How to Commission a Structural Survey for Solar PV: A Step-by-Step Guide for Project Teams

Commissioning a structural survey for commercial solar PV is straightforward once you understand what you need to specify, what data to gather before instruction, and what to expect from the process. Without that understanding, the commissioning process is often slower and more friction-filled than it needs to be, with project teams providing insufficient data, receiving reports in formats that need reworking, or commissioning the wrong product for the building concerned.

This step-by-step guide is written for project managers, EPC contractors, asset managers, and developers who are commissioning structural surveys for the first time or who want to optimise a process they have found inefficient. It covers the key decisions, the data required at each stage, what to specify when placing the instruction, and how to review and use the report once received.

Step 1, Determine Whether You Need a Desktop Report or an On-Site Survey

The first decision when commissioning a structural survey is the product type. Desktop structural reports and on-site structural surveys are both valid pre-installation engineering assessments, but they are appropriate for different buildings. Using the wrong product for the building wastes money and time.

A desktop structural report is appropriate for most standard UK commercial and industrial buildings constructed after 1970. Steel portal frame warehouses, light industrial units, modern logistics buildings, retail units, and office buildings in this vintage range are typically assessable by desktop methodology. If structural drawings are available, the desktop assessment is highly reliable. If drawings are not available, the assessment can still proceed for standard typology buildings using conservative benchmarks.

An on-site structural survey is appropriate where desktop assessment cannot reach a reliable conclusion: pre-1960 buildings, non-standard or hybrid construction, buildings with no drawings and atypical structural characteristics, buildings with reported structural issues or modifications, or buildings where the desktop assessment identifies loading at or near the structural capacity margin.

When in doubt, start with a desktop assessment. Most reputable structural engineering firms offering desktop reports for commercial solar will flag, as part of their assessment process, whether the building is within the scope of reliable desktop assessment or whether on-site survey is required. A desktop referral to on-site survey is not a wasted cost, it gives you technical justification for the on-site commissioning decision and a brief for what the on-site survey needs to resolve.

Step 2, Gather Your Data Package Before Instruction

The quality of a structural survey output, and the speed at which it is delivered, depends on the quality of the data provided with the instruction. Assembling a data package before submitting the instruction removes the data-gathering lag from the engineer's delivery timeline.

For a desktop structural report, the ideal data package includes: the site address and postcode; structural drawings if available (as-built drawings preferred); the proposed array size and roof coverage area; the proposed panel and racking system specifications including panel dead load (typically stated as kg/m² or kN/m²), racking dead load, and fixing type; and any recent roof condition survey or maintenance reports that contain relevant structural observations.

If structural drawings are not available, provide: the construction date or estimated date range; the building use class; internal photographs of the roof structure showing the purlin profile markings, member spacing, and any visible condition issues; and the postcode for site wind speed extraction.

For an on-site structural survey, the data package additionally includes the building owner's or facilities manager's contact details for access coordination, the site health and safety requirements (permit to work, induction requirements, PPE specification), and any drawings or records of previous structural works or modifications that are available.

Step 3, Specify the Output Format in Your Instruction

The most frequently overlooked element of commissioning a structural survey is the output format specification. Many project teams commission a structural survey with no format requirements stated, receive a report in the structural engineering firm's default format, and then discover that the format does not satisfy their MCS auditor, their lender's TA, or their G99 application requirements.

The solution is to specify output format requirements at the point of instruction. The specification should state: that the report must satisfy MCS MIS 3002 Section 5.9; that it must contain dead load and wind uplift calculations with Eurocode references; that the signing engineer must hold professional qualification or qualification (which must be stated on the report); and that the report must be suitable for G99 DNO submission and lender TA review. Firms experienced in commercial solar structural assessment will produce reports to this standard as a matter of course; firms without this background will benefit from the explicit specification.

Step 4, Submit the Instruction and Confirm Delivery Timing

Submit the instruction with the complete data package and receive written confirmation of the delivery timeline. For a desktop structural report with a complete data package for a standard commercial building, a 48-hour delivery benchmark from instruction confirmation is achievable. If the firm quotes a longer timeline, ask what the specific cause of the delay is, whether it is data gaps, engineer availability, or internal review processes. Data gaps can be addressed by improving the data package; the other factors are characteristics of the firm.

For an on-site structural survey, confirm the proposed site visit date, the engineer who will attend, and the report delivery timeline following the visit. On-site surveys typically require three to five days' lead time for scheduling, with the report delivered within 48 hours of the site visit.

Step 5, Review the Report on Receipt

When the structural report is received, conduct an initial review against the following checklist before incorporating it into the project file:

Step 6, File the Report and Maintain Traceability

File the structural report in the project documentation system with a clear reference to the specific building, the instructed assessment, and the date of the report. For portfolio programmes, maintain a master register of structural reports by site, including the report date, engineer name, verdict, and any conditions.

Retain the report throughout the project lifecycle. MCS audits, insurance renewals, and lender refinancing all require evidence of structural sign-off. A report filed at pre-construction that cannot be located at audit is operationally equivalent to a report that was never obtained. Document management is as important as the report itself.

