In Bangor, Gwynedd, as everywhere, 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. Send photos and we'll tell you what we think has failed.

Is it time for misted glass unit replacement?
- Fog, droplets or white bloom between the panes
- One pane looks hazier than the others
- 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.
Movement and age
Thermal movement and age wear the seal; units at the bottom of the lantern often go first.
Covering Bangor, Gwynedd and nearby
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.
Near the coast, salt in the air is hard on aluminium finishes and fixings; washing the frame occasionally and touching in chips keeps corrosion away.
Neighbouring places we cover include Llangefni (8 miles), Caernarfon (8 miles), Llandudno (14 miles).
How much should it cost?
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?
In Wales, like-for-like repairs to a roof lantern don't usually involve building control. A full replacement or a bigger opening is controlled under the Building Regulations 2010 (as applied in Wales), so we set out the route in writing first. 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 Bangor, Gwynedd: questions
How do I get a price for misted glass unit replacement in Bangor, Gwynedd?
Send a few photos of the lantern and the problem, with your Bangor, Gwynedd postcode. We'll reply with a guide price and tell you whether a visit is needed before we can fix the price.
Do you need to visit to price misted glass unit replacement?
Not always. Clear photos are often enough for a guide price. Where the cause isn't obvious, a visit to inspect and water-test is charged from £145 ex VAT, confirmed before we come.
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.
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Misted glass unit replacement near Bangor, Gwynedd
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