Roof lantern installation in Birmingham

A roof lantern sits on a raised kerb above the flat roof, which keeps the glass clear of standing water and gives the roof covering something to turn up against.

At the survey we check the roof deck, its finish and its fall before we suggest a kerb height. A deck that is sound and dry can usually take a new opening. If the deck has gone soft, or the covering on it is well past its best, the plan for the lantern changes.

Whenever the lantern job is notifiable, the notice to Building Control comes from us.

What the kerb does

The kerb lifts the lantern frame above the roof surface, carries its weight down into the joists and gives the roof covering a clean upstand to seal against.

Its height inside also matters. A taller kerb gives a deeper plastered box between the ceiling and the glass, which changes how the light spreads into the room. We show you the kerb detail on the quote so the finish inside is not a surprise.

How we decide which shapes to quote

We start from the room. A long kitchen and dining room under a rectangular opening suits a hipped lantern, traditional or slimline. A square garden room or the middle of a square extension suits a pyramid. Where the opening could go either way, both go on the quote.

Then we look at the house. A traditional lantern with deeper bars sits comfortably on a Victorian or Edwardian terrace in Moseley or Kings Heath. A slimline frame often looks better on a newer, plainer extension. These are starting points rather than rules, and your own preference counts as much as the house.

Aluminium is strong enough to carry wide glass panels on slim bars, which is why it is the usual frame for a larger lantern. It is powder coated, often in grey or black, and can be ordered in other colours to match your windows and doors.

A uPVC lantern, usually with an aluminium core, costs less. The bars are wider, so you see more frame and a little less glass. On a smaller lantern over a utility room or a modest kitchen the difference is easy to live with, and the saving can be put towards the glass.

Where both frames suit the opening, both appear on the quote. Our guide to aluminium and uPVC roof lanterns lays the two out on sightlines, strength, U-value, colour, lead time and price.

Self-cleaning and safety glass

The outer pane can carry a self-cleaning coating that breaks down dirt in daylight and lets rain wash it away. It helps on a lantern you cannot easily reach, though it still needs an occasional rinse.

The inner pane of a lantern is usually safety glass, and where it is laminated, a broken pane stays in place rather than falling into the room. The quote states which safety glass the maker uses for each unit.

Glass decides most of what a lantern feels like to sit under. A double glazed unit with a warm-edge spacer and argon gas can meet the Part L limit, and the maker states the figure for each lantern. Triple glazing keeps more heat in on a winter evening but adds weight, so the frame and the kerb have to be specified for it.

Glass also decides summer comfort. A large lantern over a south-facing kitchen in Hall Green or Solihull can make the room hot on a bright afternoon. A solar control coating reflects much of that heat while letting daylight through. Our page on energy efficient rooflights explains the coatings and the figures that makers publish for them.

On a north-facing roof, or under trees, the balance shifts. Summer heat matters less there, and some people would rather have the clearest glass and the best winter figure. That is why the glass is chosen for each roof, and why the same lantern can appear twice on a quote with two different glass specifications.

We size a lantern for the room you sit in, then check the roof can take it.

Planning permission

Permitted development can cover a roof lantern, and the conditions it has to meet are laid out in our rooflight planning guide. A lantern stands well above its roof, so it is the product most likely to fall outside those conditions and need an application, and our answer on whether a roof lantern needs planning permission applies them to lanterns.

Listed building consent is required for any new rooflight on a listed building, no matter what permitted development says elsewhere. The right can also go if an earlier planning permission carried a condition against it, or if an Article 4 direction applies, so at the survey we look into what governs your address and report back to you. The council makes the decision.

Across Birmingham, some streets in Moseley, Edgbaston and Harborne sit inside conservation areas. A lantern on a rear extension frequently cannot be seen from the street, yet the rules for your address still have to be checked. Should an application be required, we can provide the lantern drawings and product details for it.

What goes into the price

A lantern price is built from the lantern itself, its glass, the kerb, the roof covering around it, any trimming of the joists and the plaster finish inside. The quote itemises every one of those lines under each option, which lets you follow the money from line to line.

Our answer on how much a roof lantern costs to fit explains each part. Torn between a lantern and a flatter unit? Our answer on a roof lantern or a flat rooflight sets the two against each other.

A typical fitting starts by making the opening safe and weathertight, which keeps the room below protected if the weather turns. The lantern frame is fixed to the kerb, the glass goes in, and the roof covering is dressed up the kerb and sealed.

Indoors, the kerb gets a lining and a plaster skim, which makes the light box read as a natural part of the ceiling. Some people add a light strip or spotlights in the kerb. If you want those, tell us at the survey so the cable goes in before the plaster.

After it is fitted

When the visit ends we tidy the site, demonstrate any vent or blind, and pass you the maker's paperwork and, where the work was notifiable, the Building Control certificate.

A 10-year workmanship guarantee stands behind the fitting, while the maker's own warranty continues to cover the lantern and its glass. Details of the cover are on our guarantee page.

Looking after a lantern is simple: rinse the glass now and then, clear leaves from the roof around the kerb, and check the roof covering when you check the rest of the roof.