Most articles comparing standing seam and metal cladding are written for self-builders putting a roof on a barn. This one is for the people specifying roofs on warehouses, schools, distribution centres, sports facilities and commercial buildings, where the wrong call costs five or six figures to put right.
We’re commercial roofing contractors in London and the South East, installing both systems regularly, and the questions we get from architects, surveyors and facilities managers tend to be the same. This guide answers them with real project examples, real costs, and the things that actually matter when you’re specifying a metal roof for a commercial building.
The first question we ask every specifier: what’s the pitch?
Roof pitch is the single biggest factor in choosing between standing seam and metal cladding. Get this wrong and the spec falls apart before you’ve started.
Standard insulated metal cladding (composite sandwich panels and built-up systems) typically requires a minimum pitch of 10 degrees, depending on the manufacturer. Drop below that and you’re outside the warranty. Water sits at the laps. Capillary action pulls it back into the building.
Standing seam is different. Approved systems like AshZip and Kalzip can be installed down to 1 degree. The seam height and the rolled-and-zipped joint mean water can’t migrate sideways or backwards. That’s why standing seam dominates on low-pitch and architectural roofs where cladding simply doesn’t work.
But there’s a catch most specifiers miss. Even on a 1 degree standing seam roof, you need sufficient run-off length for water to actually escape. Get the falls wrong and you end up with standing water, which is a problem we’ll come back to.
When standing seam is the right call
We installed standing seam at Molesey Football Club after a failing composite sandwich panel roof had been pitched at around 3 degrees. The original system was outside warranty pitch. Water was finding its way through the end sheet laps via capillary action, dripping into the building below.
We replaced it with a standing seam roofing system designed for low pitch. Sheet lengths up to 14 metres in single runs, no end laps, no capillary failure points. Problem solved.
That’s the textbook case for standing seam:
- Pitch below 10 degrees
- Long uninterrupted runs needed
- Architectural visibility, with clean sightlines and no exposed fixings
- Premium finish required for the building’s appearance
When metal cladding wins
We recently completed an asbestos strip and replacement on a Luton warehouse. It was a distribution centre where downtime was the client’s biggest concern, and we specified composite sandwich panels rather than standing seam.
Three reasons:
Speed. Sandwich panels go up roughly twice as fast as standing seam. On a distribution centre, every extra week of roof works is operational disruption. Standing seam would have doubled the programme.
Internal finish. Sandwich panels arrive with a bright white liner pre-bonded to the underside. The client effectively got an internal ceiling at the same time as a new roof. Standing seam would have required a separate liner or insulated deck build-up.
Cost. On a 10-degree-plus pitch with no architectural requirement, sandwich panels deliver the same weather performance for less money.
That’s the textbook case for metal cladding:
- Pitch 10 degrees or higher
- Industrial or warehouse use where appearance is secondary
- Programme pressure where speed of install matters
- Need for an integrated internal liner finish
The costs nobody publishes
Most articles online quote material prices per sheet. That’s useless for a commercial specifier who needs an installed cost.
Here are the ranges we work to on UK commercial projects:
- Insulated metal cladding (composite or built-up): £140 to £180 per m² installed
- Standing seam: £190 to £220 per m² installed
The variance within each range comes down to specification, sheet thickness, insulation depth, number of details, rooflights, and access. The biggest cost driver on standing seam, and the one that surprises specifiers most, is penetrations.
The penetration problem on standing seam
Every penetration through a standing seam roof (vents, rooflights, soil pipes, plant) needs a welded or hot-air-welded flashing detail dressed around it. Done properly, it’s an excellent watertight solution. But it adds roughly £50 per linear metre of detail compared to the same penetration through cladding.
On a roof with twenty rooflights and a dozen plant penetrations, that adds up fast. We’ve seen specifiers price standing seam against cladding on a per-square-metre basis without factoring in penetrations, then watch the standing seam quote come back £20,000 higher than expected.
