How much does commercial rooflight replacement cost?

A commercial rooflight is not priced the way a domestic roof window is. The unit itself is often the smaller part of the bill. The larger part is everything around it: access, safety, keeping the building running while the work goes on, and the state of the roof the old units are sitting in.

The variables that move the number, roughly in order of how much they matter:

• Access. A single-storey warehouse you can reach from a scissor lift is one price. A three-storey roof that needs scaffolding, a mobile tower or a mast climber is another. On tall or awkward buildings the access hire can rival the cost of the glazing.
• Roof type and age. Older industrial roofs are frequently built in cement sheet, and sheets from before the ban may contain asbestos. Anything that disturbs them brings in licensed removal, which is a separate cost and a separate timescale.
• Unit type. A GRP or polycarbonate dome on a builder’s kerb is quick. A continuous barrel vault, a northlight run or a large structural glass panel is slower and needs more careful setting out.
• Quantity. Twenty identical units in a row carry far less cost each than one bespoke opening, because the setting up and the access are shared across the lot.
• Working hours. A live factory, a shop or a school often means evenings, weekends or the summer holidays, and out-of-hours labour is charged accordingly.

Because these stack on top of the glazing, two roofs with the same square metreage of rooflight can come back with quotes that differ by a factor of three. That is normal, and it is why a price per square metre only ever gets you into the right area rather than to a firm number.

The figures below are industry-general ranges for supply and installation on a low to mid-rise roof with reasonable access. They exclude scaffolding, asbestos work and structural alterations, which are covered separately further down.

Across a whole roof, small projects of a handful of domes tend to land in the low thousands once access is added. A full replacement of the rooflight belt on a large warehouse or retail shed runs into the tens of thousands, mostly because of the sheer area of glazing and the scale of the access needed to reach all of it in one visit.

These are the items that catch people out, because they do not appear on a per-unit price list and they are often larger than the units themselves.

• Access equipment. Scaffolding, towers, powered lifts or mast climbers, plus edge protection to work safely at height. On a tall or complex roof this is frequently the single biggest line.
• Asbestos survey and removal. If the existing sheeting predates the ban, a survey is needed before anyone touches it, and licensed removal follows if it is present.
• Structural and weatherproofing work. New kerbs or upstands, flashings and tie-ins to the existing roof covering. Where the old openings are the wrong size for current units, the roof deck is altered to suit.
• Fall protection to the finished roof. Non-fragile rooflights and, where required, guarding or safety netting, which matters for anyone maintaining the roof afterwards.
• Building Control. New or enlarged rooflights are notifiable, with Part L covering thermal performance and Part K covering safety glazing and guarding.
• Downtime. The real cost of closing an aisle, a production line or a floor of a building while the roof is open, which is why phased or out-of-hours working is common.

A sensible quote breaks these out as separate lines rather than folding them into a single rate. If a price looks unusually low against another, it is usually because one of these has been left out, so it is worth checking each is accounted for before comparing two numbers.

Southend-on-Sea faces south across the Thames Estuary, and a great many of its commercial roofs face the same open southern sky with nothing to shade them. That changes what the replacement is worth, not just what it costs. A large area of clear rooflight over a south-facing floor plate is a solar collector, and on a warm day it can push a serious amount of heat into a space that then has to be cooled back down.

Clear double glazing sits at a G-value of around 0.6, meaning about 60 per cent of the sun’s energy comes straight through. Solar-control glazing brings that down to roughly 0.3 for a modest addition to the unit cost. On a shaded north light run that difference buys you little. On a south-facing retail or office roof it can take real load off the cooling system and cut the glare that makes screens and displays hard to read. A replacement is the moment to make that change, because the openings are already there and the only variable left is what goes into them. Our solar-control glazing work is built around exactly that calculation, and it is why we look at orientation before we price the glass.

Start by counting what you have and noting three things for each rooflight: rough size, what it is made from, and how a person would safely reach it. Note which way the roof faces and whether the space below runs hot in summer. Those five facts turn a vague enquiry into something anyone can price properly.

A word on scope: if a single unit has failed and the rest of the roof is sound, swapping that failed unit is a replacement and is our work. If the roof covering itself has come to the end of its life, that is a roofing job and a roofer is the right first call.

For a like-for-like number, look at our skylight installation costs page, then read the detail on our commercial skylight installation hub for how these projects are planned and phased. When you are ready for a figure against your actual roof, ring 01702 898232 or request a quote, and we will price the whole job, access and glazing together, rather than the units on their own.