Roof type drives everything else in a commercial solar install — fixing method, mounting cost, structural loading, planning constraints, and whether the project is feasible at all. Our pre-contract survey opens with the roof, not the panels: get the roof right and the system specifies itself; get it wrong and you\'re looking at a re-roof, voided warranties, or an unbuildable design. This page covers every UK commercial roof type we encounter.
Why your roof type matters more than your roof area
The first conversation we have with every commercial customer is about roof type, not roof size. A 3,000 sqm asbestos cement warehouse roof can\'t take a single panel until the asbestos is removed; a 1,000 sqm modern standing-seam metal roof on a logistics shed is a 200 kW project that installs in two weeks. The difference is structural — solar PV typically adds 12-18 kg per square metre dead load, plus wind uplift design for UK weather, plus penetration or ballast considerations for waterproofing. Five questions we answer in the survey: what\'s the roof material, what\'s the structural loading capacity, what\'s the membrane life remaining, is there asbestos, and what\'s the fixing-method risk to roof warranty.
Profiled steel roofs — most common UK industrial
Profiled steel (often called trapezoidal or corrugated) is the standard modern industrial roof — used on warehouses, factories, logistics sheds, retail parks, and most post-1995 commercial buildings. It takes solar PV via clip-fix mounting systems from Schletter, K2 Systems, Renusol, and Mounting Systems. Clips wrap around or clamp onto the standing seam or trapezoidal profile without penetrating the metal sheet — meaning zero risk to roof waterproofing and zero impact on the existing warranty. Typical install density is 0.6-0.8 metres per kW. Structural loading is rarely an issue on modern steel-portal buildings designed for full snow load. Costs sit at the lower end of the per-kW range (£700-900/kW for systems above 250 kW). This is the easiest roof type to design for, and we install on profiled steel weekly.
Standing-seam metal — premium commercial
Standing-seam roofs (Kingspan, Kalzip, Tata Steel) are common on premium logistics, science parks, and post-2010 office buildings. They take solar PV via clip-fix to the seam — typically the S-5! system or equivalent. Zero penetration of the metal, retains the roof manufacturer warranty 100%, and installs faster than profiled steel because the seam clips don\'t need detailing. Per-kW cost is similar to profiled steel. Snow loading and wind uplift design are straightforward thanks to the engineered roof system. If your building is post-2010 with a standing-seam roof, your solar feasibility is essentially "yes" before we even survey.
Flat membrane roofs — TPO, EPDM, PVC
Most modern flat commercial roofs are single-ply membrane — TPO (Carlisle, GAF, Firestone), EPDM (Firestone RubberCover, Sika SikaPlan), or PVC (Sika Sarnafil, Soprema). These take solar PV via two routes:
- Ballasted systems (preferred). Concrete ballast blocks weigh down the array — no penetration of the membrane, no risk to roof warranty. Modern systems like the Schletter FixGrid, Mounting Systems Sigma EW, and Van der Valk East-West use east-west arrays at 10-15° tilt. Added structural load is 60-80 kg/sqm (including ballast) — needs structural engineer sign-off if the building wasn\'t designed for it. East-west arrays generate around 80-90% of south-facing kWh per kW but pack more kW onto a given roof area, so total annual generation is often higher than south-facing.
- Anchored systems (when ballast can\'t be used). Mechanical fixings through the membrane with proper waterproofing detailing — typically requires the installer to be approved by the membrane manufacturer to retain the roof warranty. We only fix-through when ballasting fails the structural check.
Older flat roofs with felt-and-bitumen membranes are a different conversation — typically over 15 years old, often near end-of-life, and re-roof + PV combined is the right answer.
Trapezoidal corrugated and asbestos cement — pre-1999 industrial
Mid-1990s and older industrial roofs frequently have asbestos cement sheet — typically Eternit Big-Six profiles, Marley, or Cape. Solar PV cannot be retrofitted to an asbestos cement roof under any circumstances: the Control of Asbestos Regulations 2012 prohibits drilling, cutting, or fixing anything to asbestos cement, and HSE guidance is unambiguous on this. The only legal route is a combined re-roof and PV install:
- Asbestos Management Survey (£400-900) to identify the exact materials
- Licensed asbestos removal contractor (HSE-licensed) to strip the sheet (£8-15/sqm)
- New profiled metal roof installed (£15-25/sqm)
- PV array installed on the new metal roof using clip-fix mounting
Combined cost: £25-35/sqm for the new roof plus £700-900/kW for the PV. The combined business case is usually better than expected because you\'re sharing scaffolding, project management, and access costs across both projects. The new roof has a fresh 25-30 year warranty, the PV qualifies for SEG and AIA, and the asbestos liability is removed permanently. Our most common 200-500 kW projects on older industrial estates are exactly this — combined re-roof plus PV. Read the HSE asbestos guidance for full regulatory detail.
Slate and tile roofs — heritage and smaller commercial
Slate and clay tile roofs are typical of hotels, schools, community buildings, listed-building offices, and pre-1960 commercial premises. PV mounting options:
- Through-tile fixings (BFV, Renusol RailUp): metal hooks slip under the tile and bolt through the rafter — the most cost-effective route, retains existing tiles. Listed buildings may not allow this.
- Tile-replacement integrated systems (Solarcentury C21e, GB-Sol PV slates, Marley SolarTile, Redland): replace specific tiles with PV-integrated tiles. Better aesthetic, higher cost (£200-300/kW more than through-fix). Often the only acceptable approach in conservation areas.
