Rooflight and Skylight Costs in Cambridge

What you are actually paying for

A rooflight cost in Cambridge is the sum of about six decisions: the unit, the glass, how the roof is reached, what the structure needs, how the inside is finished and whether Building Control is involved. The unit is often the smaller share.

Price lists online tend to show the glazing on its own, sometimes with a fitting figure added as if every roof were the same. They are not. A roof window going into the rear slope of a gault brick terrace in Romsey, reached from a flat-roofed back addition, is a different job from the same window going into the front slope of a three-storey Edwardian house in De Freville Avenue, where the scaffold has to stand on the pavement. The window might be identical. The day, the kit and the risk are not.

That is why this page does two things. It gives general UK market ranges, clearly labelled as a guide, so you can tell whether a budget is in the right area. Then it spends most of its length on what moves a rooflight or skylight job up or down within those ranges, so you can read any quote, ours or anyone else's, and see where the money goes.

One thing sits underneath all of it. The cheapest rooflight is the one you only buy once. A unit in the wrong position, or with the wrong glass for its slope, costs you twice: once to fit, and again in blinds, fans or a replacement to deal with heat and glare you did not plan for. The light plan we write with every quote exists partly to stop that second bill.

Typical UK ranges, as a guide

These are broad UK ranges for supply and installation, drawn from the cost guides that UK trade platforms publish from real homeowner quotes, last checked in September 2026. They are a guide to scale, not our price list, and a survey is what turns them into a real figure for your roof.

Treat each row as a spread rather than a target. The low end assumes a straightforward roof, easy access, a standard size and plain glass. The high end assumes some combination of a larger or made-to-measure unit, upgraded glass, structural trimming and full internal finishing. Scaffold is listed separately below because not every job needs it.

The sun tunnel, roof window, flat rooflight and lantern rows follow published installed averages closely. Fewer installed figures are published for conservation and walk-on rooflights, so those two rows combine typical unit prices with a standard fitting cost, and a survey matters most there.

Some items sit on top of those ranges when a job needs them:

Published guides mix figures with and without VAT, so read these as approximate and check whether any quote you receive includes it. None of the figures include planning or listed building consent fees. They also assume the rest of the roof is sound. If a flat roof needs recovering at the same time, or a pitched roof is being retiled, that is roofing work with its own cost, although doing the rooflight in the same programme often saves a second round of access.

The unit: type, size and frame

The unit sets the floor of the price. Type matters first, then size, then whether it is a standard catalogue size or made to measure.

A pitched roof window is the most standardised product in the trade. Manufacturers make a fixed run of sizes to suit common rafter spacings, and flashing kits are made to match them. That standardisation keeps the unit cost down and makes the fitting predictable. A VELUX window swapped like for like into an existing opening is the simplest version of all: the opening is there, the lining is there, and a matching flashing kit goes back in.

Flat roof units are less standard. A flat roof rooflight sits on a kerb or upstand, and the unit can be framed (glass in an aluminium or uPVC frame, with a drainage path) or frameless (glass bonded to the kerb, with a cleaner look from below). Frameless units usually cost more for the same clear opening, and they need a kerb built true, because there is no frame to take up small errors.

A roof lantern is the most variable of all. The price climbs with the footprint, and it climbs faster than area because larger lanterns need heavier ridge and hip sections, more glazing bars and thicker or toughened panes. Aluminium lanterns cost more than uPVC and give slimmer sightlines, which matters when the whole point is to see sky rather than bars.

Size also has a less obvious cost. Once a unit goes beyond what two people can lift safely up a ladder or through a house, it may need a hoist or a crane, and a crane in a narrow Cambridge street can mean a road licence and a booked day.

The glass, and why it is worth spending on

Glass is where a small increase in spend buys the most change in how the room feels. It is also where the light plan earns its place, because the right glass depends on which way the slope faces.

The baseline for a new or replacement rooflight in England is Part L of the Building Regulations. Under the 2021 edition the limiting U-value for rooflights is 2.2 W/m²K, and it is now assessed with the unit lying in the horizontal plane rather than upright, which is a harder test. Any competent unit sold for domestic use meets that figure, so the choices above it are about comfort rather than compliance.

The options that change the price are these:

• Double or triple glazing. Triple costs more and weighs more, which can affect frame and kerb size. It pays back most on a north slope or a large lantern where heat loss in winter is the concern.
• Solar control coatings. These lower the g-value, the share of the sun's energy that passes through. On a south or west slope over a kitchen or loft bedroom, this is often the single most useful upgrade.
• Laminated inner pane. Overhead glazing should hold together if it breaks. A laminated inner pane is the usual answer, and it is expected where people stand or sit beneath the glass.
• Self-cleaning outer coating. Useful on low-pitch glass that rain does not wash well.

