The mounting system is the structural interface between solar panels and your roof — and the single biggest determinant of whether the install will hold for 25 years and whether it will void your roof warranty along the way. Roof type drives mounting choice, not the other way around. This page covers every commercial roof type we routinely encounter (standing-seam metal, profiled steel, flat membrane, trapezoidal corrugated, asbestos cement, tiled), the matched mounting systems and brands we specify, the ballast-versus-penetration trade-off on flat roofs, wind and snow load calculations, tilt angle decisions, and ground-mount and solar carport options for sites where rooftop is unsuitable.
Why roof type drives mounting choice
Every commercial roof has a specific structural geometry that defines what mounting systems will work. A standing-seam metal roof has continuous folded seams that act as natural attachment points — clip-fix mounting grips the seam without any penetration. A profiled steel roof has corrugated peaks and troughs — through-fixed mounting penetrates the trough with weather-sealed brackets that bolt into the underlying purlins. A flat membrane roof has a continuous waterproof skin and either no structural fixing points (forcing a ballasted approach) or sound sub-deck (allowing anchored brackets through the membrane). The wrong mounting on the wrong roof either fails structurally, voids the roof warranty, or both.
Our survey identifies the roof type, sheet condition, fixing method and structural margin before we specify any mounting system. The mounting choice is documented in the survey output and forms part of the fixed-price proposal. See our commercial solar survey page for the assessment scope.
Standing-seam metal roofs
Standing-seam (sometimes called "secret-fix" or "snap-lock") metal roofs are the easiest commercial roof type for solar mounting. Common on modern (post-2005) industrial buildings, distribution centres and supermarkets. The mounting solution is clip-fix: clamps grip the upstanding seam between sheets, with no penetration of the roof skin. Result: no risk to roof warranty, fast install, low risk of leaks long-term.
Brands we routinely specify for standing-seam: Schletter Standard Rapid system, K2 Systems SingleHook S-Dome, Renusol VarioStand standing-seam clamps. Per-panel mounting cost is typically £25-£45 in 2026 — at the cheaper end of commercial mounting. Install is fast (one experienced fitter can mount 40-60 panels per day on a clean standing-seam roof), low disruption and low waste.
Profiled (corrugated) steel roofs
Profiled steel — sometimes "trapezoidal" or "box-rib" — is common on industrial buildings of all eras. The most common UK profile is 32/1000 (32 mm rib height, 1000 mm cover width) or similar variants. Mounting solution is through-fixed: brackets bolt through the trough into the underlying purlins, with weather-sealed brackets and EPDM sealing washers. Penetration carries some warranty risk on the underlying roof, but with modern brackets and 25-year sealant the long-term leak risk is low.
Brands we routinely specify for profiled steel: Renusol VarioRoof System (very strong on UK trapezoidal profiles), Mounting Systems Quickline-Trapezsheet, Schletter ProfilEnergy. Per-panel mounting cost is typically £30-£55. Install moderate speed (30-45 panels per day per fitter — the through-fixing slows things down). Critical detail at design stage: check the purlin spacing matches the bracket spacing, otherwise additional bracketry or alternative fixing patterns are needed.
Flat membrane roofs (ballasted vs anchored)
Flat roofs — typically single-ply membrane (TPO, EPDM or PVC) on a structural deck — are the most varied category for mounting choice. Two competing approaches: ballasted (system sits on the roof surface, held by weight) and anchored (through-membrane brackets penetrate the structural deck below).
Ballasted systems use either trays filled with concrete blocks, sand or gravel, or rail systems with concrete ballast at intervals. No roof penetration so no warranty risk on the underlying membrane — popular with property owners who want to preserve the roof warranty. Trade-off: added weight (10-30 kg per square metre depending on wind exposure) requires structural confirmation, and the mounting system itself is heavier and more material-intensive. Brands we specify: Schletter Fix-Z (low-rise ballast), Mounting Systems Sigma EW (east-west ballasted), Van der Valk East-West (Dutch-engineered, very mature on UK commercial flat roofs). East-west ballasted systems with panels back-to-back at 10 degrees pack the roof tighter than south-facing systems — typically 12-15 panels per 10 square metres versus 8-10 for south-facing. Per-panel mounting cost is typically £40-£70.
