SOLAR STRUCTURAL ENGINEERING
What solar structural engineering actually answers
One question, asked of four different structures: can this carry a solar array safely for its design life, and if it cannot, what has to change. The array is comparatively light. What makes the question non-trivial is that it changes the wind regime across a surface, adds permanent load to a structure designed before anyone contemplated it, and does so for twenty-five years.
The standards do not change between a warehouse roof and a field of tables. What changes is which action governs and where the capacity has to be found. Naming that governing case, rather than assuming it, is the work.
THE SCOPE
Four structures, one standard of evidence
Rooftop assessment is our core work and the majority of what we issue. The rest of the scope exists because estates are rarely all one type, and because the standard should not drop when a site turns out to be a car park rather than a roof.
Rooftop Structural Surveys
The largest part of what we do. On-site assessment of an existing commercial roof against the array proposed for it, with the governing combination named under BS EN 1990 and a conclusion signed by a qualified structural engineer. Where a portfolio needs screening before survey, desktop structural roof loading reports cover the same question remotely at scale.
VIEW ROOFTOP STRUCTURAL SURVEYS →Ground-Mount and Solar Farms
A tilted plane in open terrain with nothing to shelter it. Wind governs, and the answer sits in the foundation rather than the frame.
VIEW →Solar Carports and Canopies
A new structure over occupied ground, carrying people and vehicles beneath it. Designed as a canopy first and an array second.
VIEW →Foundations and Substructure
Where every load path ends. Piles, screws, pads and ballast, plus the bases for inverters, transformers and battery storage.
VIEW →01 · THE COMMON STANDARD
The same basis, whatever the structure
Actions are derived under the BS EN 1991 series with the UK National Annexes: wind to BS EN 1991-1-4, snow to BS EN 1991-1-3, and permanent and imposed actions to BS EN 1991-1-1. They are then combined under BS EN 1990, which is where the governing case is established rather than guessed at.
This matters more than it sounds. A great many solar structural documents state a load and stop. A combination under BS EN 1990 states which case governs, which is the only form of the answer a funder, an insurer or a certification body can actually rely on.
One version note worth stating plainly: BS 6399-2 was withdrawn in 2010 and superseded by BS EN 1991-1-4. It still appears in circulation, including in automatically generated structural output. It is not a valid basis for a current assessment.
02 · WHERE SCHEMES GO WRONG
The failures are predictable
Terrain and altitude taken from a postcode rather than from the site. Wind and snow are both sensitive to where the structure actually stands, and a regional default is an assumption wearing the appearance of a derivation.
A single condition applied across a whole array. Perimeter zones, leading rows and corners carry substantially more uplift than the middle of a field or the centre of a roof. Uniform treatment is conservative where it does not matter and thin where it does.
The load path stopping at the frame. Uplift travels into connections, into the supporting structure and into the ground. An assessment that verifies the mounting system and says nothing about what it is fixed to has answered a smaller question than the one that was asked.
The foundation left until last. On ground-mount and carport schemes it is usually the element that decides feasibility and cost, and it is usually the element priced before anyone has looked at the ground.
03 · HOW A COMMISSION RUNS
From instruction to signed conclusion
Scope is agreed against the asset and the proposed array, and a quotation is issued to a 24-hour target. Where the scheme needs ground investigation, additional survey or access equipment, that is stated at quotation rather than discovered midway through.
Site work, where the scope includes it, is carried out by a qualified structural engineer rather than a general surveyor, with on-site mobilisation targeted at 24 hours. Roof condition assessment can be combined into the same instruction where the fabric is in question as well as the structure.
Reports are issued to a 48-hour target from confirmed scope. Every report carries calculations, a named governing combination and a stated conclusion, reviewed and signed by a qualified structural engineer, and is written to be relied upon by a third party rather than only by the party who commissioned it. Cover of £5m professional indemnity is in force.
04 · WHAT WE PROVIDE
Deliverables
- Structural assessment of the existing or proposed structure against the governing combination
- Wind and snow actions derived for the specific site under the BS EN 1991 series and the UK National Annexes
- Combination and named governing case under BS EN 1990
- Connection and load path verification through to the supporting structure
- Foundation and substructure verification to BS EN 1997 where the load path terminates in the ground
- Remedial or strengthening recommendation where capacity is not demonstrated
- Calculations and a stated conclusion, reviewed and signed by a qualified structural engineer
- Documentation in a format accepted by lenders, insurers, DNOs and certification bodies
FREQUENTLY ASKED
Solar structural engineering questions
What does solar structural engineering cover?
It covers whether a structure can carry a solar array safely for its design life, and what has to change if it cannot. In practice that means four related problems: rooftop arrays on existing buildings, ground-mounted arrays in open terrain, car park canopies, and the foundations and substructures that all of them stand on. The standards are the same across all four. What changes is which action governs and where the capacity has to be found.
Which standards are solar structural assessments carried out to?
Actions are derived under the BS EN 1991 series with the UK National Annexes, principally BS EN 1991-1-4 for wind and BS EN 1991-1-3 for snow, and combined under BS EN 1990 so the governing case is named. Geotechnical design follows BS EN 1997. BS 6399-2 was withdrawn in 2010 and is not a valid basis for a current assessment. For schemes within its scope, MCS MIS 3002 V6.0 sets the certification requirements.
Do I need a structural engineer for a rooftop solar installation?
It is our standard that every roof taking an array is assessed and signed by a qualified structural engineer. An existing roof was designed for the loads anticipated when it was built, and an array adds permanent load while changing the wind regime across the surface. Whether a given scheme is obliged to obtain that sign-off depends on the certification route it is following, but the structural question exists either way.
Can one firm cover rooftop, ground-mount and carport work on the same portfolio?
Yes, and there is a practical reason to prefer it. Estates are rarely all one type. Where the same engineers hold the assumptions across a portfolio, the standard of evidence does not change depending on which asset a given site turns out to be, and a funder or insurer reviewing the portfolio sees one methodology rather than several.
How quickly are structural assessments issued?
Quotations are issued to a 24-hour target and reports to a 48-hour target from confirmed scope. On-site mobilisation is targeted at 24 hours. These are working targets rather than contractual commitments, and where a scheme needs ground investigation or additional survey the programme is stated at quotation rather than discovered later.
EVIDENCE
The methodology is published
We publish the standards we work to, the specification an assessment is written against, and research drawn from our own survey record. A buyer should be able to check the method before commissioning rather than after receiving the report.
Assessment Specification Standards Library Published Research
One Standard.
Every Asset.
Rooftop, ground-mount, carport and foundation structural engineering for solar PV across the UK, signed by a qualified structural engineer.