How much does it cost to replace a rooflight?

A replacement is priced on the unit that goes in, and that need not match the one that comes out. Some owners want the same type again. Others use the swap to move from a fixed unit to one that opens, to upgrade the glazing, or to add a blackout blind for a bedroom under the roof. Each of those choices shifts the figure.

Four things set it:

• Type. A roof window, a flat glass rooflight, a lantern, a walk-on panel and a conservation rooflight are separate products.
• Size. A larger unit costs more, and a unit that differs from the old opening brings building work with it.
• Glazing and finish. Laminated inner panes, easy-clean coatings and the glass specification all vary the unit.
• Operation. A fixed unit is the simplest. Electric and solar opening add parts.

Our guide to what shapes a price in Newport takes the products one at a time.

The smallest swap is a new unit set into an opening that is square, sound and the right size. Whether yours is that opening can only be judged by looking, which is why the survey comes before any figure. Indoors, we look at the lining and the ceiling around the frame. On the roof, we look at the upstand or surround, the timbers that carry it and the way the covering meets the frame.

If the opening is the wrong size for the unit you want, the job has stopped being a plain swap and starts to resemble a new opening. Our answer on the cost of a skylight covers that bigger job. Damp staining, soft timber or a lining that has come away would each add work around the frame, which is why the survey looks for them before any figure is given.

To take an old unit out and set a new one in, the covering beside the opening has to be disturbed. What that covering is, how old it is and how it behaves when worked on all feed into the quote. A sound covering is quick to deal with. A brittle one needs more care and sometimes more material.

The same is true of the roof type. A pitched roof, a flat roof and a roof with a lantern on it are each worked differently, and each is judged on the day we look at it.

Access is the other half. A low single-storey roof can be reached from a ladder and a platform. A high gable, a steep slope above a conservatory, or a terraced house without rear access, can call for scaffolding or other equipment, and a large lantern or walk-on panel also has to be carried to the back of the house, through it or over it. We price what the survey finds, not a standard allowance.

Under the Welsh Building Regulations, swapping a rooflight counts as building work, as roof windows and rooflights are both controlled fittings. Where the work is notifiable, we handle the Building Regulations notification with local authority building control or a registered building control approver.

Approved Document L (Wales) is guidance. It says 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, and a new or replacement rooflight no worse than 2.2 W/m²K. That affects the glazing you choose, and so the price. Our page on replacement rooflights and Part L goes through it, and the Welsh Building Regulations guide covers the rest. On a listed house, listed building consent is needed where the work would affect its character, and the planning guide explains how that is applied for.

The route is short. You book the free survey through the form, we inspect the opening from indoors and from the roof, and the price arrives as a fixed written quote.

Nothing is priced before the visit, and nothing is asked of you for the survey itself. If you would like to start sooner, send photos of the room and the roof to WhatsApp on 07880 284133, or write to info@supremeskylightsnewport.co.uk. The old unit's size code, if it carries one, is worth including. A photograph cannot show the timbers or the covering, so the survey still comes first.