Anchored systems use brackets that penetrate the membrane and bolt into the structural deck or pre-installed mounting rails, with the membrane re-sealed using manufacturer-rated boots. Lower weight than ballasted (no concrete required), but penetration risk to the membrane warranty. Brands: Schletter, K2 Systems flat-roof anchored variants, Renusol. Suitable where the roof structure cannot take ballast loading or where ballast height creates planning or aesthetic issues.
Trapezoidal and corrugated variants
Older corrugated profiles (typical on 1970s-90s industrial buildings) and unusual profiles need specific clamps. Renusol's TrapezSolid range and Mounting Systems' modular trapezoidal products cover most UK profiles. The critical survey detail: identify the exact profile (manufacturer, rib height, cover width) at survey stage so the right clamp is specified. Generic clamping on a trapezoidal profile risks long-term water ingress around the bracket.
Tile roofs (heritage installs only)
Tiled roofs are common on commercial heritage buildings (offices in Victorian terraces, listed buildings, schools in older properties). Tile mounting uses through-tile hooks: a bracket clips under the tile and bolts into the underlying batten. No penetration of the tile face. Brands: K2 Systems CrossHook, Schletter Eco05 tile hook. Per-panel cost typically £45-£75 — slower install due to per-tile careful work. We typically only do tile installs on commercial buildings with no flat-roof or industrial-roof alternative, and we always confirm with the customer that tile damage during install is the customer's risk (we minimise but cannot eliminate).
Asbestos cement roofs
Pre-2000 buildings often have corrugated cement sheeting containing asbestos. Two paths for solar: roof replacement first (typically £15-£60 per square metre plus disposal — adds 4-8 weeks but produces a 25-year-life roof afterwards), or solar install on the existing asbestos with non-penetrating mounting (specialised clamp systems that grip the corrugation without disturbing the sheet, agreed in writing with an HSE-licensed contractor with method statements).
For most commercial customers with an asbestos roof, we recommend the roof replacement path — solar on a roof with under 10 years of life left is bad maths, and the asbestos remediation can sometimes be partially funded through grants or insurance settlements. Where the customer chooses to install on the existing roof, we work with HSE-licensed asbestos contractors and never proceed without a written method statement.
Ground-mounted solar
Where rooftop solar is impractical (small roof, structural concerns, asbestos roof with no remediation budget) or where land is available, ground-mounted systems are an option. Mounting uses driven steel piles or screw-pile foundations, with rail-and-clamp panel mounting on top. Schletter Schletter G-Max, Mounting Systems M-Strong are common ground-mount kits. Tilt is set at site latitude minus 10 degrees for best annual yield (typically 25-35 degrees in UK). Per-kW cost is similar to good rooftop installs but planning permission and land use considerations apply. See light industrial units and factories sector pages for ground-mount applications.
Solar carports
Solar carports are dual-use steel canopy structures providing shade for parked vehicles plus solar generation. Typical commercial applications: customer car parks at retail, hotel and leisure sites, employee car parks at offices and industrial sites. Carport mounting is purpose-engineered: bespoke steel frame with integrated rail-and-clamp panel mounting. Tilt typically 10-15 degrees for aesthetic and weather-shedding reasons. Per-kW cost is materially higher than rooftop (typically £1,300-£1,800/kW versus £900-£1,200/kW rooftop) due to the steel structure cost — but the secondary value of vehicle shading and EV charging integration often justifies it. See our solar carports sector page for full carport-specific design considerations.
Wind and snow load calculations
Every commercial mounting system specification includes wind and snow load calculations to BS EN 1991-1-4 (wind) and BS EN 1991-1-3 (snow). Wind loading is the dominant force in most UK locations — coastal sites face significantly higher wind exposure than inland sites and need higher ballast or stronger anchoring. Snow loading matters at elevation (Pennines, Highlands) and on shallow-tilt installations where snow accumulates.
The wind load calculation drives the ballast quantity on flat-roof systems and the anchor density on through-fixed systems. We use manufacturer-supplied design tools (Schletter PV-Calc, K2 Base, Mounting Systems CONFIG) cross-checked against site-specific exposure data from the BS EN 1991 wind atlas. The output is a mounting plan with ballast positions, anchor positions and associated structural loadings — this goes to the structural engineer for sign-off before order.
Bifacial panel considerations
Bifacial panels (which generate from both faces) need extra mounting height — typically 10-25% additional ground clearance to allow rear-side light to reach the back face. On flat roofs this means raised ballast systems or higher tilt. On ground-mount, taller piles. Bifacial gain in UK climate is typically 5-12% above mono-facial — modest but worth pursuing on optimal mounting. Albedo (reflectivity of the surface beneath) matters: white membrane roofs and concrete ground deliver more bifacial gain than black asphalt.
