A barrel vault rooflight is budgeted per linear metre of run, typically £600 to £1,400 per linear metre supplied and fitted for a standard-width multiwall polycarbonate vault on a new insulated kerb, or £520 to £950 per square metre of rooflight. The kerb formation, the glazing structure and the end details are the main cost drivers, and a continuous vault usually costs more per square metre than in-plane sheets but less than the same daylight in many discrete units.
This answer sits under our commercial skylight installation service. Barrel vaults price differently from in-plane replacement because they include the kerb and the weathering, not just a sheet. Our barrel vault and continuous rooflight installation page covers how they are built.
Budgeting per linear metre
Because a barrel vault runs along a bay as a continuous unit, the natural budgeting measure is the linear metre of run rather than the individual opening. The rate covers the vault glazing, the glazing bars, the insulated kerb and its weathering into the roof, and the fixings.
| Scope | Budget figure | Notes |
|---|---|---|
| Multiwall polycarbonate vault on new kerb | £600 to £1,400 per linear metre | Standard width, insulated kerb, normal hours |
| By rooflight area | £520 to £950 per m² | Includes kerb formation and weathering |
| Continuous rooflight run, per bay | £4,500 to £11,000 per bay | Bay width, run length and build-up |
| Glazed or framed vault upgrade | Add significantly | Framed glass systems for public-facing spaces |
| Integrated smoke or comfort vents | Quoted separately | Certified AOV assemblies add per unit |
Supply-and-fit for accessible roofs in normal hours. Access equipment, out-of-hours and coastal upgrades are added. Figures are for east of England budgeting.
The cost drivers
The kerb
The kerb is the biggest difference between a barrel vault and an in-plane sheet, and a real part of the cost. It lifts the vault above the roof plane, carries the insulation line up and over the opening, and weathers into the roof covering. On a flat or membrane roof it has to be tall enough to beat standing water, and insulated to avoid a cold bridge. Forming a continuous opening also removes structure, which has to be framed and supported. The kerb, its insulation and the structural framing are where a large share of the cost sits.
The glazing
Multiwall polycarbonate is the working choice for most industrial vaults, and the wall structure sets the price: more walls means a better U-value and more diffusion, at a higher cost. A framed glass vault, for a public-facing or office space, costs substantially more because of the framing, the sealed units and the safety glazing throughout. Our GRP, polycarbonate or glass page compares the materials.
The end details
Where a run ends, the vault has to be closed, weathered and drained, and these end details are a fixed cost per run regardless of length. A short run carries the same end-detail cost as a long one over fewer metres, so short runs price higher per linear metre. Longer runs spread the end-detail cost and drainage set-up over more metres and come down per unit.
Why length changes the rate. A barrel vault has fixed costs at its ends and in its kerb set-up that do not change much with length. A 6 metre run and a 20 metre run carry similar end and set-up costs, spread over very different lengths. So a longer continuous run is cheaper per linear metre than a short one, and a building that needs a lot of daylight is often better served by fewer long runs than many short ones.
Compared against discrete units
The alternative to a continuous vault is a number of discrete kerb-mounted rooflights or in-plane sheets delivering the same daylight. The comparison depends on how much daylight and what roof.
- Against in-plane sheets, a barrel vault costs more per square metre, because of the kerb and weathering. In-plane sheets are cheaper where a profiled metal roof just needs its daylight renewed. The vault earns its cost where more, even daylight is needed or the roof is flat or membrane.
- Against many discrete kerbed units, a continuous vault is often cheaper for the same daylight, because it forms one opening, one kerb line and one weathering detail rather than repeating the kerb and flashing around every unit. Many separate kerbs each carry their own set-up and weathering cost.
So the vault sits between: dearer than in-plane sheets, often cheaper than the same daylight in many separate units, and the right choice where the daylight need or the roof type calls for it. Our in-plane or kerb-mounted answer covers the wider comparison.
What it means around Ipswich
Barrel vaults suit the flat and membrane roofs found on some of the newer distribution and production buildings around the port and the A14 corridor, where there is no profile for in-plane sheets to match. On the coastal belt near Felixstowe, the kerb coatings and fixings take the marine upgrade. The self-cleaning curve is an advantage on any hard-access roof, holding its daylight with less cleaning, which matters on tall local sheds.
How much does a barrel vault rooflight cost?
As a budget figure, £600 to £1,400 per linear metre of run for a standard-width multiwall polycarbonate vault on a new insulated kerb, or £520 to £950 per square metre of rooflight, supplied and fitted on an accessible roof in normal hours. Longer runs come down per metre because the fixed kerb and end-detail costs spread over more length.
Is a barrel vault cheaper than lots of separate rooflights?
Often yes, for the same daylight, because a continuous vault forms one kerb line and one weathering detail rather than repeating the kerb and flashing around every separate unit. It costs more than in-plane sheets on a profiled metal roof, but where you need a lot of even daylight or the roof is flat, the vault is frequently the more economical route to it.
Get a barrel vault priced for your roof
We survey the roof, confirm the covering and drainage, and price the vault per run with the kerb, glazing and end details set out, so you can compare it fairly against in-plane sheets or discrete units.
Request a survey. Read across to cost per square metre, in-plane or kerb-mounted, and the barrel vault installation guide.
Thinking about this job? We survey across Ipswich, Suffolk and north Essex and give you a fixed price before any work starts, with a 10-year workmanship guarantee.