Asbestos and Fragile Roofs on Older Fabrication Units

Plenty of the best solar candidates in metal fabrication sit under the worst roofs. The single-shift, daytime load that makes a fabrication shop such a strong self-consumption case is often housed in a 1970s or 1980s portal-frame shed with a tired, corroded or asbestos-cement roof that no one has looked at closely in twenty years. That roof is exactly where the panels have to go, so it is the first thing a proper survey settles, not the last. Get it wrong and you either put a 25-year asset onto a roof with ten years left, or you disturb asbestos and turn a routine install into a notifiable incident. This guide walks through what an older fabrication roof needs before a single panel goes up.

Why older fabrication sheds are the problem cases

Fabrication has a longer building tail than most sectors. Sheet-metal shops, jobbing welders and sub-contract engineers frequently occupy older, cheaper units on trading estates precisely because the work is heavy, dirty and space-hungry, and the rent on a tired shed is lower. The result is a real cluster of pre-2000 roofs across the sector, and three recurring conditions:

• Asbestos-cement (AC) sheeting. Corrugated AC roof and wall sheets were standard on industrial buildings into the 1990s. They contain chrysotile (and sometimes amosite) bound in cement, and they are the defining problem roof for retrofit solar.
• Corroded single-skin steel. Un-insulated profiled steel sheet perforates from the inside out, especially over a humid, fume-laden fabrication environment. A roof that looks sound from the ground can be paper-thin at the laps.
• Fragile rooflights and liner panels. Old GRP rooflights go brittle and yellow, and degraded liner sheets on a built-up roof will not hold a person’s weight. Both are Work at Height hazards independent of the asbestos question.

None of this rules out solar. It just means the roof survey does real work before the electrical design starts, which is the opposite of how a generalist installer who has never worked a fabrication shed tends to run a job.

The asbestos duty comes first

Under the Control of Asbestos Regulations 2012, any building constructed or refurbished before the year 2000 must be treated as potentially containing asbestos, and the person in control of the premises has a duty to manage it. Before anyone fixes into the roof, that means an asbestos management survey at minimum, and a more intrusive refurbishment and demolition survey where the work will actually disturb the fabric, which fixing a solar array into or over a roof does.

The rule that catches most fabricators by surprise is simple: an asbestos-cement roof cannot take rooftop PV directly. You cannot drill it, walk it freely or hang a rail system off it. Drilling or cutting AC sheet releases fibres, and licensed or notifiable non-licensed work has strict controls. Even ballasted approaches are ruled out because AC sheet was never designed for the concentrated point loads a framed array plus wind uplift imposes, and because any maintenance access over the life of the array keeps putting people on a fragile, fibre-releasing surface.

So the honest position for a fabrication shop with an AC roof is that the roof deals with the asbestos first, then takes the panels. That is not a reason to walk away. It is usually the trigger for the single most sensible thing an owner of an old shed can do.

The HSE sets out the legal duty to manage asbestos in the government’s guidance on managing asbestos in buildings, and any survey must be carried out by a competent surveyor before works are specified.

Over-clad or re-roof, paired with the solar

Where a survey finds AC sheet or a corroded, fragile deck, the standard route is to over-clad or re-roof, and to do it as part of the same project as the solar. Two things make this pairing work rather than a cost blowout.

First, the timing is right anyway. A new PV array is warranted for 25 years, typically holding around 84 percent output at year 25, and mounting and DC cabling are rated for the same life. Most legacy fabrication roofs do not have 25 years left in them. Putting a quarter-century asset onto a roof with a decade of service remaining is a false economy, because you will be lifting the array to re-roof underneath it long before the panels are spent. Doing the roof at the point of install means one scaffold, one Work at Height campaign, and a roof and array that reach end of life together.

Second, the funding often folds into the project. Approaches include:

Route	How the roof gets funded
Over-cladding	A new insulated (typically composite) sheet is fixed over the existing roof on a spacer system, encapsulating the old AC or corroded deck, with the array mounted on the new outer skin. Often the lowest-disruption option.
Full re-roof (asbestos removed)	Licensed removal of the AC sheet and a new roof installed, then the array. Higher cost and disruption but resets the whole roof.
Combined finance	Asset finance or a Power Purchase Agreement structured over the system life can carry the roof works alongside the PV, so the combined cost is spread and often cash-flow positive against the energy bill it replaces.

Over-cladding is frequently the pragmatic answer on a fabrication shed: it encapsulates the asbestos in place rather than removing it, adds insulation to a previously un-insulated single-skin roof (a genuine bonus for a shop that runs cure ovens or fights winter heat loss), and gives a clean, warranted outer skin for the panels. Which route is right depends on the survey, the sheet condition and the budget, and our cost breakdown shows where roof works sit against the array spend, while the grants and funding page covers the capital-allowance and PPA routes that can carry both.

Fragile roofs and Work at Height, even without asbestos

Asbestos is not the only reason an older fabrication roof is dangerous. Under the Work at Height Regulations 2005, a fragile surface is one that will not safely bear the weight of a person and any load they carry, and a great many old fabrication roofs qualify: brittle GRP rooflights, degraded liner panels, thin corroded steel and, of course, AC sheet itself. Falls through fragile roofs remain one of the biggest killers in construction.

For a solar install this shapes the whole method. A framed PV array adds roughly 15 to 25 kg per square metre of dead load plus wind uplift, so the deck has to carry both the array and the people fixing and maintaining it. On a legacy shed that means:

• A structural engineer confirms the portal frame and roof can carry the array before the design is fixed, with any EOT crane-rail and gantry dead loads deducted from residual capacity first.
• Fragile-roof precautions under CDM 2015 are planned in: staging, running boards, edge protection and rooflight covers, so no one relies on a fragile surface bearing weight.
• The fabricator, as the CDM Client, provides pre-construction information on the roof, the asbestos register and any live process risks below, and appoints a Principal Designer and Principal Contractor in writing.

This is where fabrication experience earns its keep. A workshop is a live, hazardous environment below the roof line, with welding, hot work, overhead crane movements and extraction stacks all in play, and the roof works have to be sequenced around production. The structural roof-loading and survey question is covered in more depth in our FAQs, and the self-consumption case for single-shift fabrication explains why these older sheds are worth the roof effort in the first place.

What the survey settles before you commit

The point of doing all of this up front is that the fabricator knows the full picture before spending anything, not after the scaffold is up. A competent pre-install assessment on an older unit should return clear answers on:

• Asbestos. Management survey (and R&D survey where the roof will be disturbed); AC sheet identified, registered and a route agreed (encapsulate by over-cladding, or licensed removal).
• Roof condition and life. Corrosion, laps, fixings and remaining service life, and whether the roof outlives the 25-year array or needs replacing with it.
• Structure. Portal-frame and purlin capacity for the array dead load plus uplift, with crane-rail loads deducted.
• Fragility and access. Rooflights, liner panels and safe access and maintenance routes for the life of the system.
• Fixing method. Whether the sound roof can be rail-fixed or clamped, or whether an over-clad new skin is the fixing substrate.

Handled properly, an old asbestos or corroded roof is not a dealbreaker for fabrication solar. It is a fork in the road that usually leads to a better outcome: a new, insulated, warranted roof and a 25-year array installed together, funded as one project, on a shed that was going to need the roof done anyway. If you want that assessment on your unit, our team can start with the roof, so request a feasibility survey and quote and we will tell you honestly what your roof needs before a panel goes anywhere near it.