The answer
Conservation rooflight cost moves with the size of the unit, a steel or aluminium frame, the centre glazing bar, whether it opens, and the work the roof needs: slate or stone, trimming and flashing. We price it after a free survey, and the quote is fixed in writing and names what is being fitted and where.
Size, frame and bar: what you pay for in the unit
The unit itself is where the first price differences arise. A conservation rooflight in slate is made to a slim, flush pattern, and each choice within that pattern adds or removes cost.
- Size. A larger frame uses more metal and thicker or heavier glass, and it needs a bigger opening in the roof. Two small units over a landing are priced differently from one large one.
- Frame material. Aluminium is slim, strong and light, and it is finished in black or charcoal. Steel-faced frames give the narrowest sight lines and weigh more, and the weight feeds into the roof work as well as the unit.
- The centre bar. A frame made with a central glazing bar is a different product from one with a single pane, and a conservation officer may ask for the bar on a street-facing slope.
Glazing sits on top of those choices. Sealed double glazing is the starting point, with a coating and spacers chosen for heat loss, and the extra glass of a triple-glazed unit or a laminated inner pane moves the price too. Part L sets the energy limit the unit has to meet, which the guide to efficient rooflight glazing breaks down.
Finish is the last unit-side item. The black or charcoal powder coat is usual, and a colour made to order, or a different colour on the inside face, can add to the price where a maker offers it.
A fixed unit or one that opens
A fixed conservation rooflight has no moving parts, so it is the simplest build. An opening unit adds hinges, a handle or a motor, and it adds a sash, which makes the frame deeper than a fixed one. A motorised unit also needs a cable taken to it and a switch or remote, with a rain sensor on some models.
Opening is worth pricing against what the room needs. A landing that already has a window on the floor below may need only daylight, and a fixed unit does that. An attic bedroom that has no other source of air may justify one that opens. Our answer on whether a conservation rooflight can open covers how an opening unit sits in a slate roof.
The roof work around the unit
On a roof of slate or stone slate, the work around the unit often costs as much thought as the unit. A fresh opening alters the roof structure, and any rafter that is cut is trimmed round with new timbers. A replacement of an existing rooflight needs less structural work, and it is notifiable under Part L.
The covering sets its own detail:
- Natural slate takes a flashing dressed close to the slate.
- Stone slate is heavy and laid in diminishing courses, so the opening is set out from the coursing.
- Clay tile takes a flashing formed to the tile profile.
Access adds to the job. A stone terrace with a steep roof and no yard may need scaffolding, and a villa with an easy back lane may not. Inside, the shaft to the ceiling is plastered and decorated as agreed, and the ceiling below can be lath and plaster, boarding or plasterboard, each of which is cut and lined differently.
If the covering is already due for replacement, fitting the rooflight in the same job saves working on the same slope twice.
Swapping an old unit for a new one
When a worn rooflight comes out and a conservation unit goes in, the existing opening may be reused. That saves cutting a new one, but only if the old opening matches the new unit's size and sits between sound rafters. A wider or taller frame means altering the rafters again. We measure the old opening against the maker's drawing before pricing.
Planning and consent work
Where the house is listed or an Article 4 direction applies, the unit needs an application, and the drawings for it take time to prepare. We supply the unit details, and the council's own charges for an application are the council's to set. Which route applies is set out in the conservation areas guide and in the answer on consent for listed homes.
If no application is needed, that part of the cost does not arise. We check the position for your address before any unit is ordered.
How the fixed written quote works
The free survey looks at the room, the roof and the way in. The written quote that follows records which unit goes in, at what size, for a fixed price. We notify Building Control. Two conservation rooflights of one width can differ in price by their frame, their glazing and the roof they go into.
The costs page sets out how every quote is put together. To begin, use the quote form with the address and a photograph of the roof, naming the room that needs the daylight.