Castle Pines Concrete Pools

Everyone talks about the shell. Tile, coping, plaster color, the shape of the sun ledge. Almost nobody asks the question that decides whether any of it lasts: what is this thing sitting in, and where does the water in that ground go?

A concrete pool is a huge rigid vessel buried in a hole cut into a hillside. On the wooded, sloped lots common through Lagae Ranch and up around The Village at Castle Pines, that hole is rarely uniform. One wall bears on undisturbed native material and the opposite wall bears on ground that was moved when the house pad was built. Add subsurface water tracking downhill and you have the two forces that break pool shells. So we start below the shell and work upward, with our in-house structural engineer involved from the first site visit rather than at the end as a signature.

The ground under the hole

Excavation tells us most of what we need. We look at what the bucket brings up wall by wall, because a pool that spans two different bearing conditions will crack along the line between them if nobody addresses it. Where the material is soft or was placed as fill, we over-excavate and rebuild with compacted structural fill until the bearing is consistent all the way around.

Deep end matters most. That's where the shell is thickest, the water column heaviest, and the load concentrated. It's also where the hole is most likely to reach into ground with different behavior than the shallow end. We shape the subgrade in steps and transitions rather than abrupt jumps, so the shell has no single line to hinge on.

Then the drainage. A hydrostatic relief valve in the floor is standard practice and cheap insurance. Beyond that, on a lot where water runs downhill toward the excavation, we install a gravel-wrapped subdrain around the shell and give it somewhere to go by gravity. Water that can't build pressure behind a wall can't push on it.

Below the waterline, before anyone shoots concrete

• Site walk with our structural engineer, including how the lot sheds water above the pool
• Excavation inspected wall by wall for bearing consistency, not just depth
• Soft or filled areas over-excavated and rebuilt with compacted structural fill
• Subgrade shaped in steps with smooth transitions instead of sharp changes
• Perimeter subdrain in washed rock with filter fabric, daylighted downhill
• Hydrostatic relief valve set in the deepest point of the floor
• Steel cage tied to the engineered drawing, held off the subgrade on supports
• All plumbing installed and held under pressure while concrete is placed

Shotcrete against a cast-in-place shell

Building a pool on the Front Range calendar

Excavation and shooting run from spring through fall, and the smart move is to break ground early in the season. A pool is not one pour; it's a sequence of trades, and every inspection and weather day stacks up. Start in May and you swim that summer. Start in July and you're plastering in October with your fingers crossed.

Cold weather doesn't end the work, it just narrows it. Shotcrete can be placed in the cold with heated material and protection, and the curing water has to be managed carefully so it doesn't freeze on the shell overnight. Frozen subgrade is where we stop, same as on any pour. Summer brings the opposite problem: hot dry air at this elevation pulls moisture out of fresh shotcrete fast, so we water cure it on a schedule for a week or two and we don't skip days.

Rain has one specific danger on a pool job. A soaking storm on an open excavation can slough a wall or soften the subgrade you just approved. We tarp, we cut diversion above the hole, and we'd rather lose a day than shoot against ground that turned to mud overnight.