Our energy efficient rooflights page goes further into U-values and g-values. For costing, the point is simple: a cheaper pane on the wrong slope is paid for later in blinds and discomfort.

Opening, electric control and blinds

A fixed unit is the cheapest version of any rooflight. Each step towards opening and automation adds hardware, wiring and time.

A manual opening roof window within reach costs little more than a fixed one. Once the window is out of reach, above a stairwell or high in a vaulted ceiling, you are into a winding rod or an electric motor. An electric opening rooflight needs a power supply run to it, which means an electrician, a route for the cable and somewhere to put the switch or receiver. Rain sensors that close the unit when the first drops fall are usually part of the package and are worth having on any unit that opens.

Opening units also have a job beyond fresh air. Warm, damp air collects at ceiling level in kitchens and bathrooms, and an openable rooflight is often the most effective way to let it out. If a rooflight is doing that job, it is worth paying for an opening one rather than adding an extractor later.

Blinds are the item people leave off a budget and then buy anyway. Internal blackout blinds suit bedrooms. External awning blinds stop the sun before it reaches the glass, which makes them far better at keeping a south-facing loft room cool, and they cost more. Fitting blinds at the same time as the window is cheaper than coming back for them, and on an electric unit they can share the same controls.

Access and the roof you have

Access is often the largest variable in a quote after the unit itself. The same skylight can cost noticeably more to fit on one house than on the next.

A single-storey rear extension with a flat roof can usually be worked from ladders and a tower. A roof window on the rear slope of a two-storey terrace may be reachable from the back addition roof. A front-facing window on a three-storey house, or any work above a conservatory or over a neighbour's ground, generally needs scaffold. Scaffold is priced by height, run and duration, and on a street-facing elevation in the city it may need a licence from the highway authority.

The roof covering matters too. Concrete interlocking tiles are quick to cut into and flash. Plain clay tiles and natural slate take longer, need more care to reinstate, and on older houses the battens and felt behind them may need attention once opened. A single-ply or felt flat roof needs a proper detail around a new upstand, and on an older flat roof the question is whether the covering will accept that detail cleanly or should be renewed around the opening.

Houses in villages such as Grantchester, Great Shelford or Histon often have older, softer roofs than the new homes at Eddington or Trumpington Meadows. That is not a problem, but it is time, and time is cost.

Structure: rafters, joists and upstands

Cutting a hole in a roof removes part of what holds it up. How much work it takes to make that good depends on the size of the opening and how the roof is built.

A roof window sized to fit between existing rafters needs little structural work. A wider window, or two side by side, means cutting one or more rafters and trimming the opening with doubled timbers either side and new members above and below. On a modern trussed roof that trimming has to follow the truss manufacturer's or an engineer's detail, because trusses are designed as a system and cannot simply be cut.

On a flat roof, a new rooflight needs a kerb or upstand, typically at least 150mm above the finished roof surface, built on trimmed joists and insulated to current standards. A lantern over a new extension is usually planned into the structure from the start, which keeps the cost down. Adding one to an existing flat roof means opening up and trimming joists that were never designed for it.

Walk-on glass sits at the far end of the scale. A walk-on rooflight has to carry people and furniture, so it needs continuous edge bearing, a level and square opening and, in most cases, an engineer's check. That design work is a real line in the price.

1. Joists, with doubled trimmers either side of the opening to carry the loads of the cut joists around it.
2. Deck (usually 18mm ply or OSB) with a vapour control layer laid on it.
3. Insulation boards above the deck (a warm roof), often tapered to give the roof its falls.
4. Waterproof membrane dressed up the upstand and over its top, so the joint is lapped, not sealed.
5. Upstand, or kerb: insulated timber, finishing at least 150mm above the finished roof surface to keep standing water and splash off the joint.
6. Rooflight unit fixed over the kerb, its frame skirt shedding water outside the membrane turn-up.
7. Plastered reveal lining the opening from the ceiling up to the frame, finished white to bounce the light down.
8. Roof falls to an outlet: designed at about 1:40 so the finished roof never falls less than 1:80.

Inside: lining, plaster and making good

A skylight is not finished when the roof is watertight. The inside of the opening, the part you look at every day, is a separate piece of work, and quotes vary most in how much of it they include.

In a pitched roof the opening needs a lining: insulated reveals, a vapour control layer, plasterboard, plaster and trim. The shape of the lining changes the light. Splaying the bottom reveal so it runs vertically, and the top reveal so it runs horizontally, spreads the light across the room rather than casting a hard edge. That takes more time than a square box lining, and it makes a visible difference.

A flat rooflight or lantern needs its light well lined, plastered and finished to match the ceiling. On a replacement, the old lining may be sound or may have stained or softened around a failed unit. Some quotes stop at the plasterboard and leave plastering and decoration to you. Ours include plastering and making good inside, and the written quote says exactly where the work stops, so there is no gap between what you expect and what is left on the day.

