A paver field that looked perfect in September and is rolling like water by April did not fail because of the pavers. It failed underneath.
The mechanism
Down the hill, a compacted aggregate base four inches deep under a pedestrian patio is a reasonable spec. The ground barely freezes, so the base does not move.
At 6,750 feet the ground freezes and thaws dozens of times a season. Any moisture trapped in or under the base expands when it freezes and lifts everything above it, then drops it back when it thaws. Do that forty times and a field that was laid dead flat is no longer flat, and the joints open up enough to start losing sand.
Two things drive it:
- Base depth and compaction. Shallow base has less structure to distribute the movement, and base placed in one thick lift never compacts properly through its full depth no matter how long the plate is run over it.
- Water with nowhere to go. Compacted base over native soil that does not drain becomes a bathtub. Snowmelt in March is a far bigger water event than any rainstorm here.
What a mountain install needs
- Excavation deeper than valley spec — the exact number depends on soil, exposure and whether you drive on it, which is why we dig a test hole before quoting rather than after.
- Aggregate placed and compacted in lifts, not one pour.
- A drainage path. Either the native soil percolates and you confirm it, or you build an outlet and daylight it somewhere useful.
- Edge restraint that will survive a plow blade or a blower, staked properly.
- Polymeric joint sand, and a plan for topping it up at year three.
The cost consequence
This is the honest reason a mountain paver quote comes in higher than the one from the company driving up from San Bernardino. More excavation, more aggregate, more haul, more compaction time. The gap is usually a few dollars a square foot. Redoing the patio is the whole number again plus demolition.
If a quote you are holding is significantly below the range we publish on our pavers and patios page, ask what base depth it assumes and whether there is a drainage outlet in the scope. Those two lines explain nearly every difference.