opening. We call that the light well. It is insulated, lined and plastered, and the sides are often splayed so that the light spreads out as it drops.

The angle of the well matters. If it runs straight down the glass looks like a hatch; if the bottom is wider than the top, the landing receives a broad wash of daylight and the shaft almost disappears. We work this out on site because the position of the joists limits how far the well can be splayed.

What the roof shape allows

Hipped ends and short slopes over a landing limit the space, since the frame needs clean roof covering around it. On a tight hipped slope the choice may fall to a small roof window or a sun tunnel instead. A sun tunnel is simpler to fit but gives a smaller pool of light, which suits a landing better than a deep stair.

Reaching a high ceiling

A stairwell ceiling can be six metres above the hall floor, which puts the opening out of reach for any ordinary ladder. Inside, we build a stable platform across the flight to work from, and outside, the slope is reached from a scaffold. Old plaster and lath around the opening is cut back carefully, because the ceiling over a stair is often the oldest in the house and is easily cracked.

Keeping the stair usable

The stairs stay in use while we work. Dust sheets cover the treads and the hall below, a working platform is built over the flight so that no ladder stands on the stair itself, then the sheets come up and the floors are cleaned before we leave.

Choosing the opening type

A roof window over a stair can be fixed or opening. An opening unit is useful on a landing that traps warm air, and an electric one is operated from the foot of the stairs by a switch, so nobody has to reach up to a pole at head height.

Settle the size first

The opening and the kerb are built by whoever builds the roof, and they need to be the right size before the roof deck is laid. Makers measure their stated sizes differently, some to the kerb's inner edge and others to its outer edge. The unit and its size are written into our quote, so the builder works to a known measurement and avoids cutting back an upstand that has already been formed.

Planning for a lantern

A lantern normally stands far higher than the 150mm that permitted development allows a house rooflight to project, so the council's consent may be needed unless the extension's own permission covers it. If the extension has its own planning permission, the lantern is usually shown in the drawings and covered by it. If the extension is being built under permitted development, check with Bradford Council whether the lantern is covered before you commit.

Choosing the frame and the glass

Aluminium gives slimmer, stronger frames and suits larger lanterns, while uPVC costs less. The glazing is what controls the temperature: solar-control coatings cut the heat in summer, and warm-edge spacers with a gas fill hold it in during winter. On a south-facing roof the coating is worth having.

Light at the far end

The lantern is normally positioned over the dining end, away from the middle of the room, since the kitchen units at the near end already have a window beside them. A lantern placed over the table also spreads daylight back along the worktops when the door to the garden is closed.

If the extension already exists

If the room is already built with a plain flat roof, an existing flat roof can usually be cut open for a rooflight or a lantern. The covering is lifted, the deck is framed, and a new kerb is built and dressed with the covering so the junction stays watertight. A roof lantern is the larger gesture; a flat rooflight is quieter and lower.