Velux Windows Price: What Affects the Cost

Size is the first factor. A larger unit costs more to buy and usually means a larger opening in the roof. Glazing matters next: standard double glazing, upgraded acoustic or safety glass, and triple glazing all sit at different price points. Top-hung, centre-pivot and conservation-style windows also differ, and so does the choice between manual opening and electric or solar operation.

Blinds are worth deciding on early. Fitting them at the same time as the window is cheaper than retrofitting them later, because the window does not need to be revisited.

A window that fits between existing rafters is the simplest job. If the chosen size is wider than the gap between rafters, a rafter has to be cut and trimmers fitted to carry the load around the opening. That adds timber, labour and time, and it is one of the main reasons two quotes for the same window can look so different.

The roof covering affects the work too. Slate and tile need the correct manufacturer's flashing kit for the profile, and the covering around the window has to be cut and made good neatly. A flat roof lantern is a different job altogether because of the upstand and the deck alteration; our guide gives £1,800 to £4,000 fitted for lanterns depending on size.

Ask whether the internal finish is included. Lining the reveals, plastering and decorating can be part of the price or left to you. In a loft or bedroom with a sloping ceiling, the internal work can take as long as the roof work, so a quote without it is not directly comparable with one that includes it.

Check how the window will be insulated around the frame. A poor seal between window and roof structure is a common source of cold spots and condensation, and getting it right at installation is cheaper than chasing it later.

Replacing an old roof window in the same opening is usually more straightforward than forming a new one, because the structure is already there. The cost then depends on whether a like-for-like size is still available, the condition of the timber and covering around the old frame, and whether the flashing needs renewing. If the existing window leaks, the cause should be found first; a failed seal or flashing can sometimes be repaired without replacing the whole unit, which our Velux window leaking page explains.

Many roof windows are fitted from inside, with only the flashing work done from the roof. Higher or awkward elevations can need scaffolding or other access equipment, and that should appear as its own line on the quote. Ask each roofer what access they plan to use.

For a fair comparison, make sure every quote names the same window size, glazing and operation, states whether trimming is needed, and says whether the internal finish and blinds are included. A short written scope tells you more than the total on its own.