A lantern quotation has more parts than a rooflight one. There is the lantern itself, priced by size, glass specification and finish. There is the kerb, which is carpentry and roofing rather than glazing. There is the structural opening in the roof. And there is the lifting and access. Two quotations for the same plan size can differ substantially across those four.
What a rooflight quotation is made of
The general anatomy is on how much does a flat roof rooflight cost.
What follows is only what is particular to a glazed structure standing above a roof.
Why glass area, not plan area
The point most people miss when comparing.
A lantern has sloping faces, so the glazed area is larger than the hole it covers, and a steeper pitch on the same plan means more glass and more frame.
Two lanterns over the same opening can differ by a quarter in material.
The span of the bars
Where the engineering enters the price.
A longer rafter carries more load and deflects further, so above a certain span the sections get deeper, or an intermediate structure is needed, and both cost.
How far it can go is on how big can a roof lantern be.
Slim sightlines
What the premium ranges are actually selling.
A structurally efficient bar that is also visually slim is harder to make, and the difference between a slim system and a chunky one at the same size is visible from inside every day.
It is the item most worth paying for.
Standard sizes against bespoke
A real difference.
Standard sizes are made in volume and are quicker and cheaper. A bespoke lantern made to an opening costs more and is sometimes the only way to get the proportion right.
The glass specification
Not optional on a lantern.
Solar control is normal because a lantern faces several directions at once, and a self cleaning coating is worth having on something nobody will be washing often.
What each does is on what is solar control glass.
Triple glazing
Available and heavier, in both senses.
A triple glazed lantern costs more, weighs more and needs the frame and the kerb to suit, and whether it earns that is a calculation rather than a rule.
The argument is on is triple glazing worth it in a rooflight.
The coating on the frame
Where the coastal position spends money well.
A marine grade coating specification on the aluminium costs a little more at order and is what keeps the finish sound within a few miles of the sea.
It is a specification decision rather than an upgrade to be talked out of.
Colour and dual colour
A modest line, occasionally more.
Standard colours are held. A non standard colour, or a different finish inside and out, is a longer lead time and a step in price.
What suits is on what colour should a roof lantern frame be.
The kerb
A whole trade, and the line most often missing.
Building an insulated upstand, weathering the covering up it and finishing the internal reveal is carpentry, roofing and plastering, and it is not part of the lantern price.
What it involves is on what is a builders kerb.
The structural opening
Where a retro fit differs from a new build.
On a new extension the opening is designed in and costs almost nothing extra. Cutting one into an existing roof means trimming joists and often a designed beam.
Opening panes
A meaningful addition rather than a small one.
An opening face brings an actuator, a control system and usually an electrician, and it changes the frame around that face.
What it adds is on can a roof lantern be opened.
Lifting it into place
The item people never anticipate. Large lanterns and large panes are heavy and awkward, and where they cannot be carried through a house or across a garden, a lift or extra labour is arranged.
Access to the rear of a terrace is the usual difficulty.
Delivery and lead time
Worth knowing for a programme rather than a budget.
A standard size in a standard colour is quick. A bespoke lantern in a special finish with opening panes is a manufacturing lead time, and the roof has to be weathertight in the meantime.
Blinds afterwards
Frequently underestimated. A lantern has several faces, so blinds are a set rather than a single item, and on a large lantern they are a significant separate decision.
The options are on do roof lanterns come with blinds.
Two smaller lanterns instead
Sometimes cheaper and sometimes not.
Two standard sizes can be less than one large bespoke unit, but there are two kerbs, two openings and two sets of trimming to build.
The comparison is on can two lanterns go over one extension.
Why we do not publish a figure
Because the range would be so wide it would mislead.
A standard lantern onto a kerb already built on a new extension, and a bespoke unit craned into a cut opening on an existing roof, are different orders of work.
A survey gives a number that holds.
Where we would spend first
The glass and the kerb. Solar control glass and a properly insulated upstand do more for how the room feels than a step up the frame range does, and both are hard to change later.
How we quote it on a lantern
We quote the lantern, the kerb and the opening as separate lines, because a quotation that shows only a lantern price is not a quotation for the job.
The whole picture is on the roof lantern installation page.
Thinking about this job? We survey across Worthing, West Sussex and the South Downs and give you a fixed price before any work starts, with a 10-year workmanship guarantee.