What a skylight costs in Nottingham, and why we look at the roof first

The product sets the starting point. A roof window for a loft comes in standard sizes made in quantity, so the unit itself is the more predictable part of the job. A flat rooflight may be a standard size or made to order for the opening. A roof lantern is almost always made to measure, with an aluminium frame, several panes of glass and a ridge, so there is more material and more manufacturing in it. Our roof lanterns page explains how they are put together.

Conservation rooflights, with their slim frames and glazing bars, are a specialist product. Walk-on glass is laminated and rated for foot traffic, which makes it heavier and dearer. A sun tunnel is a smaller unit, but the job grows with the length and route of the tube through the loft.

Frame finish plays a part as well. A standard colour is usually simpler than a special colour matched to your windows and doors.

Bigger glass costs more to make, and it is heavier to lift onto a roof. A large lantern or a big single pane of flat glass may need extra hands or lifting gear on the day.

Size also changes the structural work. In a pitched roof, a window that fits between two rafters disturbs very little. A wider one means cutting one or more rafters and framing the opening with doubled timbers, so the roof keeps its strength. On a flat roof the same applies to joists, and an opening that runs across them is more work than one laid along them.

Bigger is not always better for the room, either. We size the opening to the part of the room that needs the light, which often keeps the cost down without losing anything you would notice on a dull afternoon.

This is where two similar-looking jobs part company. Every roof covering is opened and sealed up again in its own way. Concrete tiles, clay tiles and natural slate each take a different flashing. A flat roof might be felt, a single-ply membrane, rubber or GRP, laid as a warm roof with insulation on top of the deck or a cold one with insulation between the joists. An old covering near the end of its life can need more care around a new opening than a sound one.

Access counts as much as the roof itself. A low extension roof you can reach with a ladder from the garden is straightforward. A rear slope three storeys up, a terrace with no side passage, or a roof over a conservatory may need a tower or scaffold, and that is part of the price. Narrow streets where a skip or a scaffold lorry cannot stop easily also make a difference.

None of this shows up in a photo of the room, which is the main reason we look before we price.

Every unit we fit meets the energy limits in Approved Document L for existing homes, so the baseline is already a well-insulated sealed unit. From there, the choices add cost one at a time.

• Triple glazing keeps the inner pane warmer and drier than double, and suits bedrooms and bathrooms, but adds weight and price.
• Solar control coatings cut summer heat through a south-facing roof.
• Self-cleaning outer glass helps on a shallow flat rooflight under trees.
• Laminated inner panes hold together if broken, which matters over a stair or a place where people stand.
• Obscure glass may be required on a side-facing slope, or wanted for privacy in a bathroom.

We will tell you which of these suit your room and which you can leave out. A clear, well-insulated unit is often all a room needs.

A fixed rooflight is the simplest and least costly. It lets in light and nothing else.

An opening one adds hinges, a sash, seals and some means of opening it. On a roof window within reach, that is a handle. Out of reach, it means a pole, or a motor.

Electric operation adds the motor, the controls and a power supply run to the unit. Most electric rooflights can take a rain sensor that shuts them when the first drops land, and some can be linked to a wall switch or a remote. Where a power supply is needed, it is listed on the quote, so it does not turn up later as an extra. Our electric and opening rooflights page covers the options.

If you only want light, a fixed unit is the sensible choice. If the room needs air, a kitchen or a bathroom for example, opening is usually worth paying for.

Replacing an existing rooflight is often less work than starting from scratch, because the hole is already there. If the old kerb is dry, true and high enough to suit a modern unit, the new rooflight can sit on it, and the ceiling inside may barely be touched.

That is not always the case. Older kerbs were often low timber upstands, and after years of wet weather the timber can be soft, or simply too short for current products. Building a new insulated kerb, and weathering it properly into the roof, adds to the job but is the right fix when the old one is the problem. A misted sealed unit is the other common reason to replace; whether that means new glass or a new rooflight is covered on our misted rooflight replacement page.

A new opening, by contrast, always involves structural work, a new kerb or flashing, and finishing inside.

The finish inside is easy to overlook when comparing quotes, and it is where they often differ most.

Once the opening is framed, the shaft between ceiling and glass, known as the reveal, has to be lined, insulated and boarded. The edges are taped and skimmed, and the plaster has to dry before it is painted. Light fittings or smoke alarms in the way may need moving. In a loft, insulation disturbed around the opening has to be put back properly so the room does not lose heat through the gap.

Our quote says how far we take the finish: boarded and skimmed ready for decoration, or painted. It also says how we protect floors and furniture while the ceiling is open, so you know what the room will look like when we leave.

A new rooflight cut into a roof will normally need approval under the Building Regulations, since it changes the structure, the insulation and sometimes the fire safety of the roof. Replacing a rooflight or roof window is controlled work too.

Approval carries a fee from whichever body signs the work off: the council, or a registered building control approver. The fee depends on the body and the job, and it is included in our quote, along with the work of making the notification on your behalf. When the work is signed off, you receive a completion certificate, which is worth keeping for when you sell the house.

Planning permission is a separate matter. Most rooflights on a house fall under permitted development and need no application, though flats and listed buildings are exceptions, as are the few conservation areas with an Article 4 direction. We check which applies before quoting.

After the survey you get a written quote that lists the product and its size, the glazing, how it opens, any structural work, the weathering into the roof, the access equipment, the finish inside, the Building Control side and the disposal of anything removed. The price on it is fixed: what you agree is what you pay when the work is done. To compare two options, a lantern against a flat rooflight for instance, we will price both.

Every installation carries our 10-year workmanship guarantee, in writing. If you are planning around other work in the house, see fitting times for a skylight, which sets out the stages.

To start, send a few photos of the room and, if you can see it safely, the roof, over WhatsApp or through our quote request form. We will book a free survey, look at the roof and the room together, and send the quote after.