Skylight Installation Costs

Real cost ranges by service, and the factors that change them.

Most of the price of a lantern sits below the glass: the upstand, the trimming and the weathering that keeps it dry.

Nobody can price a rooflight honestly over the phone, because the unit is rarely the expensive part. What sets the number is the hole: what has to be cut, how the materials get up there, what the roof build-up is already doing, and how much plastering and decorating follows once the glass is in. The figures on this page are the general shape of the UK market for this kind of work. They are guidance to read someone else’s quote against, not a price list, and the only number that means anything for your roof comes after somebody has stood on it.

Where the money in a rooflight job actually goes

Split any installed price into six parts and the arguments about cost start to make sense.

The sealed unit and frame. On a straightforward roof window swap this is often the largest single line. On flat-roof and lantern work, where a kerb has to be built and an opening formed, it usually is not.
Forming and trimming the opening. Cutting the roof, transferring the load off whatever has been removed, and building the timber the unit will sit on.
Weathering. Flashing kits on a pitched roof, membrane dressing and upstand detailing on a flat roof. This is the part that decides whether the installation is still dry in ten years.
Access. Scaffolding, tower hire, and on larger glass, a lift or a crane. Purely a function of where the roof is and what is underneath it.
Making good inside. Insulating and boarding the reveal, plastering it, and decorating. A separate trade visit, and a real cost.
Paperwork. Building Control notification, and a structural engineer’s calculations where the opening needs them.

Two quotes for the same house usually differ on the last three, not the first. That is worth knowing before you conclude that one installer is expensive. A price that only covers the glass, the hole and a bit of flashing will always look better on paper than one that carries scaffolding, a plastered reveal and the notification, and you will pay the difference later either way.

Typical installed price ranges by service type

These are industry-typical ranges for supplied and installed work on a domestic property in the south east, per unit, including labour and standard weathering. They exclude VAT treatment questions, scaffolding and internal decoration unless stated, because those vary too widely to bury inside a single figure.

Type of work	Typical installed range	What the bottom of the range assumes
Direct swap of an existing pitched roof window, standard size	£700 to £1,300	Sound existing opening, ladder or tower access, matching flashing kit, no internal work
New roof window into a pitched roof, between existing rafters	£1,400 to £2,400	Traditional cut roof, no rafter altered, single splayed reveal
Roof window where a rafter or truss member has to be trimmed	£2,200 to £3,500	Engineer’s design already in hand, straightforward loft access
Conservation-detail roof window in a conservation area or Article 4 zone	£1,600 to £2,800	Flush-fitting unit with a central glazing bar, planning consent already granted
Replacement unit onto a sound existing flat-roof kerb	£900 to £1,800	Kerb square, dry and correctly sized; membrane in good order
Fixed flat-roof rooflight around 1.0 by 1.0 metres, new insulated kerb	£1,200 to £2,200	Joists run the helpful way, one joist trimmed at most, felt or single-ply covering
Opening flat-roof rooflight around 1.0 by 1.5 metres	£2,000 to £3,600	Manual operation rather than electric, no separate structural design
Roof lantern around 1.5 by 2.5 metres on a new upstand	£3,000 to £6,500	Powder-coated aluminium in a standard colour, hand-lifted in sections, level access to the rear
Large lantern or a run of linked units over a full-width extension	£6,500 to £12,000	Repeated standard sizes rather than bespoke, one visit, one access arrangement
Walk-on or structural glazing	£4,000 upwards	Engineered build-up specified by the supplier, craneage priced separately

The top of each range is not padding. It is what the same job costs when the access is awkward, the structure has to change, the glass is specified properly for a south-facing plane, and the reveal is plastered and painted rather than left as bare board.

The factors that move the number

If you want to predict roughly where in a range your own job lands, read down this table and count how many rows apply to you.

Factor	Typical effect	Why it moves the price
Access and scaffolding	£600 to £1,200 for a rear elevation, more with a pavement licence or stepped ground	Two-storey rears, tight side returns and terraced streets with no rear gate all force a scaffold where a tower would otherwise do
Structural work	£300 to £600 for calculations, plus the steel or timber and the labour	A trussed roof cannot have members cut without a design. A cut roof can often be trimmed in timber on site
Roof type and covering	10 to 25 per cent on the installation labour	Plain clay tiles, slate and pantiles each need a different flashing approach. A warm-deck flat roof needs the insulation carried up the kerb
Unit size	Not linear; price steps up at each structural threshold	Anything past roughly 1.2 metres across the joist or rafter direction leaves standard trimming behind and becomes a designed opening
Glass specification	10 to 20 per cent on the unit for solar control; more again for triple	Coatings, argon fill, laminated inner panes and warm-edge spacers all sit in the unit price rather than the labour
Operation	£400 to £900 over a fixed unit	Manual poles are cheap. Electric openers, rain sensors and wall controls add hardware and an electrical connection
Internal finish	£250 to £450 per reveal	Splayed reveals throw more light and take longer to board and plaster than square ones. Decoration is usually separate again
Planning constraint	Application fee plus drawings, and often a costlier unit	Conservation areas and Article 4 Directions can require a flush conservation-pattern rooflight rather than the standard product
Lifting method	From nothing to four figures	Double glazing runs roughly 25 to 30kg per square metre and triple around 40kg. Past a certain pane size it stops being a two-person carry
Number of units on one visit	Reduces the price per unit	Access, mobilisation and Building Control are shared across the job rather than repeated

The lines that quietly get left off cheaper quotes

Comparing two prices only works if both cover the same scope. These are the items most often missing from the cheaper one.

