Rock sinking is one of the most frustrating landscape maintenance issues in our region—but the good news is that it’s preventable once you understand what’s happening beneath the surface.
This guide explains why rock sinking happens in Denver landscapes and provides 10 proven strategies to keep your rocks stable, level, and looking great for years.
Whether you’re repairing an existing rock bed or installing new landscaping, these techniques will save you time, money, and the ongoing frustration of constantly re-spreading stones.
What is rock sinking?
“Rock sinking” refers to the gradual process in which landscape rocks settle deeper into the soil over time, leaving your once-level rock bed uneven, patchy, or partially buried.
This isn’t just a cosmetic problem—it’s a structural and maintenance issue that affects how your entire landscape performs.
Why do landscape rocks sink into the ground?
Denver’s unique climate and soil conditions create a perfect storm for rock sinking. Several factors work together to draw your decorative stones downward.
Soil compaction and erosion
Denver’s clay-heavy soil is the biggest culprit. When clay gets wet from rain or irrigation, it expands. As it dries, it contracts and compacts. This repeated cycle creates voids and channels that allow rocks to slowly settle deeper.
Over multiple seasons, even large stones can drop several inches into the ground.
Freeze–thaw cycles
Colorado’s dramatic temperature swings amplify the problem.
When moisture in the soil freezes at night, it expands and pushes soil upward—this is called frost heave. During warmer daytime hours, the ice melts and the soil settles again, but never back to its original position. Small gaps and pockets form beneath your rocks, causing uneven surfaces by spring.
Lack of a proper base layer
One of the most common installation mistakes is placing decorative rock directly on soil. Without a stable, well-draining base layer, rocks push down into compactable soil under their own weight.
This is especially true for smaller stones like pea gravel, which create concentrated pressure points.
Heavy watering or poor drainage
When soil becomes saturated—during snowmelt, monsoon storms, or in poorly graded yards—it loses stability. Saturated clay can behave almost like mud, allowing rocks to sink deeper with very little resistance.
Lightweight or rounded rock types
Some rocks naturally sink faster:
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Rounded river rock and pea gravel don’t interlock, so they roll and shift.
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Lightweight volcanic rock and pumice lack the mass to resist soil movement.
Angular, heavier stones perform far better in Denver’s conditions.
10 tips to keep rocks from sinking
1. Remove and clean existing rocks
If you’re repairing a sunken rock bed:
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Remove all decorative rock with a flat shovel or rake.
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Sift rocks using hardware cloth or mesh to separate out soil and decomposed organic matter.
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Rinse the stones if necessary.
Cleaning is crucial—trapped dirt adds weight and accelerates sinking.
2. Compact the soil properly
Use a hand tamper for small areas or a plate compactor for large ones. Overlap each pass to eliminate air pockets and create a dense, stable base.
3. Add a crushed gravel or decomposed granite base layer
A proper foundation is essential.
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Install 2–3 inches of ¾-inch minus crushed gravel.
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Add 1–2 inches of decomposed granite (DG) on top.
These angular materials lock together when compacted, providing excellent drainage and stability.
4. Install high-quality landscape fabric
Use professional-grade geotextile fabric. It allows water to pass through while preventing soil from migrating upward into the rock layer—a major cause of sinking over time.
5. Choose stable, angular rocks
Angular stones such as crushed granite or crushed limestone interlock naturally and resist shifting.
For most landscapes, 1–2 inch rocks provide the ideal balance of aesthetics and stability. Larger rocks (3–4 inches) work well in high-traffic areas.
6. Ensure proper drainage and grading
Grade your landscape with at least a 2% slope away from structures. For problem areas, consider adding:
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A French drain
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A dry creek bed (functional and decorative)
Good drainage dramatically reduces sinking.
7. Use solid edging
Install durable edging—steel, stone, or heavy-duty composite—to keep rock and base layers contained. The edging should sit about 2 inches below the finished rock surface for an invisible yet effective barrier.
8. Maintain proper depth and distribution
Aim for:
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2–3 inches of rock depth for most areas
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4 inches for high-traffic zones
Spread rocks evenly to avoid heavy pressure points.
9. Maintain seasonally
In spring and fall:
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Inspect rock beds for sunken areas or exposed fabric.
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Remove leaves and debris to prevent decomposition under snow.
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Rake rocks smooth to prevent uneven melting and ice buildup.
Small issues are easier to correct early.
10. Combine mulch and rock strategically
Use both materials where they perform best:
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Mulch around plants to retain moisture and improve soil.
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Rock in open areas, paths, and low-maintenance spaces.
This combination reduces heat stress on plants and improves landscape longevity.
When to call a professional
If sinking continues despite proper installation, underlying soil or drainage issues may be at play. A qualified landscaper can diagnose:
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Soil composition
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Drainage patterns
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Grading issues
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Sun exposure
Mile High Lifescape specializes in Colorado landscapes and designs rock installations that stay attractive and low-maintenance for years.
Conclusion
Preventing rock sinking comes down to three fundamentals:
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Proper layering
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Effective water management
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Consistent maintenance
By installing a compacted base, using quality fabric, selecting the right rock, and managing drainage effectively, you can create rock landscapes that stay stable despite Denver’s clay soils, freeze–thaw cycles, and variable weather.
These proven techniques turn rock beds from ongoing maintenance headaches into long-lasting, water-wise features that fit both the climate and your lifestyle.
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