Two gardens twenty minutes apart can need completely different footings, and nothing on the surface will tell you why. One sits on gravel that drains itself by lunchtime. The other sits on clay that holds water like a bowl and moves with the seasons. A spec written for one and used on the other doesn't just underperform. It fails on schedule. So before a design gets drawn or a material gets chosen, the first question on any Etonic job is one nobody sees in the finished photos: what's actually in the ground.
Gravel along the Hamble and the Solent
Warsash, Bursledon, Locks Heath and Sarisbury Green sit largely on the river terrace gravels that run down toward the Hamble and out to the Solent. It's honest ground to build on: free-draining, quick to dig, and forgiving of a sub-base that's compacted properly. The trap is assuming it behaves the same at every depth. Close to the water, particularly on the lower plots near Warsash, gravel can sit wet a foot or two down even when the surface looks bone dry. We've opened trial holes on jobs a few streets apart and found one dry at 300mm and the next holding standing water. That difference decides whether a soakaway is viable at all, and it's the kind of thing that has to be checked with a spade, not assumed from the postcode. It matters for a patio's drainage falls just as much as it matters for a lawn that's about to be turfed or a raised bed that needs to hold water rather than lose it.
The clay behind it
Move a little further from the water, into Fareham, Titchfield and parts of Whiteley, and the ground turns to the heavier Hampshire Basin clay. Clay drains slowly and moves with moisture: it swells when it's wet and shrinks hard in a dry spell. That movement is what cracks a poorly founded wall and lifts a patio that wasn't built deep enough underneath. It's why our sub-base on clay goes to 200mm rather than the 100 to 150mm we'd use on gravel, a point we've gone into properly in why mortar spec matters more than the slab on top. Clay changes the drainage plan too. It rarely percolates well enough for a simple soakaway, so a proper percolation test, correct falls, and a real outfall for the water matter here more than almost anywhere else we work.
Portsdown Hill, and the chalk that keeps its distance
Behind Portchester and the northern edge of Fareham, the ground climbs onto Portsdown Hill, a chalk ridge that's the nearest this part of Hampshire gets to true downland. Chalk digs easily and drains well, which sounds like good news until you hit one of the solution features chalk is prone to: a softer, water-filled pocket where the rock has slowly dissolved away underneath a perfectly solid-looking surface. It isn't common, but it's exactly the kind of thing you want to find with a trial hole before a patio's been set out, not after a corner's started to sink. Chalk also runs distinctly alkaline, which rules out the acid-loving planting that does well a few miles south on the gravel, and it's worth knowing before anything gets ordered from a nursery.
Made ground on the newer plots
New-build plots are their own category, and a growing share of the work here, as Warsash, Whiteley and the edges of Fareham keep developing. Ground that's been regraded, backfilled or built over during construction doesn't behave like undisturbed soil. It can hide rubble, compact unevenly, or simply not be what the site plan says it is underneath. On the new-build garden in Warsash we dug several trial holes across one plot and found three different conditions in three corners: clean gravel, a pocket of clay fill, and a strip of genuinely made ground over what had been a builder's access track. Nothing about the surface gave that away.
Why this comes before the spec, not after
None of this needs a geological survey. It needs someone to put a spade in the ground before writing a price. We dig down to sub-base depth in a couple of spots, note what's there in layers, and check whether water shows up and how fast it moves away again. That's the actual reason a written brief and price only goes out after we've walked the site, never before it. The sub-base depth, the drainage plan and sometimes the whole design depend on what's really there, and that's covered properly, not guessed at, in what we send you afterwards. We go into what that written brief and price actually contains in what's actually in a hard-landscaping quote. It's a slower way to quote than working off a photo and a plan. It's the only way we're comfortable putting our name to what goes in underneath.
The same trial hole tells us more than where to set the sub-base. It tells us what will actually establish. Free-draining gravel dries out fast in a Hampshire summer and needs planting that can take it. Heavy clay holds moisture and nutrients but sits wet around the roots all winter, and not everything copes with that. We plan the planting around the ground that's actually there rather than a generic list, which is one reason the schemes we build tend to still look considered five years on rather than half-replaced.
If you're planning a build anywhere between Southampton and Portsmouth, it's worth knowing what you're sitting on before you get a price for what goes on top. Send a brief through here and we'll come and dig a hole before we write anything down.