Step 7, Communicate Conditions to the Installation Team

Where the structural report contains conditions on the clearance, and many reports do, those conditions must be communicated to the installation design team before the installation specification is finalised. This step is frequently skipped, particularly in large programmes where the structural report is filed by the project manager but not reviewed by the installation engineer.

A structural clearance that specifies a maximum panel weight of 15 kg/m² and is subsequently built with panels weighing 18 kg/m² is not a structural clearance for the system as built. The structural sign-off is only valid for the installation within the stated limits. Communicating conditions is not administrative housekeeping, it is the step that connects the engineering assessment to the built outcome.

The Data Pack: What to Prepare Before Instructing

The quality and completeness of the data submitted at instruction has a direct effect on the assessment turnaround time and the likelihood of a clean clearance result. Structural engineers working on desktop assessments can only assess what they can see in the submitted documentation. Gaps in the data pack do not prevent assessment, engineers work with available information and apply conservative assumptions where data is absent, but conservative assumptions inevitably produce more conservative results, which may mean a conditional clearance where an unconditional result would have been achievable with better data.

The essential data pack for a desktop structural assessment comprises: the full address and site postcode (for wind speed and snow load mapping); the building age (year of construction or approximate decade); the construction type (portal frame, post-and-beam, concrete frame, masonry load-bearing); the roof covering material (metal profile, fibre-cement, membrane, tiles); and the proposed PV specification including panel model, racking system, and proposed array layout if available. If existing structural drawings are held, either by the building owner, the local authority, or a previous structural engineer, they should be submitted as they reduce the need for conservative dimensional assumptions and may allow unconditional clearance where drawing-free assessment would return a conditional result.

For buildings where structural drawings are not available, dimensional data collected on-site provides the next best alternative. If someone on the project team can access the building, measurements of purlin section size and spacing, rafter span between portal legs, and roof pitch can replace the conservative assumptions that would otherwise be applied. Even a photograph of the purlin flange with a tape measure provides useful section depth data. This is not the same as a formal on-site structural survey but it gives the desktop assessor the specific data they need to perform an accurate calculation rather than a conservative assumption.

Reviewing and Actioning the Delivered Report

The structural report has been delivered. The file is a signed PDF. Now the project team needs to understand it and action any outstanding items before installation can proceed. This step is where the value of a well-structured report is realised, or where a poorly structured report generates unnecessary clarification requests and delays.

A well-structured commercial structural report contains the following in a predictable order: an executive summary with the clearance verdict stated unambiguously at the top; a description of the building and the information used as the basis of assessment; the methodology and standards applied; the calculation results for dead load, wind uplift, and snow loading; the clearance verdict with any conditions stated precisely; and appended calculations or wind zone diagrams where relevant. If the report begins with the clearance statement, “unconditional structural clearance is granted for the installation of the proposed PV array as described” or “structural clearance is granted subject to the following conditions”, the project team can immediately determine what action is required without reading the full technical content.

For conditional reports, the action required from the project team is to resolve each condition before installation proceeds. As discussed earlier, this typically means confirming that the racking system meets any stated dead load constraint and following any specified fixing enhancement at edge zones. The project manager should document the resolution of each condition in writing, a short email from the racking supplier confirming the system dead load, a note from the installer confirming enhanced fixing at edge zones, and file these alongside the structural report in the project record. This documentation package will be requested by MCS Scheme Providers, lenders, and insurers.

Managing Structural Sign-Off Across Multiple Procurement Routes

Commercial rooftop solar projects reach the structural assessment stage via different procurement routes, and the responsibilities and timescales differ accordingly. Understanding which procurement route applies to your project determines who instructs the structural engineer, who pays for the assessment, and how the report is managed through the project lifecycle.

Where the building owner is also the solar developer, a self-funder deploying solar on their own estate, the building owner typically instructs the structural engineer directly, and the report forms part of their own project documentation. This is the most straightforward procurement route: the client controls the instruction, receives the report, and determines when and how installation proceeds. The structural report remains their asset and does not need to be transferred to any third party unless a lender or insurer later requests it.

Where a third-party solar developer is deploying on a host building owner’s property under a roof lease or power purchase agreement, the question of who instructs and pays for structural assessment varies by deal structure. Some PPA and roof lease agreements place the structural assessment obligation on the developer. Others require the building owner to provide structural evidence as a condition of the lease agreement. Where the agreement is silent, it should be clarified before the project is substantially advanced, a dispute over who bears the cost of structural assessment can delay a project at an advanced stage if the allocation of responsibility is not agreed upfront.

EPC-contractor-managed procurement, where the developer contracts a design-and-build EPC to deliver the project to a defined specification, typically places structural survey responsibility within the EPC’s scope of work. In this route, the EPC instructs the structural engineer as part of their design obligations, and the structural report is delivered to the developer as part of the EPC’s project handover package. The developer should confirm this expectation is included in the EPC contract at appointment stage, not discovered at completion when the MCS documentation pack is assembled.

WHERE SOLAR SURVEYS ADDS VALUE