How much does it cost to replace a skylight?

What moves it

Whether the opening is reused. A like for like swap into a sound opening is the cheapest job in this trade. Altering the opening is a different order of work.

Access. Frequently the biggest surprise. A single storey rear slope may be reachable from a tower and cost nothing extra. A second storey or a front elevation over a road generally means scaffold, which is a real line rather than a rounding error.

The unit. Stock size, obsolete size, or made to measure, and the glass specification on top.

The covering. Slate and plain tile are straightforward. Profiled tiles need a deep flashing kit. Obsolete or fragile tiles that break when lifted have to be sourced.

What is found. Soft timber around the opening has to be cut out and replaced, and on a unit that has been failing for years it is a real possibility rather than a remote one.

Doing several together

The single best way to reduce the cost per window. Access is a fixed cost shared across every unit done in the same visit, so two done together are meaningfully cheaper than two done a year apart.

If several went in at the same time they will fail at about the same time, which is the practical argument for doing them all.

What you get for free

Twenty five years of glazing improvement. Low emissivity coating, argon fill and a warm edge spacer are standard now and none was standard then. The room will be warmer, cooler in summer and quieter in rain.

An indicative range first, a fixed price after survey

Send a photograph of the data plate on the sash and we will give you a realistic range by email, free and without an appointment. A fixed written itemised price follows a survey and does not move unless the job changes or something we warned you about is found.

The spread on this job is genuinely wide, and five things account for it.

1. Whether the opening is reused

A like for like swap into a sound opening is the cheapest job in this trade. Altering the opening because the old size is obsolete adds work; forming a new one is a different order entirely.

2. Access

Frequently the biggest surprise and nothing to do with the window. Single storey from a tower costs very little. Two storey means scaffold, and where that scaffold stands on a pavement it needs a highway licence with a fee and a wait.

3. The unit

Stock size, obsolete size or made to measure, with the glazing specification on top. Solar control, acoustic laminate and obscure glazing are each a step up. A conservation unit for a listed or Article 4 property is a different product at a different price.

4. The covering

Slate and concrete tile are straightforward. Profiled tiles need a deep flashing kit. Old handmade clay is slow and a proportion breaks, and matching weathered tile takes time.

5. What is found

Decayed timber around the opening has to be cut out and replaced. On a unit that has been failing quietly for years that is a realistic possibility, and an honest quotation names a contingency with an indication of cost.

The reliable way to spend less

Do several at once. Access is a fixed cost shared across everything done in the same visit, so two replaced together cost meaningfully less than two replaced a year apart.

Units fitted at the same time fail at about the same time, so if two of three have misted the third is coming anyway.

What the quotation should itemise

The unit with model, size code and glazing specification; the flashing kit and which profile; the insulation collar; access and any licence; making good and whether decoration is included; disposal; Building Control; and the contingency.

A single number against skylight supplied and fitted is not comparable with anything.

What moves the number most

In rough order of impact.

Access. A window reachable from a ladder over a flat roof is a different job from one on a third floor above a conservatory. Scaffolding, where it is needed, is frequently the largest single line on a small job.

Whether the size is still current. A stock size arrives in days. An obsolete size means either adapting the opening, which adds carpentry and plastering, or a made to measure unit at a premium with a lead time of weeks.

The covering. Slate lifts and relays cleanly. Deep profile clay pantile needs a specific flashing and careful cutting, and hand made tiles need sourcing to match.

Timber condition. The trimmers around a twenty five year old window have been exposed to any slow leak for a long time. On a replacement it is sensible to carry a provisional allowance so that finding soft timber is a variation rather than a stoppage.

What a quotation should separate out

The unit and its specification. The flashing kit and the profile. The insulation collar. Access. Making good internally. Removal and disposal of the old unit and glass. VAT.

A single lump figure with none of that broken out is impossible to compare against another quotation, and it is usually where the omitted collar hides.