Scaffolding. Sometimes quoted as a provisional sum, sometimes left for you to arrange, occasionally not mentioned at all.
Plastering and decoration. A reveal boarded and taped is not a finished reveal. Ask whether skimming and painting are in or out.
Insulation at the reveal. On a pitched roof, the perimeter of a new opening is exactly where cold bridging and pattern staining start if the insulation is not carried through properly.
Electrical supply for a powered unit, a rain sensor or an integrated blind. Typically £150 to £350 depending on the cable run and whether a spur already exists nearby.
Blinds. Factory-fitted pleated or blackout blinds usually run £150 to £400 per unit and cost far less to fit at the same time than to retrofit afterwards.
Waste and roof reinstatement. Tiles get broken. Someone has to source matching replacements on an older roof, and on a 1930s roof they are not always still made.
Building Control notification. New and enlarged rooflights are notifiable. We make that notification to Southend-on-Sea City Council, or to whichever authority covers your address, as part of the job.

Why a fixed price needs a survey

There are five things nobody can establish without looking, and every one of them can shift a price by four figures.

What the roof is actually made of. A traditional cut roof and a trussed roof look identical from the street and behave completely differently once you want an opening in them. Trussed roofs are engineered assemblies and cutting a member requires a design, which is why a 1970s or 1980s house can cost more to glaze than a 1930s one of the same size.

Which way the joists or rafters run. A kerb set with its long axis parallel to the joists may need one trimmed. Turn the same kerb ninety degrees and it can need three. Rotating a rooflight on a drawing is free; discovering the problem on site is not.

What is under the covering. Deck condition, existing insulation, previous alterations by others, and whether a flat roof is a warm deck or a cold one. This governs how the upstand is detailed and whether the roof around it needs work before anything is fitted.

How the glass gets there. A large pane that cannot go through the house has to come over the roof or up the scaffold, and that decision belongs at survey stage rather than on the morning of the installation.

Which way the roof plane faces. Orientation decides the glass, and the glass is a real line in the price. A north-facing plane wants clear glazing and all the light it can get. A south-facing plane over a flat-roof extension in this city wants solar-control glazing, because Southend faces south across the estuary with an open horizon and very little shading it. Quoting one specification across a whole roof means nobody looked at the compass.

An installer measuring between rafters in a loft with a tape and torch, insulation pulled back at the opening position — The survey is where a range becomes a price. Rafter spacing, roof type and joist direction all change the number.

Reading a quote so two numbers mean the same thing

A quote that says “2 x rooflights, supplied and fitted, £4,200” tells you nothing you can compare. A quote worth holding up against another one names the sizes, the operation, the glass and the scope.

Sizes in millimetres, and how many. Structural opening or unit size, and which of the two is being quoted.
Whole-unit U-value and G-value. Centre-pane figures always look better and are not the comparison Building Control works to. Ask for both numbers on the glass data sheet.
Fixed, manual or electric, and whether the electrical connection is included.
Kerb or trimming detail, including whether insulation is carried up the upstand.
Access arrangement, named and priced rather than assumed.
Internal scope, stated as far as the finish you actually want.
Who notifies Building Control, and whether the certificate comes to you at the end.
The guarantee, separated into the manufacturer’s product warranty and the installer’s workmanship guarantee. Ours is ten years on the workmanship of every installation.

Where spending more pays back, and where it does not

Money spent on the glass is the best value in the whole job. Upgrading a sealed unit to solar control is a modest uplift on one line, and it is the difference between a room you use in July and one you close the door on. The cost of the opening is already sunk by then, and you only get one chance to choose the pane.

Money spent on the reveal detail also pays. A splayed reveal throws noticeably more daylight into the room than a square one for a small amount of extra plastering, and insulation carried properly around the perimeter is what stops a dark damp line appearing at the edge of the plaster two winters later.

Money spent on scale rarely pays in the way people expect. One long slot of glass is not automatically better than three smaller units spread across a roof, and it is considerably more expensive because of the structure, the weight and the lifting. Three well-placed roof windows usually light a room more evenly than one large one and cost less to install.

And money spent on a bespoke shape is the easiest way to double a figure without changing what the room feels like. Standard sizes carry standard flashing kits, standard blinds and a shorter lead time. Bespoke is right when the roof genuinely demands it, and expensive when it does not, which is a conversation worth having at design stage rather than after the order.

We have been installing skylights and rooflights across south Essex for over fifteen years, to current Building Regulations including Part L and Part K, with the Building Control notification made on your behalf. If you want a real number rather than a range, book a survey and you will get a written specification with the sizes, the glass values and the full scope on it.

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