Two deliverables come up most often on commercial solar projects: a Desktop Structural Roof Loading Report, and a full on-site structural survey. They are not the same, and using the wrong one wastes either money or time.
The desktop roof loading report
A desktop assessment works from the information available: the proposed array, the mounting design, existing drawings and calculations where they exist, and the site data needed to derive wind and snow loads under the BS EN 1991 Eurocodes with the UK National Annexes. It produces a documented, signed position on whether the roof can carry the proposed system. It is the right starting point for most projects and the fastest route to compliant evidence.
The on-site structural survey
A physical survey is the right call when the desktop information is incomplete or cannot be relied on: a roof of uncertain construction, no reliable drawings, visible defects, or where a lender or insurer requires physical attendance. The surveyor verifies the structure as built, not as assumed, and documents its actual condition. For commercial, financed or uncertain roofs it is the thorough, lender-ready answer, and it is the product we recommend by default where there is any doubt.
| Question | Desktop report | On-site survey |
|---|---|---|
| Roof well documented? | Best fit | Not always needed |
| Old, undocumented or visible defects? | Limited | Best fit |
| Funder requires physical attendance? | No | Yes |
| Fastest route to compliant evidence? | Yes | Thorough, not fastest |
How to choose
If you have a clear array design and reasonable existing information, start with the desktop report. If the building is old, undocumented, or the funder demands physical sign-off, go straight to the on-site survey. When in doubt, the desktop stage often tells you whether a site visit is needed. Both are signed by a qualified structural engineer, both reference the BS EN 1991 Eurocodes with the UK National Annexes, and both are accepted by lenders, DNOs and Building Control.
Which is cheaper, a desktop report or an on-site survey?
The desktop report is the lower-cost, faster product. The on-site survey is the thorough option for uncertain or financed roofs, priced on application.
Will a desktop report satisfy MIS 3002 V6.0?
For a suitable, well-documented roof, yes, when it is signed by a qualified structural engineer against the standard.
Do I always need an on-site survey?
No. Many well-documented roofs are served by a desktop report. The survey is for uncertain, older or financed roofs.
Where Solar Surveys Helps
For uncertain, older or financed roofs, the on-site structural survey is the default, lender-ready route. For straightforward, documented roofs, the Desktop Structural Roof Loading Report is the fast, compliant option, and the roof survey hub compares the survey types in one place. To see what a desktop deliverable looks like, view the desktop report preview.
THE STRUCTURAL TRINITY
Three Reports That Clear a Commercial Solar Site for Installation
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