Steel-clad portal-frame buildings — general-purpose sheds, grain stores, livestock housing, machinery stores — make up most of the roof area on a modern farm, and they suit solar well: big, simple, often low-pitched, with purlins at regular spacing. The panels themselves are not heavy. A current 450–475 W module weighs 21.0 kg and measures 1,762 × 1,134 mm, which is about 10.5 kg per square metre (roughly 0.10 kN/m²) before rails and fixings. The questions that decide a metal-roof project are how the kit attaches to the sheet, whether the sheet and its own fixings can take the extra wind uplift, and whether the roof will outlast the array.
How panels are fixed to each type of metal roof
| Roof sheet | Usual fixing method | Points to check |
|---|---|---|
| Box-profile (trapezoidal) | Short rails or rail-less mounts fixed to the crowns of the ribs with sealed screws or rivets, or fixings taken through to the purlins | Sheet thickness and the sheet's own fixings; sealing at every penetration |
| Corrugated | Brackets fixed through the top of the corrugation into the purlins, with EPDM sealing washers | Purlin spacing and condition; older sheets may be corroded at the laps |
| Standing seam | Clamps that grip the raised seam with set screws, without piercing the sheet | The seam profile must match the clamp; confirm it with the roof manufacturer |
| Insulated (composite) panels | Only the roof manufacturer's own PV system and fixings — for example, one major system fixes only into the panel's central crowns, never the side laps or rooflights | Substitute fixings can void design calculations and warranties; structural approval first |
Based on published product information from K2 Systems, Renusol, Van der Valk, S-5! and Kingspan (PoweRail RW installation guide, August 2024). Asbestos-cement sheets are a different case — see solar panels on asbestos roofs.
MCS 012: the standard for the mounting kit
MCS 012 is the product standard for the kits that fix solar panels to a roof. Issue 3.0 (May 2023) tests a kit for wind uplift, fire performance and weathertightness against wind-driven rain, and lists profiled, corrugated and standing-seam metal sheet among the roof types a manufacturer can declare. Product certification to it has been mandatory since May 2025.
For systems installed under MCS — the certification scheme that covers systems up to 50 kWp — the installation standard (MIS 3002) requires an MCS 012-certified kit on pitched roofs. A non-certified kit is allowed only with structural and wind-load calculations, evidence of weathertightness and compatibility, and a note to the customer to update their fire risk assessment. On a larger farm system outside MCS, ask for the same evidence anyway; your insurer is likely to.
What the roof has to be checked for
The current MCS installation standard (MIS 3002 version 6.0, mandatory from June 2026) sets out checks that make sense on any farm roof:
- The structure must be checked by a suitably competent person — and by a qualified structural engineer if the roof is unusual: signs of distress, later alterations, a pitch under 30°, or features that trap snow.
- The sheet and its fixings: where brackets are screwed into metal cladding, the sheet must be thick enough for the brackets and screws and able to take the extra wind uplift, and the sheet's own fixings must be able to carry the loads through to the structure.
- Low-pitch roofs: the standard treats a roof under 10° as flat, which brings flat-roof rules, including pull-out tests on fixings. Many portal-frame sheds are close to that pitch.
A low-pitch roof also changes the output: on PVGIS, a 10° roof near York generates about 868 kWh per kWp a year against 960 on a 30° roof. Our farm solar cost guide covers what that means for the numbers.
Will the roof outlast the array?
This is the question that catches farms out. Fire-safety guidance for PV (RC62) assumes a design life of 30 to 35 years, and the BRE National Solar Centre's good-practice guide advises doing any roof repair or replacement before or with the solar installation. Removing and refitting an array to re-sheet a roof in year ten costs money and output.
Steel sheet guarantees vary widely by product and use. Tata Steel's Colorcoat HPS200 Ultra carries a Confidex guarantee of up to 40 years on the outer face for industrial and commercial buildings, and since October 2023 Tata has offered a guarantee addendum for PV installations — though not for sheets already on a roof. Its Colorfarm sheet for agricultural buildings carries a 20-year internal performance guarantee, provided the building is well designed and ventilated. So find out what your sheets are, how old they are and what their guarantee says before you commit — corroded laps, failed fasteners or a guarantee near its end are reasons to re-sheet first.
Fragile rooflights: the biggest safety risk
Farm roofs kill people. HSE's guidance for agriculture says that "In agriculture, roughly half the deaths and serious injuries caused by falls involve work on fragile roofs", and that "Roof lights will often also be fragile." It adds a warning that fits many farm sheds: "Fragile roof-light sheets can often be found in roofs which are otherwise non-fragile."