Building Control, planning and conservation areas

Paperwork has a cost, but it is usually modest next to the build. Getting it wrong costs far more.

A new rooflight or roof window in an existing house is generally notifiable under the Building Regulations, because it affects structure, thermal performance and, in some positions, fire safety near a boundary. We handle the Building Control notification where the work is notifiable, and the relevant fee is shown in the quote rather than added afterwards. A like-for-like replacement into an existing opening is treated differently from new work, and the quote will say which applies.

Planning is a separate question. Many rooflights fall within permitted development, provided they do not project more than 150mm from the roof plane and do not rise above the highest part of the roof. That changes on a listed building, which always needs listed building consent, on a flat or maisonette, where permitted development does not apply, and in some of the conservation areas across Cambridge and South Cambridgeshire where an Article 4 direction removes it. Greater Cambridge Shared Planning covers both councils and publishes a constraints check.

Where a conservation area applies, a conservation rooflight with a flush, low profile and slim steel-effect frame is usually the unit that gets approved. It costs more than a standard roof window of the same size, and an application adds time and a fee. Both are better known before you commit than discovered after.

1. Is the roof structure altered? For example rafters or joists cut and trimmed to make a new or bigger opening.
2. Yes: usually a Building Regulations application to Building Control (the council or a registered building control approver) before work starts.
3. No, for example a like-for-like replacement: usually self-certified by an installer in a competent person scheme, or notified to Building Control.
4. Is it a listed building or in a conservation area, or a flat? These can change what is allowed.
5. Yes: check with the council first. Listed building consent or planning permission may be needed.
6. No: rooflights on a house are usually permitted development if they stand no more than 150mm proud of the roof slope, sit no higher than the ridge, and any on a side slope are obscure-glazed and fixed below 1.7m. Lanterns often stand higher, so check.
7. Both answered: the work goes ahead. Keep the certificates, since a buyer’s solicitor will ask for them.

New opening or replacement

Replacing an existing rooflight is usually cheaper than forming a new one, because the opening, the structure and much of the lining are already there. How much cheaper depends on what the old unit leaves behind.

A misted roof window with a failed edge seal can often be swapped for a new unit with a matching flashing kit in a few hours. Older pitched roof windows, made before about 2001, may need a specific replacement flashing to keep the same installation depth without disturbing the lining. A failed flat rooflight on a kerb that is still sound is a straightforward change. One on a kerb that has softened, or one that is the wrong size for any current unit, means rebuilding the upstand first.

Replacement is also the cheapest moment to improve the light. If the old skylight gave a south-facing room too much heat, the new one can carry solar control glass and an external blind for little more than a plain like-for-like swap. Our misted and failed rooflight replacement page covers the options, and a sun tunnel is worth considering where a room needs daylight but a full rooflight would be too much, or cannot be fitted.

Why a survey sets the real price

Every item above is something that can only be confirmed standing in the room and looking at the roof. That is why a firm quote follows a survey rather than a form.

At the survey we check the slope and its orientation, the roof covering and structure, how the roof is reached and where scaffold would stand, where cables would run, and what the room below is used for and when. From that we work out where the light should land and what the unit, glass and shading need to be. How we plan the light sets out that thinking in full.

The written quote that follows lists each part of the job separately: the unit and its size, the glass specification, opening and control, blinds, access, structural work, internal finishing, Building Control and any planning route. Alongside it sits a short light plan that gives the position, size, glass and shading and the reason for each. You can see what you are paying for, and you can see what the room will be like.

Every installation carries our 10-year workmanship guarantee. To arrange a visit, book a light survey or message us on WhatsApp.

Questions people ask about rooflight costs

Is a bigger rooflight always better value?

Not necessarily. The price rises faster than the useful light, and on a south or west slope a larger pane adds more heat and glare than brightness. A smaller unit in the right position, with the right glass, often gives the room more usable daylight for less money.

Why do two quotes for the same skylight differ so much?

Usually because they include different things. One may include scaffold, plastering, Building Control and blinds, and the other may stop at a watertight unit. Compare them line by line against the list in the section above, not on the total.

Does solar control glass cost much more?

It adds to the unit price, but the increase is small beside the cost of the whole job, and on a sunny slope it often avoids buying external blinds or a fan later. On a north slope it is rarely needed.

Can I save by supplying the rooflight myself?

Sometimes, but the risk moves to you. If the unit arrives in the wrong size, with the wrong flashing, or with glass that does not suit the slope, the installation day is lost. Having the installer supply the unit keeps size, flashing and glass under one responsibility, which is also what the workmanship guarantee is built around.