Misted Roof Lantern Glass Replacement

If a roof lantern pane looks cloudy or wet between the two layers of glass, the sealed unit has failed and moisture has got inside. It can't be wiped away, but the unit can be replaced on its own — the rest of the lantern stays.

Roof lantern seen from inside with one misted double glazed pane between clear panes

What are the signs you need misted glass unit replacement?

Fog, droplets or white bloom between the panes
One pane looks hazier than the others
Misting that comes and goes with the weather
Water marks or tide lines inside the unit

What usually causes it?

Edge seal failure

Every sealed unit has an edge seal and desiccant. Once the seal fails, humid air gets in and the desiccant saturates.

Water sitting on the edge

If the unit's edge sits in water because the eaves don't drain, the seal fails sooner.

Movement and age

Thermal movement and age wear the seal; units at the bottom of the lantern often go first.

How do we fix it?

Measure and specifyWe measure the unit and confirm glass spec, thickness and coatings, including a laminated inner pane where needed.
Order the unitThe replacement unit is made to size.
Swap and sealCappings come off, the old unit comes out, the new one goes in on correct setting blocks and the bar is resealed.

Can misted lantern glass be repaired without replacing it?

Not reliably. Drilling and drying services exist for vertical windows, but for overhead roof lantern glass we replace the unit, because the seal that has failed is the thing keeping moisture out. A new unit also lets you upgrade to solar control or self-cleaning glass.

What glass should go back in?

We match the existing units as closely as possible for appearance, and recommend a laminated inner pane for overhead glazing in line with Rooflight Association guidance. Our guide on laminated vs toughened glass explains why.

What should you expect to pay for misted glass unit replacement?

Guide price, per glass unit£245–£595 ex VAT£294–£714 inc VAT · depends on size, glass spec and access

Guide prices assume a standard lantern on a single-storey roof with safe ladder access. Where a tower or scaffold is needed we add it to the quote (typically £245–£895 ex VAT). Diagnostic visits start from £145 ex VAT. Your fixed price is confirmed in writing before any work starts. See all guide prices.

Where is this on the lantern?

Highlighted in amber: sealed glass units.

Do you need permission for this work?

Straightforward repairs don't normally need building regulations approval or planning permission. Replacing a whole lantern, changing its size or working on a listed building is different, and the rules vary by nation:

England

In England, replacing a roof lantern or rooflight is generally treated like replacing a window: the work must meet the Building Regulations (energy efficiency under Approved Document L, and safety glazing), and it's either done by an installer registered with a competent person scheme or notified to building control with an application. Enlarging the opening always needs a building regulations application. Replacing only the sealed glass units in an existing frame is usually treated as a repair rather than notifiable work, but the new glass should be no worse than before — if you're unsure, check with building control. We confirm in writing which route applies before any replacement.

Listed buildings need listed building consent from the local council for alterations, and conservation areas can have extra controls; like-for-like repairs are treated differently from changes, so check with the council's conservation officer first.

Wales

In Wales, building regulations are devolved and the Welsh Government publishes its own Approved Documents. Installing a new rooflight generally needs approval; for a replacement, the Welsh Government suggests using an installer registered with the relevant competent person scheme, or otherwise involving building control, and the new lantern must meet the Welsh energy-efficiency requirements. We confirm in writing which route applies before any replacement.

Listed buildings in Wales need listed building consent from the local planning authority for alterations, with Cadw guidance on historic buildings; check with the council before changing a lantern on a listed property.

Scotland

In Scotland, the Building (Scotland) Regulations 2004 and the Technical Handbooks apply. Under schedule 3, replacing a rooflight including its frame doesn't need a building warrant but must meet the building standards in full; other work to a rooflight, including reglazing, must leave it no worse than before. New or enlarged openings are different and normally need a warrant. We confirm in writing which applies before any replacement.

Listed buildings in Scotland need listed building consent from the planning authority for alterations, with Historic Environment Scotland guidance; check before changing a lantern on a listed property.

Northern Ireland

In Northern Ireland, the Building Regulations (Northern Ireland) 2012 and the Technical Booklets apply, administered by your council's Building Control service. Replacement glazing, including rooflights, must meet the energy-efficiency requirements, and an application may be needed depending on the work. We check with Building Control and confirm in writing which route applies before any replacement.

Listed buildings in Northern Ireland need listed building consent from the council for alterations; check with the council's planning service before changing a lantern on a listed property.

Questions about misted glass unit replacement

How much does a misted lantern unit cost to replace?

Usually £245–£595 ex VAT per unit depending on size, glass spec and access, confirmed in writing before work starts.

How long does a replacement unit take?

Units are made to measure, so there's a lead time between measuring and fitting. Fitting itself is usually a short visit.

Will the new pane match the others?

We match tint and coatings as closely as possible; a new unit can look very slightly clearer than older neighbours.

Where do we carry out misted glass unit replacement?

We cover the whole of the UK. Choose your area for local details and towns we cover.

Misted roof lantern glass replacement