The law is clear. Regulation 9 of the Work at Height Regulations 2005 requires every employer to ensure "that no person at work passes across or near, or works on, from or near, a fragile surface where it is reasonably practicable to carry out work safely … without his doing so". Ask any installer how they will access the roof, protect the rooflights while they work, and whether permanent protection over skylights is part of the design — the MCS standard asks installers to consider it. Rooflights under an array can also be shaded, so plan the layout around them.
Fire safety on farm buildings
RC62, the insurers' recommendations for fire safety with PV installations, is written for commercial buildings but reads as though it had farms in mind. Among its points: a PV system should not reduce the roof's fire rating, and non-combustible roofs are preferred; modules should be kept back from fire walls (2.5 m either side, or 1.2 m where the risk is low); grain barns at harvest time can hold explosive dust atmospheres that must be assessed; cables should be protected from rodents with armoured cable or sealed trunking; and firefighter DC isolation should be fitted where wiring rules or the insurer require it. Tell your insurer about the installation before it goes ahead — straw, hay and fertiliser stores raise the stakes.
Livestock buildings, coasts and planning
Over livestock, ammonia is the extra hazard for the panels themselves: look for modules tested to IEC 62716, and to IEC 61701 for salt mist on coastal holdings — see agricultural solar panels. For planning, panels on a farm building's roof in England are normally permitted development under Class J, provided they stand no more than 0.2 m proud of a pitched roof and at least 1 m from the edge, with prior approval on design and glare above 50 kW; Scotland, Wales and Northern Ireland have their own rules. Our guide to planning permission for farm solar has the detail, and solar panels on farm buildings covers the wider project.
Solar panels on metal roofs — frequently asked questions
Can you put solar panels on a metal roof?
Yes — metal-clad farm buildings are among the easiest roofs to fit. The mounting kit is chosen for the sheet profile: short rails or rail-less mounts on the ribs of box-profile sheet, brackets through the crown into the purlins on corrugated sheet, or clamps that grip the seam without piercing it on standing-seam roofs. The roof structure, fragile rooflights and the remaining life of the sheets all need checking first.
How much weight do solar panels add to a metal roof?
About 10.5 kg per square metre for the panels alone, using a current 450–475 W module (21.0 kg, 1,762 × 1,134 mm), plus the rails and fixings. That is roughly 0.10 kN/m². Whether a particular roof can take it — including extra wind uplift at the fixings — is for a competent person or structural engineer to check.
Do solar panels on a metal roof need MCS-certified mounting?
For MCS installations on pitched roofs, the mounting kit must be certified to MCS 012, the standard that tests kits for wind uplift, fire and weathertightness. A non-certified kit is allowed only with structural and wind-load calculations and evidence of weathertightness and compatibility.
Are farm roof lights a problem for solar installation?
They are a safety issue. HSE says roof lights will often be fragile, and that fragile roof-light sheets are often found in roofs that are otherwise non-fragile. In agriculture, roughly half the deaths and serious injuries caused by falls involve work on fragile roofs, so the installer must plan how they will be protected during and after the work.
Should I replace an old metal roof before fitting solar?
If the sheets are likely to need replacing within the life of the array, usually yes. Fire-safety guidance for PV expects a design life of 30 to 35 years, and the BRE National Solar Centre advises doing any roof repair or replacement before or with the solar installation — lifting and refitting panels later adds cost.
Sources
- MCS — MCS 012 Solar Mounting Standard (Product), Issue 3.0; MIS 3002 Solar PV Systems, version 6.0 (clauses 5.5.2, 5.5.5, 5.6.2, 5.9.4–5.9.12).
- HSE — Agriculture: falls from height and fragile roofs (July 2024). Work at Height Regulations 2005, regulations 2 and 9 (legislation.gov.uk).
- Fire Protection Association / RISCAuthority — RC62, Recommendations for fire safety with PV panel installations, version 2 (2023).
- BRE National Solar Centre — Solar roofs: good practice guide (2016).
- Tata Steel UK — Colorcoat HPS200 Ultra and Colorfarm product pages; PV guarantee update (October 2023).
- Kingspan — PoweRail RW installation guide (2nd issue, August 2024); K2 Systems, Renusol, Van der Valk and S-5! product pages.
- Trina Solar — Vertex S+ TSM-NEG9R.28 datasheet (2026). PVGIS v5.3 (EU Joint Research Centre), York.