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. We carry out misted glass unit replacement across Gwynedd, with a guide price from your photos and a fixed price in writing before any work starts.

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
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.
Roof lanterns in Gwynedd
Western and upland parts of the UK get more rain and more wind-driven rain than the east, and that's what finds weak cappings and blocked eaves first. Lanterns here benefit from a check of the bars on the most exposed face and a clear eaves channel before winter.
Coastal wind drives rain hard against lanterns, so cappings and ridge seals on the seaward face take the most punishment.
What should you expect to pay for misted glass unit replacement in Gwynedd?
Typical range: £245–£595 ex VAT, which is £294–£714 with VAT, per glass unit. Towers or scaffold, where needed, are priced into the quote. Your fixed price is confirmed in writing before any work starts.
Do you need permission in Wales?
Straightforward repairs — resealing, gaskets, cappings, eaves and like-for-like parts — don't normally need building regulations approval in Wales. Replacing the whole lantern or enlarging the opening is different and falls under the Building Regulations 2010 (as applied in Wales); 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.
How does it work?
- Send photosWhatsApp or upload a few photos and tell us when it leaks.
- Guide priceWe reply with a guide price and whether a visit is needed.
- Fixed price in writingYou approve the price and the date before anything starts.
- Repair and testWe fix what's failed, water-test where it matters, and send photos.
Misted glass unit replacement in Gwynedd: questions
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.
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.
Which towns in Gwynedd do you cover?
All of Gwynedd, including Bangor, Gwynedd, Caernarfon, Dolgellau, Holyhead, Llangefni, Porthmadog. Rural and remote addresses are covered by arrangement.
How do I get a price for misted glass unit replacement in Gwynedd?
Send a few photos of the lantern and the problem with your postcode, by WhatsApp or the form. We reply with a guide price and confirm the fixed price in writing before any work starts.
Other repairs in Gwynedd
- Glazing bar and capping repairs in Gwynedd
- Slipped glass panel repairs in Gwynedd
- Solar control and self-cleaning glass upgrades in Gwynedd
- Timber roof lantern repairs in Gwynedd
- Flat rooflight and skylight repairs in Gwynedd
- Leak investigation and inspection in Gwynedd
Nearby areas
- Misted glass unit replacement in Clwyd
- Misted glass unit replacement in Powys
- Misted glass unit replacement in Dyfed
- Misted glass unit replacement in West Glamorgan
- Misted glass unit replacement in Mid Glamorgan
More about misted glass unit replacement · All roof lantern repairs in Gwynedd