Lanterns · rooflights
Roof Lanterns and Flat Rooflights
The least costly time to add or replace a roof lantern or a flat rooflight is when the flat roof is replaced: the membrane is off, the opening can be trimmed, and the new covering is dressed up the kerb in one go.
Lantern or flat rooflight, doing it with a new roof, and what to ask.
Free, no obligation. One local company prices it, not five.
Lantern or flat rooflight?
A roof lantern is a framed glass roof, pitched like a small hipped roof, sitting on a kerb on the flat roof. It brings a lot of light into a kitchen extension.
A flat rooflight is a single sealed glass unit on a kerb, almost flush with the roof. It's lower and neater from upstairs windows.
Both sit on an upstand or kerb, so the glass is above the water on the roof, and both need the membrane sealed to the kerb.
When the roof is replaced
- An existing rooflight stays only if its kerb is sound and tall enough for the new build-up. A warm roof raises the roof level.
- A new opening means cutting and trimming joists. That's a structural change: the roofer should say who designs it.
- Rooflight kerbs and corners are a usual place for leaks: see leaks in heavy rain.
- Order the unit early. Lanterns are often made to size, so the roof may have to be weathered for a while it's made.
What to ask before it's priced
- The make, the size and the glazing of the lantern or rooflight.
- Who forms the opening and the kerb, and who seals it to the membrane.
- Whether the price is the unit only or fitted, and whether VAT is in.
- Whether it opens (for ventilation) or is fixed.
The written price should list the lantern as its own line, apart from the roof.
Flat roof jobs we cover
Flat roof replacementExtensions, garages and dormers. €3,000 to €6,500 on a kitchen extension.More on flat roof replacement →
Flat roof repairLeaks, blisters, split seams, outlets. €250 to €900.More on flat roof repair →
EPDM rubber roofsOne sheet, no flame. €70 to €140 a m² laid.More on epdm rubber roofs →
GRP fibreglass roofsHard and walkable. €75 to €140 a m² laid.More on grp fibreglass roofs →
Torch-on felt roofsThe lowest cost. €55 to €90 a m² laid.More on torch-on felt roofs →
Warm flat roofsInsulation above the deck. €130 to €190 a m².More on warm flat roofs →Flat roofs in every county
- Carlow1.4% flat main roofs
- Cavan0.8% flat main roofs
- Clare1.2% flat main roofs
- Cork2.5% flat main roofs
- Donegal1.0% flat main roofs
- Dublin3.0% flat main roofs
- Galway1.2% flat main roofs
- Kerry1.8% flat main roofs
- Kildare1.0% flat main roofs
- Kilkenny1.4% flat main roofs
- Laois1.2% flat main roofs
- Leitrim1.2% flat main roofs
- Limerick1.6% flat main roofs
- Longford0.9% flat main roofs
- Louth2.3% flat main roofs
- Mayo2.3% flat main roofs
- Meath1.3% flat main roofs
- Monaghan0.9% flat main roofs
- Offaly1.3% flat main roofs
- Roscommon1.2% flat main roofs
- Sligo1.4% flat main roofs
- Tipperary1.6% flat main roofs
- Waterford2.2% flat main roofs
- Westmeath1.5% flat main roofs
- Wexford2.7% flat main roofs
- Wicklow2.7% flat main roofs
Free quote
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Questions people ask
Can a roof lantern go on an existing flat roof?
Yes, but it means opening the roof and re-sealing the membrane around the kerb. Doing it when the roof is replaced avoids paying for that twice.
Do roof lanterns leak?
The glass rarely does. Leaks are usually at the kerb, where the membrane meets the upstand, or where a low kerb lets ponding water in.
Lantern or flat rooflight?
A lantern gives more light and height; a flat rooflight is lower and neater. On a small roof, a flat rooflight often fits better.
Do I need planning permission for a roof lantern?
Ask the council if the house is a protected structure or the lantern changes how the house looks from the street. On an ordinary rear extension it's usually a building, not a planning, question.
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