What a sun tunnel costs to fit

A sun tunnel kit has three visible parts: the dome on the roof, the tube that carries the light, and the diffuser in the ceiling. Each comes in more than one diameter, and a wider tube delivers more light into a larger room at a higher cost. A landing or cloakroom is happy with a modest diameter. A long hall or a kitchen corner usually wants the larger one, or two modest ones set apart.

The tube itself comes as rigid lengths or as a flexible ribbed sleeve, and the choice affects both the price and the light that arrives. Rigid tube has a smooth mirrored lining and loses little as it carries light down, but it needs straight runs and angled elbows to turn corners. Flexible tube bends freely but its ribs scatter light, so it suits short, awkward routes. Our guide on rigid or flexible sun tunnels goes into the trade-off, and the choice changes the line for the tube on your quote.

Optional extras on the diffuser

Some kits offer a diffuser with a built-in light for use at night, a vent kit for a damp room, or a smaller dome with a flat-roof curb. Each is a line item, and each is worth asking about only if it fits the room. A hall that is rarely used after dark does not need a night light. A windowless bathroom might.

The longer the tube, the more material it takes and the more light it gives up on the way down. A landing under a shallow loft is the cheap end of the range. A ground-floor bathroom with a bedroom above it has no clear way to the roof, and one in a bungalow with a deep loft might need a long run. Distance is measured from the roof opening to the ceiling opening, along the real route, which is rarely a straight line.

Every bend adds a fitting and a joint to seal, and every joint costs time to make airtight. A route that has to step round a chimney breast, a water tank or a truss can need two elbows where a straight drop would need none. We trace the route from the loft at the survey with a plumb line and a torch, since a measurement from the floor below tells you little about what sits in the roof space. The length limits are set out in our answer on tube length, which covers the lengths where the light starts to thin.

Where a room is too far from the roof for one tube to be sensible, we suggest a different product, such as a roof window in a nearby slope. The quote then prices the better fit.

Cutting round a dome needs different work in each roof covering. Plain concrete or clay interlocking tiles are lifted and cut or notched around a flashing that fits their profile. Plain clay tiles and slate are smaller and more fragile, so the flashing has to be dressed to suit them and the tiles around the opening are lifted and replaced by hand. A flat roof takes a kerb and a different flashing, and may need a new area of felt or membrane welded around the base.

Roof pitch changes the dome base too. Access matters as well: a bungalow roof is often reachable from a ladder, while a three-storey terrace may need a tower or a scaffold board across the back, and the quote carries a line for it. If scaffolding is needed for other work on the house, sharing it can bring that line down.

Conservation settings add another variable. A house that is listed, or whose permitted development rights have been removed, may need consent before the dome goes in, and that adds time to the job. One Class C condition is that the dome stands no more than 150 mm, frame included, beyond the plane of the original roof slope, and we check the dome against it. Our planning permission guide explains the checks, and we run them at the survey.

Inside, the tube has to pass through whatever sits between the roof and the ceiling. That could be a bare loft void, a loft with a layer of insulation, or a floored attic room with boards and storage. Insulation around the tube stops warm air from the room below condensing on the cold metal, so it appears on the quote as time and material. Boards have to be lifted and relaid in a floored loft, and a stack of boxes has to be moved before anyone can reach the route.

The ceiling opening is cut through plasterboard or lath and plaster, and the choice of ceiling changes the work. Plasterboard is quick to cut and patch. Older lath and plaster dust more and need more care, and an artexed or coved ceiling asks for a neater finish around the diffuser ring.

Bathrooms and damp rooms

A windowless bathroom brings three jobs of its own: an airtight seal at the ceiling, an extractor route that stays separate from the tube, and a diffuser suitable for steam. Those add lines to the quote, and our guide to a sun tunnel in a bathroom explains each of them.

Regulations and fire stopping

A new opening in a roof is building work, and we handle the Building Control notification where the work is notifiable. The notification can carry a fee of its own, and the council or a registered building control approver signs the work off. Where a tube passes through a floor or a fire-resisting ceiling, fire stopping around it is part of the specification.

A sun tunnel quote that reads "supply and fit, one tube" with a single figure hides the choices above. A quote that breaks the job into lines lets you see where the money goes and compare it fairly with another. The items worth finding are the dome and flashing for your roof covering, the tube type and length, the number of elbows, the ceiling work and the diffuser type.

It should also say what happens to the mess. Dust from a plaster ceiling and bits of old felt are real, and the quote should state who clears them. Access equipment, if needed, should be listed, as should the Building Control notification. Our fixed written quote gives you a price that holds for the work it describes, and any change to the work is agreed with you before it is done.

If you are gathering more than one quote, ask each firm for the same lines. Two quotes that look far apart often differ in a single choice, such as a different tube diameter or a flat-roof base that one firm included and the other left out. For a sense of how other roof products are priced, our pages on costs and the roof window cost guide use the same line-by-line approach.

Fitting two tubes in a single visit shares the access, the cleaning up and the Building Control notification, so the second tube often adds less than the first. A long upstairs corridor, a landing and the bathroom beside it make a natural set. Where several rooms in a row are dark, a pair of tubes can handle them without a single roof window.

Some rooms are better with something else, and the quote should reflect that choice. A room under a sloping roof with a clear slope above it may suit a roof window that opens and gives a view. A wide flat-roofed extension that is dark in the middle suits a flat rooflight or lantern, which covers more floor than a round diffuser. Our answer on whether sun tunnels work helps decide, and the survey gives the clear call.

To start, send photographs of the dark room and the loft above it through WhatsApp on 07880 284133 or by email to info@orchardskylightsmaidstone.co.uk. The survey is free.