Cladding penetrations are dressed with EPDM collars, lead flashings or proprietary boots. Quicker, cheaper, more forgiving.
If your roof has a lot of penetrations, factor that into the comparison from day one.
Why life expectancy depends on the cut edges
Metal cladding typically comes with a 25-year manufacturer-backed warranty on the plastisol coating. Once the coating degrades, the bare steel underneath is exposed. Without intervention through spray-applied recoating or full replacement, corrosion sets in.
The detail almost every spec misses is cut edges.
When cladding is cut on site to fit around penetrations, eaves, ridges or verges, the cut exposes bare steel along the edge. If that edge isn’t sealed with a manufacturer-approved cut edge primer or paint, corrosion starts there and spreads. We’ve inspected roofs less than 10 years old where the entire underside was rust-bloomed at every cut line.
A spec that doesn’t mandate cut edge protection is a spec that’s halving the roof’s lifespan before the project even starts.
The standing seam failure mode most installers don’t talk about
Standing seam has fewer potential failure points than cladding once installed correctly. But “correctly” is doing a lot of work in that sentence.
Every standing seam system needs a fixed point, usually at the ridge or the gutter, with the rest of the sheet allowed to expand and contract through the seam clips as temperatures change. Aluminium moves significantly across a hot summer day and a cold winter night. If the fixed point is wrong, or if clips are over-fixed and prevent movement, the sheet stresses. We’ve seen aluminium splits and tears on roofs less than five years old where the installer didn’t understand the principle.
This is why manufacturer approval matters. Kalzip-approved or AshZip-approved installers are trained on the fixed-point principle and the clip-spacing rules. Generic metal contractors often aren’t.
A standing seam mistake we walked into
On one job, the main roof was at 2 degrees, fine for standing seam. But there was a smaller cut-away section behind a parapet detail that hadn’t been picked up at survey stage. Pitch was effectively flat. Standing seam went down across the whole roof.
Once installed, that flat section held standing water. In normal rain it drained eventually. In heavy rain, water tracked back behind the ridge closure and threatened to enter the building.
We stripped the section back and rebuilt the falls before it became a leak claim. The lesson: survey stage matters more than installation stage. Drone surveys with accurate pitch readings catch this. Walking the roof from one end doesn’t always.
Three things to tell a facilities manager comparing quotes
If you’re an FM looking at competing roofing quotes, three checks before signing:
Check the pitch is right for the system. Standing seam suits anything from 1 degree upwards. Cladding needs 10 degrees minimum. If a contractor is quoting cladding on a 6 degree roof, walk away.
Check the contractor is manufacturer-approved. Both Kalzip and AshZip publish lists of approved installers. The product is only as good as the installation. We’ve seen approved-system roofs fail at every penetration because the contractor cut corners on details, over-tightened cladding screws, or skipped safety fixings on rooflights.
Check the budget covers the system properly. Cladding sits at £140 to £180 per m² installed. Standing seam at £190 to £220. If a quote is significantly below these ranges, something is being missed, usually cut edge protection, penetration details, or fall correction.
The honest summary
Standing seam and metal cladding aren’t competing products. They solve different problems.
Standing seam wins on low pitch, architectural visibility, and long uninterrupted runs. Cladding wins on speed, cost, and roofs above 10 degrees with integrated liner requirements. The mistake is treating them as interchangeable.
The right answer for any commercial roof comes from the survey, not the spec sheet. Get the pitch checked properly, factor in every penetration, mandate cut edge protection on cladding, and use a manufacturer-approved installer for whichever system the building actually needs.
That’s how a commercial roof lasts 30 years instead of 15.
Exall Group are commercial roofing contractors based in Essex, working across London and the South East. Approved installers for Kalzip, AshZip, Sika, Soprema and IKO. Recent projects include works for Tesla, Rolex, BMW, the NHS and several UK universities.
