What Is a Conservation Rooflight?

The difference is mostly proportion. A standard roof window sits in a deep frame with a flashing kit that stands a little above the covering, and the frame is often a pale colour. A conservation rooflight takes the opposite approach. The frame is thin, the glass comes close to its edges and the whole unit lies near the plane of the roof.

Seen from the street, that comes down to a thin dark outline round a pane of sky. On an old roof that reads like a traditional cast-iron skylight, which is the effect it is made to give. The design borrows from those old roof lights, which were set into slate roofs on mills, outbuildings and the rear slopes of terraces.

Many units have a single vertical glazing bar running down the middle of the pane. That bar is not there for strength alone. It breaks the glass into proportions that match the older pattern, and it makes a large pane look lighter. Some designs leave it out for a plain sheet of glass.

The word heritage is often attached to these units, and you will see "heritage skylight" as a trade term. It means the same thing: a rooflight designed to suit an older building.

The frame is usually steel or a steel-look profile, finished in a dark colour. The thin section is possible because the frame is strong for its size. Sealed double glazing fills the frame, so the room below does not pick up the cold from the slope in winter. The unit is fixed to a kerb or set into the structure of the roof, and a flashing joins it to the covering around it.

Some are fixed and do not open. Others open on a pivot or a hinge for ventilation. Whether a unit opens affects its price, its look and how readily it can be put through a planning or consent process, so the survey covers that with you before a choice is made.

The flashing is the part that keeps water out, and on an old roof it matters more than the frame. It is shaped to follow the lap of the slate or tile, and it is fitted by lifting the covering round the opening and relaying it over the flashing. The slates stay where they were, so the roof keeps its age and colour.

The glass has to meet the energy rules. Under Part L the rooflight figure for an existing home is 2.2 W/m²K, while a roof window carries 1.4 W/m²K. Which category a given conservation unit falls into turns on the build of the unit, and the surveyor confirms that before ordering.

Conservation rooflights suit roofs where a conventional unit would look out of place. That includes slate roofs on Victorian and Edwardian terraces, clay-tiled roofs on older cottages, converted barns and mills, and extensions on listed buildings. They can also suit a modern house where the owner prefers a slimmer look.

The usual spots inside are the ones the roof can serve from a rear slope. A stair that turns in the dark, a back bedroom with a sloping ceiling, a desk under the eaves, a bath in the roof. In each case the question is the place where the light should land, and the unit is positioned to put it there.

Where the building is listed, a conservation rooflight still needs listed building consent, and the position and size go to the council with the application. That process is set out in the listed building guide. A house in a conservation area that is not listed may or may not need planning permission, depending on the area, and the planning route is covered in our planning guide.

A conservation rooflight is still a new opening in the roof when it is fitted where there was no window before, and that is building work. Notifiable work goes through Building Control, and the firm makes that notification with the local authority or a registered building control approver, then installs to current Building Regulations.

The process is the one every job follows. A free survey comes first, with every part of the job seen before a price is mentioned. A fixed written quote follows, and nothing in it moves on the day. A 10-year workmanship guarantee is given in writing. A straightforward single rooflight is usually a day or two of work up on the roof.

To talk about a roof, book a free survey. For the range of conservation work we cover, see conservation rooflights. If you are unsure whether a conservation unit or an ordinary roof window is right for your house, read how the two types compare.