A roof survey for commercial solar should answer four questions. Can the structure carry the extra weight and wind load? Is there asbestos? How long will the roof covering last? And which fixing method suits this roof? The answers should come in a written report with calculations and photographs, ending in a clear yes, no or “not yet”.
An installer’s free survey is a different thing, since it exists to size a system and write a quote. An independent roof survey exists to find out whether you should proceed at all. It is the stage most likely to turn a promising roof into a “no”, so it pays to know what a good one contains before you commission it or accept one.
Why structural capacity can decide the whole project
Panels, rails and any ballast are permanent weight. A commercial roof was designed with a limited margin for that, after its own weight, fixed services and the wind and snow it must resist. If the margin is gone, the roof needs strengthening before anything is fixed to it. That cost can wipe out the saving.
Older buildings carry extra uncertainty, because purlins corrode and sheets sag. Someone may have cut a hole for plant ten years ago and never told the engineers. Drawings, where they exist, show the roof as designed, not as it stands today.
Guidance exists for this exact check. The Institution of Structural Engineers has published advice on assessing existing roofs before adding solar panels in its journal. Read it as a sign that the check is skilled work, not a box to tick.
What the MCS standard does and does not cover
Many people assume the MCS installation standard settles the structural question, yet it only partly does. The MCS standard for solar PV installation, MIS 3002, covers systems up to 50 kWp DC. Most commercial roof arrays are larger than that, so the standard is not the safety net you might expect.
Where it does apply, it asks for a competent person to check the roof can take the added load. Trade commentary on the current version reports that a structural engineer is needed for unusual roofs. Examples include roofs altered after construction, low-pitched roofs and ballasted systems. The same commentary notes that the standard says a check must happen but not what it must contain.
So for a commercial roof, set the bar yourself. Ask for a named, qualified person, the loads they checked, and the margin they found.
Ballast, bolts and the fixing decision
There are two broad ways to hold panels on a roof. Mechanical fixings go through the roof covering into the structure. Ballasted systems sit on the roof and use weight to resist the wind. Ballast adds load but keeps the membrane intact.
Neither is better in general, because the choice depends on spare capacity, roof type and wind exposure. That is why it belongs in the survey. If the roof has little spare capacity, heavy ballast is out. If the covering is near the end of its life, you may not want holes in it.
Ask the surveyor for the actual added load per square metre of the proposed layout, taken from the manufacturer’s data for that system. Do not accept a “typical” figure from a brochure.
Asbestos: the check you cannot skip on an older roof
Asbestos was widely used in building materials until it was banned. The Health and Safety Executive (HSE) says that using asbestos in building work has been illegal since 1999, and that asbestos cement roofing is among the common materials found in older buildings. A warehouse or factory with a profiled sheet roof from before 2000 deserves suspicion until tested.
The law puts a duty on whoever maintains or controls the building. Under regulation 4 of the Control of Asbestos Regulations 2012, that person must assess whether asbestos is or may be present, record it and manage the risk. The duty covers the whole building, roof included, and any contractor who works on it needs that information first.
Two survey types matter, as set out in HSE’s survey guide HSG264:
- A management survey locates and records asbestos for day-to-day management of an occupied building.
- A refurbishment and demolition survey is intrusive and is needed before work that disturbs the fabric.
An existing management survey is a useful start. It may not cover the roof area where fixings will go, or the way the work will disturb it. Ask your asbestos surveyor which type the installation needs and whether the roof and any plant platforms were included.
HSE also explains that removing asbestos cement sheeting that will be substantially damaged or broken up is notifiable work. Finding asbestos mid-installation stops work. Finding it at survey stage lets you price removal, or choose a ground-mount instead.
Roof covering life
A solar array should outlive the roof under it, or be built so it can be lifted for re-roofing. If the covering has seven years left and the array should run for twenty-five, you will pay to remove and refit the panels once. Plan for that cost in the model, or re-roof first.
The survey should say what condition the covering is in, what repairs are due, and whether the manufacturer’s warranty on the roof allows fixings or ballast.
Working at height
Roof work is hazardous in its own right. HSE’s provisional figures for 2025/26 record 31 workers killed in falls from height, around a quarter of all work deaths in Great Britain, the leading cause. A survey that relies on aerial photographs alone misses defects. A survey done on site must be done by a competent, insured person with proper edge protection.
What the written report should contain
Use this as a checklist when you commission the work or review someone else’s.
| Section | What it should show |
|---|---|
| Structural assessment | Condition of purlins, trusses and sheets, signs of corrosion or sagging, and the spare capacity found |
| Load check | The added load of the proposed system against wind and snow demands for the site |
| Asbestos | Survey type held, materials found or presumed, and any work needed before the roof is touched |
| Roof covering | Remaining life, repairs due, and warranty position |
| Fixing method | Mechanical or ballasted, and the reasons |
| Photographs | Dated images of defects, obstructions and access routes |
| Conclusion | A written go, no-go or conditional go, with the conditions listed |
A report that says only “the roof looks sound” is not due diligence. Lenders, insurers and boards expect to see calculations and a named author.
Where the roof survey sits in the wider process
The roof survey is one part of a feasibility study, which also covers shading, yield, grid headroom and payback. Our guide to what a commercial solar feasibility study involves sets out the full sequence.
If the roof fails, solar may still work elsewhere on the site. See ground-mount versus rooftop solar for how to compare the two. If the roof passes and you are ready to buy, the due diligence checklist for a solar contract covers the installer’s paperwork. For timing once approvals are in place, see how long commercial solar installation takes.
We do not install or sell panels. When we run a feasibility study, the surveys are commissioned for your benefit, and the report is written to stand up in front of a lender or an insurer.
A roof check is the first gate, because a weak roof ends the project. Our feasibility studies include it. Energy and ROI modelling adds roof repair to the case, while procurement and tender support puts survey duties into the specification. Across many buildings, portfolio optimisation ranks roofs by condition.