Drainage problems in Denver usually come from soil that slopes toward the house, short downspouts and sprinklers spraying the foundation, all of which matter on expansive clay. Fixes include regrading, extending downspouts, moving spray heads and plants back from the house, swales, dry creek beds and French drains.
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Denver is dry, but drainage problems are still common here, and they can be costly. The reason is the soil. Parts of every major Front Range community sit on expansive clay that swells when it gets wet and shrinks as it dries, and that movement can crack foundations, slabs and walls. Summer thunderstorms and hail can also dump a lot of water in a short time, and spring snowmelt soaks soil that was already saturated.
Signs you have a drainage problem
- Soil next to the foundation that is level with or sloping toward the house
- Downspouts that empty right beside the foundation, or extensions that have been removed
- Sprinklers that spray the foundation wall
- Damp basement walls, cracks in window wells or a sump pump that runs after watering
- Gullies, exposed roots or rock washed onto walks on sloped lots
- Ice sheets on walks and driveways where meltwater collects in winter
Common solutions
- Regrading: rebuilding the soil around the house with compacted fill so it slopes away from the foundation.
- Downspout extensions and buried lines: moving roof water well away from the house. CSU Extension advises leaving downspout extensions in place on expansive soils.
- Moving plants and spray heads back: CSU Extension recommends keeping sprinkler spray out of the first five feet next to the house and planting trees at least 15 feet away.
- Swales: shallow channels that guide surface water around the house.
- Dry creek beds: rock-lined channels that carry storm water and look natural in a xeriscape.
- French drains: gravel and perforated pipe for areas that stay saturated, with a downhill outlet.
Erosion control on slopes
Foothill neighborhoods in Lakewood, Littleton and Castle Rock, and hillside lots in Parker and Arvada, can lose soil quickly when storms hit bare ground. Covering soil with plants, rock mulch or erosion-control blankets, terracing with walls, and slowing water with check structures all help. Fixing the source of concentrated water, such as a downspout or a neighbor's runoff, comes first.
Where the water goes
Water should be routed to a safe outlet on your property, a street or an approved drainage system, not concentrated onto a neighbor's lot. Some cities restrict discharging water across sidewalks, where it can freeze. Larger grading projects, or work near a creek, floodplain or drainageway, may need a permit, so check with your city or county.
Before you hire
- Watch where water goes during a storm, during snowmelt and while sprinklers run.
- Note where every downspout discharges.
- Ask the contractor where the water will end up and how the outlet will be protected.
- Contact Colorado 811 at least three business days before trenching, and mark private sprinkler lines yourself.
Water against a foundation in expansive soil is worth fixing sooner rather than later. Mark your request as urgent if it is actively getting in. Request a drainage company serving the Denver metro.
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Frequently asked questions
Why does drainage matter so much on Denver soils?
Expansive clay swells when wet and shrinks when dry. Repeated wetting next to a foundation can move slabs and walls, so keeping water away from the house is one of the most valuable things a landscape can do.
How far should plants and sprinklers be from my foundation?
CSU Extension recommends keeping most plantings and all sprinkler spray at least five feet from the house on expansive soils, unless plants need very little water, and planting trees at least 15 feet away.
Can I drain water onto my neighbor's yard?
Concentrating water onto a neighboring lot can cause disputes and liability. A good plan routes water to an appropriate outlet. Larger grading or work near a drainageway may need a permit, so check with your city.
Sources and further reading
- Colorado State University Extension
- CSU PlantTalk: Choosing a lawn grass for Colorado
- CSU PlantTalk: Expansive soils
- Denver Water: summer watering rules
- Denver Water: drought information
- Aurora Water: Grass Replacement Incentive Program
- City and County of Denver: fences and walls
- Denver Office of the City Forester: tree pests and diseases
- Colorado Department of Agriculture: pesticide applicator licensing
- Colorado Department of Agriculture: noxious weed species
- Colorado State Forest Service: Home Ignition Zone guide
- Colorado General Assembly: SB24-005 (nonfunctional turf)
- Colorado 811
- National Weather Service Boulder: Denver monthly climate normals
- USDA Plant Hardiness Zone Map
- EPA WaterSense