GROUND-MOUNT STRUCTURAL ENGINEERING
What actually governs a ground-mount structure
A ground-mounted array is a tilted plane standing in the open. There is no building around it to shelter it, no parapet to break the flow, and no roof structure to share the load. The consequence is that the case which governs the design is almost always wind, and the element that decides whether the scheme works is almost always the foundation rather than the frame above it.
That is a different problem from a rooftop array, and it is answered with different work. What does not change is the standard of evidence: actions derived for the specific site, combined under BS EN 1990 so the governing case is named, and a conclusion signed by a qualified structural engineer.
01 · THE GOVERNING ACTION
Wind on a tilted plane, in open terrain
Wind actions are derived under BS EN 1991-1-4 and its UK National Annexe. For a ground-mount site that means an exposed terrain category, a site-specific basic wind velocity, and pressure coefficients appropriate to a free-standing inclined surface rather than to a roof.
The critical condition is usually uplift rather than downforce, and it usually acts hardest on the leading row and the outer edges of the array field, where the flow has not yet been disrupted by the tables in front. An assessment that treats every table as identical will understate what the perimeter has to resist.
Uplift does not stop at the frame. It travels into the posts and out into the ground, which is why the wind case and the foundation case cannot sensibly be looked at separately.
02 · SNOW
Snow does not lie evenly between rows
Snow actions come from BS EN 1991-1-3 and its UK National Annexe, with characteristic ground snow load derived from the site’s own altitude rather than from the nearest town or a postcode centroid. On a ground-mount site that distinction matters, because these schemes are frequently on higher and more exposed ground than the buildings nearby.
The distribution matters as much as the magnitude. Snow can slide down a tilted plane and bank against the lower edge, and it can accumulate in the gaps between table rows. The loaded case that governs is therefore rarely an even blanket across the site, and modelling it as one is optimistic in the wrong direction.
03 · FOUNDATIONS
The foundation is the design decision
Ground screws, driven piles, concrete pads and ballasted trays are all legitimate solutions. Which one is correct is decided by the ground and by the uplift the foundation has to resist — not by what is quickest to install or cheapest to buy.
Foundation and substructure design is long-standing core work for our engineers, across commercial and industrial projects well beyond solar. The discipline transfers directly: a pile resisting uplift is a pile resisting uplift. What is specific to solar is the load case above it, and that is the part we derive from the array rather than assume.
Where a design depends on pull-out capacity, that capacity should be demonstrated on site rather than taken from a manufacturer’s table. Ground varies across a field, and a single figure applied to a whole site is an assumption wearing the clothes of a test result.
04 · MOVEMENT AND SETTLEMENT
Long rows move, and the ground under them is not uniform
A table row is a long, thin, exposed steel structure. It expands and contracts, and the detailing has to allow it to do so without locking in force or working the fixings loose over a twenty-five year life.
Beneath it, ground conditions change across a site. Differential settlement along a row shows up as misalignment, as strain in the frame, and eventually at the module clamps. Both are ordinary engineering problems, and both are considerably cheaper to resolve at design stage than after the tables are standing.
05 · WHAT WE PROVIDE
Deliverables
- Wind and snow actions derived for the specific site, with the governing combination named under BS EN 1990
- Table and frame assessment, including the perimeter and leading-row condition
- Foundation assessment and type selection against uplift, overturning and the available ground
- Substructure design for inverter stations, transformer plinths and battery storage bases
- Calculations and a stated conclusion, reviewed and signed by a qualified structural engineer
- Output written to be relied upon by a funder, an insurer or a certification body, not only by the party who commissioned it
Quotations to a 24-hour target, reports to a 48-hour target from confirmed scope. £5m professional indemnity cover in force.
FREQUENTLY ASKED
Ground-mount structural questions
What governs the structural design of a ground-mounted solar array?
In most cases wind rather than self weight. A ground-mounted array is a tilted plane in open terrain with no surrounding shelter, so uplift and overturning under wind actions to BS EN 1991-1-4 and its UK National Annexe usually govern the frame and, more importantly, the foundation. Self weight is comparatively small and rarely decides anything on its own.
Which foundation types are used for ground-mounted solar, and how is one chosen?
Ground screws, driven piles, concrete pads and ballasted trays are all used. The selection is driven by the ground conditions and by the uplift the foundation has to resist, not by preference. Where the design relies on pull-out capacity, that capacity should be demonstrated by on-site testing rather than assumed from a catalogue value.
Does snow matter on a ground-mounted array?
Yes, and not uniformly. Snow can accumulate in the gaps between table rows and against the lower edge of a tilted plane, so the loaded case is not the same as an even blanket across the site. Snow actions are derived under BS EN 1991-1-3 and its UK National Annexe, with site altitude taken from the location rather than the postcode.
Do you provide engineer-signed output for ground-mount schemes?
Yes. Every assessment we issue is reviewed and signed by a qualified structural engineer. That is our own standard and we apply it to ground-mount work exactly as we do to rooftop work.
THE WIDER STRUCTURAL SCOPE
One engineering team, either side of the roofline
Most estates are not exclusively rooftop or exclusively ground-mount, and the structural standard should not change depending on which a given site turns out to be. We cover both, alongside the canopy and foundation work that sits between them.
Rooftop Structural Surveys Roof Condition Assessments Published Research
Wind Case Derived.
Foundation Answered.
Ground-mount, carport and rooftop structural engineering for solar PV across the UK, signed by a qualified structural engineer.