- In-roof systems (GSE Integration, Easy Roof, Viridian Clearline Fusion): the array is set into the roof at the same plane as the tiles, with flashings around the edge. Best aesthetic, premium cost, often used on listed-building approvals.
Listed buildings need Listed Building Consent — see our listed building solar panels guide. Conservation areas may need planning permission with Article 4 directions — see conservation area solar panels.
Concrete tile and modern commercial slate
Concrete and slate tile roofs on modern commercial buildings (pre-2005 retail, healthcare, leisure) take through-tile fixings or in-roof systems straightforwardly. No listed building or conservation constraints typically. Per-kW cost runs slightly higher than profiled steel (£900-1,100/kW) because of the longer install time per panel.
Roof condition assessment — pre-install survey
Every install above 50 kW gets a structural and condition survey at £600-1,500 (refunded against the contract). Survey checks: roof material identification, structural loading capacity (engineer\'s sign-off), membrane life remaining (ideally over 15 years), drainage detailing, plant penetrations causing shading, parapet wind effects, and asbestos register check. The survey output drives final design — and protects both parties from the surprises that kill commercial solar projects after contract signing. See our commercial solar survey guide for the full process.
Decision matrix — what your roof tells us about your project
| Roof type | Solar feasibility | Best mounting | Notes |
|---|---|---|---|
| Profiled steel | Excellent | Clip-fix (no penetration) | Easiest install, warranty retained |
| Standing seam metal | Excellent | S-5! clamp | Premium choice, fastest install |
| Flat membrane (under 10 yrs) | Excellent | Ballasted east-west | Structural check needed |
| Flat membrane (over 10 yrs) | Combined re-roof recommended | n/a | Replace membrane first |
| Slate or clay tile | Good | Through-tile fix or in-roof | Listed=consent |
| Asbestos cement | Re-roof required | Replace with metal first | Combined economics work |
| Concrete tile | Good | Through-tile or in-roof | Premium cost +£200/kW |
| Felt and bitumen (older flat) | Re-roof recommended | n/a | End-of-life membrane |
If you\'re unsure what your roof is, send us a postcode and we\'ll pull aerial imagery in the desk feasibility — most UK commercial roofs are identifiable from satellite plus a quick site visit if needed.
Common questions about commercial roof types
Can I install solar panels on an asbestos cement roof?
No — and it's the single most common reason a commercial solar project gets blocked. Pre-1999 industrial buildings often have asbestos cement (Eternit, Big-Six profiles) which cannot have anything fixed to it under HSE rules. The fix is a re-roof first: replace the asbestos sheet with profiled metal (£25-35/sqm including safe asbestos removal) and install PV on the new roof. The combined re-roof plus PV business case usually pays for itself; ignoring the asbestos and trying to install on top is illegal under the Control of Asbestos Regulations 2012.
What's the best roof type for commercial solar?
Profiled steel and standing-seam metal are the best — they take clip-fix mounting (no penetration), retain the roof warranty, and install fast. They're typical of modern industrial sheds, logistics warehouses, and post-2005 commercial buildings. Per-kW cost is at the low end (£700-900/kW for systems above 250 kW) and structural loading is rarely an issue. If your building has either of these roof types, solar PV is straightforward.
How do solar panels attach to a flat membrane roof?
Two routes. Ballasted — concrete ballast blocks weigh down the array, no penetration of the membrane, typical added load 60-80 kg/sqm (needs structural engineer sign-off). Anchored — mechanical fixings through the membrane with proper waterproofing detailing; risks the roof manufacturer's warranty unless the installer is approved by them. Most modern flat-roof systems on TPO or EPDM membranes are ballasted with east-west arrays for higher kWh per square metre. We'll only fix-through if the membrane manufacturer's approved-installer scheme covers us.
Will solar panels void my roof warranty?
It depends on the roof type. Clip-fix systems on standing-seam metal don't void the warranty — the panels attach to the seam, not the metal sheet. Ballasted systems on flat membranes don't void the warranty because there's no penetration. Through-fix systems on profiled steel or membrane roofs may or may not void the warranty depending on the manufacturer's approved-installer list. We'll always ask for and document this before contract signing.
What about slate or tile roofs on heritage commercial buildings?
Slate and tile roofs (typical on hotels, schools, listed-building offices, and community premises) take solar via through-tile fixings (BFV, Renusol RailUp), tile-replacement integrated systems (Solarcentury C21e, GB-Sol PV slates), or in-roof systems (GSE Integration, Easy Roof). For listed buildings, you'll likely need Listed Building Consent (see our listed building solar panels guide); for conservation areas, expect Article 4 directions and conservation officer review (see conservation area solar panels).
How much extra weight do solar panels add to my roof?
Roof-mounted solar PV typically adds 12-18 kg per square metre dead load (the panel itself, mounting rails, and fixings). Ballasted flat-roof systems add 60-80 kg/sqm because of the concrete ballast. Most modern commercial buildings designed to BS EN 1991-1-1 can take 12-18 kg/sqm easily; older buildings (pre-1980) may need a structural engineer's assessment before sign-off. We commission a structural survey on every install above 50 kW as part of the £600-1,500 pre-install package.
Can I install solar on a roof with under 10 years remaining life?
Technically yes, but it's usually a bad call. Solar PV systems have 25-year output warranties; if your roof needs replacing in year 8, you're paying to remove and reinstall the array (£8-15 per panel) on top of the re-roof cost. The smart economic call when membrane life is under 10 years is a combined re-roof + PV install — replace the membrane (£15-25/sqm typically) and add the PV at the same time, sharing scaffolding and access costs. Pays back faster than installing PV in isolation, and the new roof has a fresh 20-30 year warranty.