Site Grading & Drainage Inspection

Per IRC R401.3, the ground must slope away from the foundation at a minimum of 6 inches within the first 10 feet. Per IBC Section 1804.4, final grading must direct surface water away from the building and toward approved drainage facilities. Finished grade must be at least 6 inches below the top of the foundation wall for frame construction and 4 inches for masonry per IRC R404.1.6. All fill material must be compacted to 95% of maximum dry density per ASTM D1557.

1. Measure the grade slope using a level and tape measure to verify minimum 6 inches of fall in 10 feet from the foundation

2. Verify finished grade is at least 6 inches below sill plate or top of foundation wall

3. Check that grading directs water away from the building on all sides

4. Confirm fill material is compacted per ASTM D1557 and compaction test reports are available

5. Inspect for areas of ponding or negative grade that direct water toward the structure

- Grade slopes toward the foundation instead of away, causing water intrusion

- Finished grade too close to the sill plate, allowing moisture and pest entry

- Fill material not properly compacted, leading to settlement over time

- Landscaping berms or beds creating reverse slope conditions against the foundation

Per IRC R401.3 and IBC Section 1804.3, surface water must be directed away from the building to an approved point of disposal. Swales and surface drainage channels must maintain positive slope of at least 1% (1/8 inch per foot) to convey water effectively. Downspout discharge must extend at least 6 feet from the foundation or connect to an underground drainage system. Impervious surfaces must be graded to prevent ponding.

1. Verify all downspout extensions discharge at least 6 feet from the foundation

2. Check swale grades for positive slope using a level to ensure water flows away from the structure

3. Run water through surface drainage paths to verify flow and identify any ponding areas

4. Confirm driveway and walkway grades slope away from the foundation

5. Inspect for erosion channels that indicate concentrated uncontrolled water flow

- Downspouts discharging directly at the foundation without extensions

- Swales with insufficient slope causing water to pond near the building

- Driveway or patio graded toward the foundation creating water intrusion

- Erosion channels forming from concentrated runoff at impervious surface edges

Per IRC R405.1, foundation drains are required around foundations enclosing habitable or usable spaces below grade. Drain tile or perforated pipe must be installed at or below the footing level, sloped at minimum 1/8 inch per foot, and surrounded by at least 6 inches of clean gravel covered with filter fabric per IRC R405.1. The drain must discharge by gravity or sump pump to daylight or an approved storm drainage system.

1. Verify foundation drain pipe is installed at or below the top of the footing per IRC R405.1

2. Confirm drain pipe is surrounded by clean gravel wrapped in filter fabric to prevent clogging

3. Check drain pipe slope at minimum 1/8 inch per foot toward the discharge point

4. Verify discharge point is at daylight or connected to an approved storm system

5. If sump pump is used, confirm it is operational with a check valve and discharges away from the foundation

- Foundation drain pipe installed above the footing level, failing to intercept groundwater

- Filter fabric missing, allowing soil fines to clog the drain pipe over time

- Drain pipe with insufficient slope or bellies that trap water

- Sump pump discharge directed back toward the foundation

Per EPA SWPPP requirements and local stormwater ordinances, construction sites must implement stormwater management controls to limit post-development runoff to pre-development rates. Detention and retention facilities must be sized per local engineering standards, typically for the 10-year or 25-year design storm. Per the Clean Water Act Section 402, sites disturbing one acre or more require an NPDES construction general permit and an approved SWPPP.

1. Verify the stormwater management plan is approved by the local jurisdiction

2. Inspect detention or retention basins for proper grading, outlet structures, and capacity

3. Confirm stormwater conveyance pipes and inlets are installed per approved plans

4. Check that post-construction stormwater BMPs (rain gardens, permeable pavers, etc.) are installed per design

5. Verify the NPDES permit notice of intent is filed and the SWPPP is available on site

- Detention basin not graded to design depth or outlet structure improperly installed

- Stormwater inlets clogged with construction debris

- Post-construction BMPs not installed or not matching the approved plan

- SWPPP not maintained or updated during construction phases

Per IBC Section 1807.3, retaining walls must be designed to resist lateral soil pressures including surcharge loads and hydrostatic pressure. Retaining walls exceeding 4 feet in height measured from the bottom of the footing to the top of the wall require engineering design per IBC Section 105.2. Drainage behind retaining walls is required per IBC Section 1807.3.2 to relieve hydrostatic pressure. Retaining walls must have adequate footings sized for the soil bearing capacity.

1. Verify retaining walls over 4 feet have engineered design drawings and permit approval

2. Inspect drainage behind the wall including gravel backfill and weep holes or drain pipe

3. Check wall alignment for plumb and any signs of leaning, bulging, or displacement

4. Verify footing depth and width match the engineered design

5. Confirm proper backfill material and compaction in lifts behind the wall

- Retaining walls over 4 feet constructed without engineering design or permits

- No drainage provided behind the wall, causing hydrostatic pressure buildup

- Wall leaning or bulging from inadequate design or improper backfill

- Footing undersized for the soil bearing capacity or not placed below frost line

Per EPA SWPPP requirements and NPDES construction general permit conditions, erosion and sediment controls must be installed before land disturbance begins and maintained throughout construction. Silt fencing must be installed per manufacturer specifications with the fabric buried at least 6 inches and posts spaced no more than 6 feet apart. Disturbed areas must be stabilized within 14 days of final grading per most NPDES permits. Inlet protection must be installed at all active storm drain inlets.

1. Verify silt fencing is properly installed with fabric trenched in and posts secure

2. Check that all active storm drain inlets have inlet protection devices installed

3. Confirm construction entrance has a stabilized pad to prevent sediment tracking onto roads

4. Inspect for areas of active erosion and verify corrective measures are in place

5. Verify disturbed areas are stabilized with seed, mulch, or erosion blankets within the required timeframe

- Silt fencing not trenched in, allowing sediment to flow underneath

- Storm drain inlet protection missing or overwhelmed with sediment

- Sediment tracked onto public roads from unstabilized construction entrance

- Disturbed areas left exposed beyond the permitted stabilization timeframe