A solar mounting structure ends in the ground, and a lot of what can go wrong ends up there too. The same frame can sit on well-drained gravel in one corner of a site and on soft fill in another. Soil strength, groundwater and how the ground varies across the field all shape the foundation.

That is why choosing a foundation from the steel drawing alone is a guess. It needs ground data that describes the actual solar field.

What the ground investigation tells the designer

A geotechnical investigation provides what foundation design needs: soil layers, groundwater level, strength and, where relevant, settlement or lateral resistance. If the site includes fill, mixed soil layers or a patch of expansive or soft soil, one assumed bearing value cannot represent the whole project. The design basis should state what data was used and where it stops being reliable.

Coverage counts as much as content. The report should relate to this site, reach the depth the foundations need and be checked against the current layout.

  • Check where the boreholes or test pits sit relative to the array.
  • Read soil layers, groundwater and stated limitations together.
  • Compare the report date and layout with current project information.

Choosing something that can actually be built

Driven piles, screw piles, bored piles and concrete footings suit different ground and different loads. The structure delivers compression, uplift and sideways force, and the foundation has to resist all three. Access for equipment, tolerances, corrosion exposure, drainage and construction sequence often decide a close call, so they belong in the comparison alongside cost.

The aim is a safe, buildable solution backed by evidence, not the smallest foundation on paper. Where soil information is incomplete, options can be explored, but every assumption should be labelled and verified before the design is called final.

  • Match foundation actions to the structure's reactions.
  • Define installation checks and quality records, such as pile test results.
  • Note assumptions that wait on soil confirmation and re-check when data arrives.