What slope should the ground have around my house?

The International Building Code requires a minimum of 6 inches of fall in the first 10 feet from the foundation. In Oregon's wet climate, we recommend 1 inch per foot (8% slope) where possible. This ensures water moves away from the foundation even during heavy rainfall. The ground should slope away from the house in all directions.

How much does foundation regrading cost?

Regrading around a typical Oregon home costs $1,500-$5,000 for soil work alone. If drainage infrastructure (French drains, catch basins) is also needed, total costs range from $3,000-$12,000. The cost depends on how much area needs correction, soil conditions, and whether fill material must be imported.

How can I tell if my grading is wrong?

Signs include water pooling within 10 feet of the foundation, wet or damp basement or crawlspace walls, efflorescence (white mineral deposits) on concrete, standing water after rain that takes more than 24 hours to drain, and soil pulling away from the foundation. Any of these warrant a professional evaluation.

Can landscaping fix a grading problem?

Landscaping alone cannot fix a fundamental grading problem. Plants and mulch can help absorb some water, but if the ground slopes toward the foundation, no amount of vegetation will prevent water from reaching it. The grade itself must be corrected first, then landscaping can enhance drainage.

When is the best time to fix grading in Oregon?

The best time for grading work in Oregon is June through October when soils are dry and workable. However, if you are experiencing active water intrusion, temporary measures (extending downspouts, adding soil at the foundation) should be done immediately regardless of season, with permanent grading corrections scheduled for the dry season.

How Proper Grading Protects Your Home's Foundation

Why Grading Is Your Foundation's First Line of Defense

Your home's foundation is designed to support the weight of the entire structure for decades. But it was not designed to sit in water. When the ground around your home directs water toward the foundation instead of away from it, the results are predictable and expensive: cracks, settling, moisture intrusion, mold, and eventually structural failure.

In Oregon, where annual rainfall ranges from 35 inches in the Willamette Valley floor to 60+ inches in the foothills, proper grading is not a nice-to-have — it is essential. The difference between a dry crawlspace and a flooded one often comes down to a few inches of slope in the soil around the house.

Cojo Excavation & Asphalt performs residential grading throughout the I-5 corridor. Here is what every Oregon homeowner should know about how grading protects your foundation.

How Water Damages Foundations

Hydrostatic Pressure

When water saturates the soil around a foundation, it creates hydrostatic pressure — the force of water pushing against the foundation walls. Concrete is strong in compression but relatively weak in tension, and hydrostatic pressure creates tension on the inside face of the wall.

Over time, this pressure causes:

Horizontal cracks in poured concrete walls
Bowing or displacement of concrete block walls
Water seepage through cracks and joints
In extreme cases, wall failure

Erosion and Undermining

Water flowing along a foundation can erode the soil supporting the footing. Once soil is removed from under the footing, that section of foundation loses support and can settle, crack, or shift. This is especially common on sloped lots where concentrated water flow develops along one side of the house.

Freeze-Thaw Cycles

While Oregon's Willamette Valley rarely experiences deep freezes, areas at elevation (the Cascades foothills, the South Hills of Eugene, the West Hills of Portland) do see freezing temperatures. Water that saturates soil around a foundation expands when it freezes, pushing against the foundation walls and footings. Repeated freeze-thaw cycles accelerate cracking and displacement.

Soil Expansion and Contraction

Oregon's clay soils expand when wet and shrink when dry. This seasonal cycle creates alternating pressure against the foundation:

Wet season (October-May): Clay expands, pushing against walls
Dry season (June-September): Clay shrinks, pulling away and creating gaps that fill with debris
Next wet season: Clay expands again, but now must push against the debris, creating even more pressure

Over years, this cycle causes progressive cracking and displacement.

The Right Slope: What the Code Requires

Minimum Requirements

The International Residential Code (IRC Section R401.3) and Oregon Residential Specialty Code require:

Graded soil: Minimum 6 inches of fall within 10 feet of the foundation
Impervious surfaces (patios, sidewalks): Minimum 1/4 inch per foot slope away from the foundation
Swales within 10 feet: Must be graded to drain away from the foundation

These are minimums. In Oregon's climate, exceeding these minimums is wise.

