In brief
A roof window quote is built from the window itself, the flashing that weathers it into your roof covering, the carpentry to trim the rafters, the access needed to reach the roof, and the lining inside. Each depends on your house, so the figure is confirmed in writing after a survey and not read off a list. The size and type of window usually move the total the most.
- The window: its size, whether it is top hung or centre pivot, and the glass
- The flashing: a kit matched to your tiles or slate, and the pitch of the roof
- The structure: trimming rafters, or fitting between them where that works
- The access: a tower, scaffold or lifting equipment to reach the roof safely
- The inside: the lining, insulation, plastering and any blind
The window and how it opens
Roof windows come in a range of standard sizes, so a stock window in a common size is usually the simplest to supply. Moving to a larger or less usual size adds to the price of the window and to the work around it. The way the window is hinged also matters: a top-hung window is hinged near the top and swings out at the bottom, a centre-pivot window turns on its middle, and each has its own cost and suits different rooms. The comparison is in top hung against centre pivot windows.
The glass changes the price as well. Standard double glazing sits at the base. Laminated panes for safety, toughened glass, noise reduction and extra thermal performance each add to it. Electric opening and a rain sensor are further options, and they bring cable work with them.
Current Building Regulations set a heat loss limit for roof windows in existing homes, and the unit we price meets it.
Flashing for your roof covering
A roof window is made watertight by a flashing, which is a set of sheets that overlap the tiles or slate around the frame. The kit has to match what your roof is covered with: plain tiles, interlocking tiles, pantiles and slate each need a different profile and depth. A deeper or unusual covering needs a special kit, and the roofer's time varies with how the material has to be cut and laid.
Where several windows sit side by side, they can share a combined flashing, which can be tidier and cheaper than separate ones. The choices are laid out in the guide to flashing kits, and the pitch of your roof can decide which are available. A shallow roof can narrow the options, as described in the answer on low pitch roofs.
The roofer who dresses the flashing also needs the tiles or slate to be sound around the opening. Cracked or slipped pieces are replaced as part of the work, and the quote says so if it applies to your roof.
Trimming the rafters
The work that gets least attention in a brochure is often the biggest part of the labour. To make an opening, the tiles and battens are stripped and the rafters are dealt with. If the window can sit between two rafters, the structure is left alone and the job is quicker. If one or more rafters have to be cut, they are trimmed and new timbers take the weight around the opening before the window goes in.
Roofs built with trusses are more restricted, because a truss is an engineered member and cannot just be cut. The question of what can be done without cutting is answered in fitting between the rafters. We look at the roof structure during the survey and say in the quote which approach applies.
Access and working on the roof
Reaching the roof safely is a cost of its own. A low roof at the rear of a house may need only a tower. A taller house, a terrace with no rear access or a steep slope may need scaffolding. Heavy glass or several windows may call for lifting gear, which is arranged with the delivery.
If scaffolding is already up for other work, such as a loft conversion, the cost is shared, and fitting the windows while it is there saves putting it up twice. The quote states what access we have allowed for.
Lining, insulation and decorating inside
The opening in the ceiling needs lining. Many windows come with a factory lining kit that includes the insulation and a collar, which suits a room that is already finished. In a loft being converted, the reveals may be formed in plasterboard and skimmed. The plasterer works after the window is in, so the reveal sits correctly and is not damaged by the fitting.
Blinds are an extra that depends on the window. Many makers supply blinds that match the frame, and an electric window can be paired with an electric blind. Decorating and any painting of the reveals fall to whoever is working on the room, and we agree that in advance so it is not paid for twice.
- Ask whether the lining is a kit from the maker or built on site.
- Ask who plasters the reveals and when.
- Ask whether a blind is included, and whether it needs a cable.
How the quote comes together
The survey is free. We check the roof covering, the structure, the access and the room, and talk through the window options. The quote that follows covers the window and its glass, the flashing, the access allowed, how long delivery will take and what your builder has to do. Delivery time rests with the maker, and it is checked again when you order, so nothing is left to guess.
If the window is meant to be an escape route from a loft, that affects the choice of window and its position, and the escape window answer explains the rules. For a loft conversion more widely, the loft window guide takes it further. Our rooflight costs page explains how pricing works across every product, and the roof window installation page describes what we fit.
