Skylights and rooflights for stone cottages and terraces in Thornton's older streets

Timbers older than the standard sizes

Rafters in a cottage of this age are not the regular timbers of a modern roof. They may be wider apart, hand-hewn, or carried on purlins that run across the slope. We find where they are before settling the size, and the frame is placed where the timbers allow. Where one has to be cut, the load is carried round it by new trimmers; that is structural work, and we notify it.

Where the frame goes on the slope

The rear slope is the natural choice, since the front of a street of cottages is seen from the road. A slim black conservation rooflight sits low and is the unit conservation officers often ask for on a stone or slate roof in a protected area. Bradford Council can say whether your street is inside a conservation area.

If the cottage is listed

Listing changes the order of events. Consent has to be sought from the council before anything is cut, however small the unit, and the application needs the drawings and the unit's size in it. How that works is the subject of consent for a rooflight on a listed building.

An unlisted cottage

A house outside a conservation area and not listed is a simpler case, because a rooflight there normally sits within the permitted development limits for height and projection. The conditions are listed in the planning guide for rooflights and roof windows.

The head of the stairs

The best place for the window is directly above the top of the flight, where it lights the landing and falls down the treads. We check the position against the chimney breast, the thickness of the stack and the line of the ridge, since the frame needs clear slate on every side.

How wide, how long

A cottage stair is narrow, so a long, narrow window usually matches it better than a wide one. The VELUX sizes and codes guide explains how the standard sizes are named, and the written quote gives the one chosen for your stair.

Open or fixed

A fixed unit has no moving parts to look after, and an opening one has a seal that wants checking now and then.

A window that opens lets the warm air out at the top of the house, which a stone cottage with small windows does not otherwise manage. A fixed unit lights the stair but leaves the air where it is. If the stair is out of reach, an electric opening rooflight can be worked from the landing wall.

What the loft holds

Between the roof slope and the landing ceiling there is usually insulation, a water tank, wiring or stored boxes. The shaft has to pass them, and we ask for access to the loft so the route is clear before the day. Old cottage lofts can be low, and a long light well is built in sections to suit.

Roof timbers and the shaft

An older roof may have collar ties and purlins that cross the line of the shaft. Where one of them is in the way, the shaft is shifted sideways or the size of the window is trimmed to suit, since a main timber is not removed lightly.

The finish at the ceiling

Where the shaft meets the landing ceiling, the edge is plastered and left ready for paint, so the opening looks like a part of the stair.

Flashing and laps

On an exposed roof, the flashing must be deep enough to shed rain driven sideways up the slope. The side flashings lap under the slates, and the top edge tucks beneath the course above. We lift more of the covering around the frame instead of squeezing a flashing in under slates that sit too tight to it.

Glazing and heat

Stone holds the cold, and a single pane at roof level is the coldest surface in a room.

An old single-glazed rooflight on a stone roof loses heat through its pane. A new unit has to meet the current figures, and a low-emissivity coating on the glass and a thermally broken frame help it do so. The guide to rooflight U-values and Part L gives the numbers, and the section on energy efficient rooflights compares glazing.

Condensation inside

Cold stone, a small kitchen and a steamy bathroom produce condensation, and a glazed rooflight in the roof can show it first. A warmer frame and glass reduce it, and so does an opening unit. Rooflight condensation is a separate matter from a failed seal, which shows as cloud between the panes.

An old unit that has failed

If the house already has a rooflight and the glass has clouded, the edge seal of the double-glazed unit has failed. The haze sits within the sealed glazing, so the unit is what gets swapped. Fresh glass in the existing frame or an entirely new rooflight puts it right, and Swapping a roof window like for like explains the choice.

The lean-to roof

Where a lean-to has a ceiling of its own, a sun tunnel or a small roof window can serve a pantry or a utility corner as well as the kitchen.

Some of Thornton's stone houses gained a lean-to at the back over the years, and its roof is quite different from the main slope. It is low, it is shallow, and the wall of the house stands above it.

A back kitchen under a lean-to has a shallow pitch against the wall of the house. A roof window there lights the worktop, and the flashing along the wall side is the detail to get right. The same roof can take a flat roof rooflight if the pitch is shallow enough for a kerb.