How much does a VELUX window cost to install?

A VELUX quote is really four numbers stacked together, and it helps to see them apart before you judge whether a figure is fair.

• The window. A standard white-painted centre-pivot unit in a common size sits around £300 to £600. Move to a larger size, a top-hung design, a conservation finish or upgraded glass and you are into £600 to £900 and beyond. The manual opener is the cheapest; add an electric or solar-powered motor and the unit alone can climb several hundred pounds.
• The flashing kit. This is the collar of pressed metal that weathers the window into the surrounding roof covering, and it is priced separately from the window. Slate and plain-tile roofs take one kit, deep interlocking concrete tiles take another, and a flat-roof adaptor is different again. Budget £80 to £200, and never assume it is bundled in.
• Labour. Opening the roof, forming the timber trimming around the new opening, setting the window true and weathering it in is typically a one to two day job for one window. That is the bulk of the cost on most quotes.
• Finishing inside. The plasterboard reveal, the skim, the paint, and making good the ceiling line. Easy to overlook and easy for a cheap quote to leave out.

On top of those, a new or enlarged roof window is notifiable under Building Regulations, chiefly Part L for thermal performance and Part K for the safety glazing. That notification carries a small local-authority fee, and it should already be inside the price you are quoted rather than sprung on you later.

Two houses on the same street can get very different figures for what looks like the same window. The variables that matter most are these:

• Size. The jump from a small 550 by 780 mm window to a 940 by 1600 mm one is not just glass. A bigger opening means cutting more rafters and forming heavier structural trimming, so both the unit and the labour rise together.
• New opening versus replacement. Dropping a new window into a roof that has never had one means working from a blank slope and making good a ceiling that was previously solid. Replacing a tired unit in an opening that is already framed is quicker and cheaper, because the hole, the trimming and often the reveal are already there.
• Roof covering and pitch. Natural slate and heavy concrete interlocking tiles are more work to cut and reinstate than a plain flat tile. A steep pitch needs more access kit. A very shallow pitch may fall below the minimum a standard roof window is rated for, which changes the specification.
• Access. A window on a straightforward two-storey rear slope with room for a scaffold tower is cheaper to reach than one on a tall front elevation over a bay, or a third-storey loft where the scaffold has to go up further.
• Glazing. The glass you choose can add more than any other single upgrade, and on a south-facing roof it is the upgrade that actually earns its keep.
• Quantity. Two or three windows fitted in one visit share the scaffold and the setting-up time, so the per-window cost falls compared with a single unit on its own.

The line on a VELUX quote most worth reading is the glazing, because it changes both the price and how the room feels to sit in. Southend faces south across the Thames Estuary, and a great many rear extensions and loft conversions on the 1930s semis across Westcliff, Thorpe Bay and Leigh have their main roof slope pointing straight at the summer sun.

Standard double glazing has a G-value, its solar factor, of around 0.6, meaning roughly sixty per cent of the sun’s energy lands in the room as heat. Put a couple of those into a south-facing loft and it bakes from mid-morning onwards, and reflected light off the estuary adds glare on top. Solar-control glazing brings the G-value down towards 0.3, roughly halving the heat while keeping the room bright. It adds to the unit price, often in the region of £150 to £300 per window, but on a south slope it is the difference between a room you can use in July and one you cannot. On a north-facing roof it is money wasted, because there is no strong sun to block and the winter warmth is worth having. This orientation-first thinking is the whole basis of our energy-efficient skylight installation work, and it is the single question a good installer should ask before quoting glass.

If one figure comes in well under the others, it is usually because something has been removed rather than because the work is cheaper. The common omissions are the flashing kit, priced as an extra once the job starts; the internal plastering and making good, left for you to arrange; the Building Control notification and its fee; and the scaffold or access platform, quietly assumed to be a ladder job when it is not. Ask for the glazing specification in numbers too, because “solar control” is a phrase that gets printed on glass sitting at a G-value of 0.5, and a description is not a figure. A quote that spells all of this out is not the expensive one, it is the honest one.

Work out three things before you ask anyone for a price: which way the roof slope faces, whether you are cutting a new opening or replacing an existing window, and roughly what size you want. Those three answers move the figure more than anything else, and knowing them lets you compare quotes like for like rather than guessing. Our VELUX window installation service page walks through the specification in full, and the skylight installation costs page sets out the wider ranges for lanterns and flat-roof units alongside roof windows.

If you would rather we did the working, tell us the orientation and the rough opening and we will come back with a glazing specification and a fixed price rather than a band. Ring 01702 898232 or request a quote, and we will look at the whole roof, not just the hole you want in it.