What We Recommend for Oregon

Based on our experience with Oregon soils and rainfall, we recommend:

8 inches of fall in the first 10 feet (approximately 1 inch per foot or 8% slope)
Clay soil areas: 10 inches in the first 10 feet where possible, because clay absorbs water slowly and needs steeper grade to shed surface water effectively
Continuous slope: No dips, plateaus, or reverse grades within 15 feet of the foundation

Special Situations

Sloped lots: On downhill sides, water naturally flows away from the foundation. On the uphill side, water flows toward it. The uphill side needs aggressive grading plus a swale or French drain to intercept and redirect uphill water before it reaches the foundation.

Flat lots: On valley-floor lots with minimal natural slope, grading is even more critical because water has nowhere obvious to go. These lots often need a combination of grading and drain systems.

Adjacent structures: If a neighbor's garage, fence, or retaining wall is close to your foundation, grading options may be limited. Subsurface drainage (French drains) may be needed where surface grading alone cannot achieve adequate slope.

Signs Your Grading Is Failing

Exterior Signs

Water pooling near the foundation after rain — even small puddles within 3 feet of the house indicate a problem
Erosion channels along the foundation where water is flowing
Soil pulling away from the foundation — a gap between the soil and the concrete is a sign of clay shrinkage and poor drainage
Saturated soil that stays wet for days after rain while areas further from the house dry out
Downspout discharge pooling rather than flowing away from the house

Interior Signs

Damp or musty crawlspace — the single most common indicator of grading problems in Oregon homes
Water stains on basement walls or efflorescence (white mineral deposits) on concrete
Mold or mildew in lower levels of the home
Cracks in foundation walls — especially horizontal cracks, which indicate lateral pressure from water-saturated soil
Sticky doors and windows that change with seasons — this can indicate foundation movement from soil expansion/contraction cycles

When to Act

Do not wait for interior water damage to appear before addressing grading. By the time water is visible inside, the problem has been developing for months or years. Address exterior drainage issues as soon as you notice them.

How to Fix Grading Problems

DIY Fixes for Minor Issues

Add soil at the foundation: Purchase topsoil or fill dirt and build up the grade against the foundation, tapering outward to create the proper slope. Use soil that is at least 50% clay or silt (not pure sand or gravel, which allows water to drain straight down along the foundation). Do not pile soil above the siding line.

Extend downspouts: Add above-ground extensions or splash blocks to carry roof water at least 4-6 feet from the foundation. This is a quick fix that prevents concentrated water discharge at the foundation.

Regrade planting beds: If landscaping has created low spots near the foundation, reshape the beds to slope away from the house. Remove excess mulch that may be holding moisture against the foundation.

Professional Fixes

Full regrading: For widespread grading deficiencies, a contractor reshapes the grade around the entire home using a small excavator or skid steer. This typically involves importing fill material, establishing proper slopes, and restoring landscaping. Cost: $2,500-$6,000.

French drain installation: A perforated pipe in a gravel-filled trench intercepts groundwater before it reaches the foundation and routes it to a discharge point. This is the standard solution for persistent groundwater problems in Oregon's clay soils. Cost: $3,000-$8,000 for a residential system.

Curtain drain (uphill interceptor): On sloped lots, a curtain drain is installed across the uphill side of the house to intercept subsurface water flowing downhill. This prevents water from ever reaching the foundation area. Cost: $2,000-$5,000.

Complete drainage system: For severe or complex problems, a combination of regrading, French drains, downspout drains, catch basins, and a sump pump may be needed. Cost: $8,000-$20,000.

Grading and Your Driveway

Your driveway is one of the largest impervious surfaces near your home, and it directly affects foundation drainage:

Driveway slope should direct water away from the house or to a drain inlet
The joint between the driveway and the foundation must be sealed or graded so water cannot flow along the driveway surface into the foundation area
Cracked or settled driveways can redirect water toward the foundation

If your driveway is contributing to drainage problems, resurfacing or replacement may be the most effective long-term fix. Visit our residential paving page for options.

Prevention: Maintaining Proper Grading

Grading is not a set-it-and-forget-it solution. Maintain it with these annual checks:

Spring (March-April): After the wet season, walk the perimeter of your house and look for erosion, settlement, or new low spots. Fill any depressions with soil and restore slope.

Fall (September-October): Before the rainy season, verify that all grading is intact, downspouts are clear and extended, and drain outlets are not blocked by leaves or debris.

After landscaping changes: Any time you modify landscaping near the house — new beds, patios, walkways, fences — verify that drainage patterns are maintained.

After construction nearby: If neighbors build, roads are repaved, or utility work occurs near your property, check that the work has not redirected water toward your foundation.

Contact Cojo for a drainage evaluation if you are unsure about your grading.

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