Useful authority links
BS EN 1991 wind and snow load standards are at BSI. HSE asbestos guidance is at hse.gov.uk/asbestos. MCS-certified installation standards are at mcscertified.com.
Related decision pages
For the survey work that drives mounting choice see commercial solar survey. For sector-specific roof types and mounting see warehouses, factories, cold storage, solar carports, light industrial units, offices, retail showrooms. For project programme see installation timeline. For inverter selection that pairs with the mounting system see best commercial solar inverters. For warranty implications of penetration choices see commercial solar warranty. The hub for everything commercial solar is commercial solar PV.
Solar mounting — common questions
Do solar panel mounts penetrate the roof?
It depends on the roof type. Standing-seam metal roofs are clip-fixed (no penetration — clamps grip the seam). Profiled steel roofs are typically through-fixed (penetration with weather-sealed brackets). Flat membrane roofs use either ballasted (no penetration, weighted) or anchored (penetration with sealed brackets) systems depending on roof condition and wind loading. Trapezoidal corrugated roofs use specific clamps designed for the profile. Penetration carries a risk of voiding the original roof warranty — we always check with the customer before specifying a penetrating system.
What is the additional roof load from a commercial solar installation?
Typical added dead load is 12-18 kg per square metre for the panel and mounting system on a rooftop install. Ballasted systems on flat roofs add a further 10-30 kg per square metre depending on wind loading calculations. The structural assessment in our survey confirms the existing roof can take this additional load — most modern profiled steel and standing-seam roofs have ample design margin; older buildings sometimes need targeted strengthening. Wind uplift forces are calculated separately to BS EN 1991-1-4 and contribute to the mounting system selection.
What mounting brands do you specify?
For UK commercial work we routinely specify Schletter (German engineering, broad product range, very strong on flat-roof systems), K2 Systems (German, strong on standing-seam metal and profiled steel), Renusol (German, particularly strong on trapezoidal corrugated), Mounting Systems GmbH (German, strong on ballasted flat-roof and ground-mount), Van der Valk (Dutch, strong on east-west ballasted flat-roof systems). We pick by roof type and project requirements rather than by default brand.
What is the difference between ballasted and anchored mounting on a flat roof?
Ballasted systems sit on the roof surface and are held in place by their own weight — typically concrete blocks or sand/gravel-filled trays. No roof penetration so no warranty risk on the underlying roof, but adds weight (10-30 kg per square metre) and requires structural confirmation the roof can take the load. Anchored systems use through-roof brackets that penetrate the membrane, sealed with manufacturer-rated weatherproof brackets. Lower weight, no ballast required, but requires roof penetration. Choice depends on roof condition, structural margin, wind exposure and customer preference on warranty risk.
What tilt angle is best for commercial solar in the UK?
For pitched roofs the panel follows the roof pitch — typically 15-35 degrees on UK commercial buildings. For flat roofs we usually specify 10-15 degrees for ballasted systems (lower wind loading, more panels per square metre) or 20-30 degrees for high-yield optimisation where roof loading allows. East-west configurations (panels back-to-back at 10 degrees) maximise panels per square metre at the cost of about 5-7% per-panel yield versus optimal south-facing tilt. We model both options in PVSyst at design stage.
Are there mounting systems that work on asbestos cement roofs?
Yes — non-penetrating clamp-fix systems (typically clamping over the corrugation profile) avoid disturbing the asbestos sheeting. Specialised drilling protocols with HSE-licensed contractors can also be used where penetration is required. We work with HSE-licensed asbestos contractors and always get a written method statement before any solar work proceeds on an asbestos roof. Most commercial sites with asbestos roofs are best served by replacing the roof first — both because solar on a 25+ year-old failing roof is bad maths and because asbestos remediation grants are sometimes available.
What about ground-mounted solar and solar carports?
Ground-mount mounting (typical for ground-mounted solar farms or large brownfield commercial sites) uses driven steel piles or screw piles into the ground, with rail-and-clamp panel mounting on top. Schletter and Mounting Systems both make ground-mount kits. Solar carports use steel canopy structures with integrated rail-and-clamp mounting — typically purpose-engineered for the specific site rather than off-the-shelf kit. Our /sectors/solar-carports/ page covers carport-specific design.