What does it cost to replace a misted rooflight?

This is the first thing the survey settles. If the frame is sound and only the sealed unit has clouded, fitting a new pane into the existing frame leaves the opening, its weatherproofing and the lining alone. If the frame, flashing or kerb is tired too, the job grows into a whole-window replacement with roof work around it. How that choice is made is explained in replacing the glass or the window.

Nobody can tell which job you have from a photo of the cloud, so the survey checks the frame and the roof edge before anything is priced.

A larger pane is more glass, more weight and more handling, and a very large or odd-shaped one takes more making. A made to measure unit is built to your frame's dimensions, so there is no off-the-shelf size to fall back on.

The glass specification moves the figure as well. Glass options such as low-e, solar control or laminate, offered by some makers, each change the weight as well as the price. A heavier unit may be too much for an older frame, and that pushes the job towards a new window.

If a maker made the window, as with a VELUX roof window, that maker's range decides which glass units, flashings and blinds exist for it. A current model may have a matching part ready. An older one may mean a unit made to your measurements by a glazing manufacturer, or a whole new window when nothing sensible can be sourced.

Guarantees from makers vary by maker, and the maker prices its own parts, so that part of the figure stays open until we know what the window is.

A roof window on a low pitched roof may be reached by ladder alone. A rooflight on a tall extension, or a lantern over a house with no side access, can need a tower scaffold or other access equipment. Getting a large pane up and the old one down safely takes time, and the survey notes what access the job needs.

If the job is a whole window, there is also the roof opening to deal with. Pitched or flat, new flashing or a fresh kerb joint at the opening comes with a whole new window.

A replacement is the moment to choose how the window works. Choices run from a control rod to a motor to a solar unit, each priced differently, and a motor means a cable run to a switch. Some makers offer a rain sensor on certain models, which closes the window when rain starts. A new blind follows the window's code and make. A blackout blind, a lighter kitchen fabric and a damp-room type each suit a different room.

Settle these before the order goes in, because once the glass is made to order, a change means a fresh order.

Replacing only the glass, or a window in its existing frame, is not providing a controlled fitting, so the energy limits do not apply to that work. So a glass-only job has no energy figure to meet. A whole new window does. In England, a new or replacement roof window in an existing home should have a U-value no worse than 1.4 W/m²K, or a Window Energy Rating of Band B or better. Glass on a kerb, as with a flat rooflight or lantern, answers to 2.2 W/m²K. Where the work is notifiable, we handle the Building Regulations notification with the council's building control team or a registered building control approver.

We survey for nothing and price afterwards, never from pictures. We measure the glass, check the frame and the roof edge, note the maker, and find out how the room gets used. Only then do we give a fixed written quote. For a head start, send photos of the window and the roof edge to WhatsApp 07880 284133 if you can, and our costs page covers the other kinds of rooflight. Once the new glass or window is in, our 10-year workmanship guarantee takes in the fitting.