Site Grading & Drainage Inspection

Per NBC Section 9.14 and municipal bylaws, the finished grade around a building must slope away from the foundation at a minimum of 5% (1 in 20) for the first 1.5 m. The lot grading plan, typically required by the municipality, establishes design elevations for the building, property corners, swales, and drainage routes. All grading must conform to the approved lot grading certificate to prevent water ponding against foundations and to direct surface water to the municipal storm system or approved outlets.

1. Compare as-built grades at all property corners and building corners to the approved lot grading plan elevations

2. Verify the ground slopes away from the foundation at a minimum 5% gradient for the first 1.5 m per NBC Section 9.14.6.1

3. Confirm drainage swales are graded to the design profile with a minimum 2% longitudinal slope toward the outlet

4. Check that no grading directs surface water onto neighbouring properties without an easement or municipal approval

5. Verify that the overall site drainage pattern matches the approved lot grading certificate

- Finished grades not matching the approved lot grading plan elevations

- Insufficient slope away from foundation walls causing water ponding

- Drainage swales backfilled or obstructed after initial grading

- Surface water directed onto adjacent properties without approval

Per NBC Section 9.14.3, foundation drainage must be provided for all habitable buildings with basements or crawl spaces. Weeping tile (perforated drain pipe) must be installed at or below the level of the footing, surrounded by clear granular drainage material, and covered with filter fabric to prevent soil migration. The system must discharge to a sump pit with a pump, a gravity outlet, or the municipal storm system as permitted.

1. Verify weeping tile is installed at or below the bottom of the footing per NBC Section 9.14.3.1

2. Confirm perforated pipe is surrounded by minimum 150 mm of clear crushed stone wrapped in geotextile filter fabric

3. Check that the weeping tile has a minimum slope of 1% toward the discharge point or sump pit

4. Verify the sump pit and pump are installed per NBC Section 9.14.5 where gravity drainage is not available

5. Confirm the discharge point is connected to the municipal storm system or daylight outlet, not the sanitary sewer

- Weeping tile installed above the footing level providing inadequate drainage

- Filter fabric omitted allowing soil fines to clog the drainage stone and pipe

- Weeping tile connected to the sanitary sewer instead of the storm system

- Sump pump discharge too close to the foundation causing water recirculation

Per NBC Part 9 and CSA A23.1, backfill around foundations must be free of organic material, frozen soil, and debris. Backfill must be placed in lifts not exceeding 300 mm and compacted to a minimum 95% Standard Proctor density (ASTM D698) for areas supporting structures or pavements. Backfill must not be placed against foundation walls until the walls have achieved adequate strength and bracing is in place.

1. Verify backfill material is free of organics, frozen lumps, construction debris, and oversized stones

2. Confirm backfill is placed in maximum 300 mm lifts and compacted to 95% Standard Proctor density

3. Check compaction test reports (nuclear gauge or Clegg hammer) at the required frequency per specifications

4. Verify that foundation walls were adequately braced or the first floor installed before backfilling commenced

5. Confirm the final backfill elevation allows for topsoil placement while maintaining minimum grade requirements

- Backfill placed in lifts that are too thick resulting in inadequate compaction

- Organic material or construction debris mixed into backfill

- Backfill placed against green concrete or unbraced foundation walls

- Compaction testing not performed at the specified frequency

Per municipal stormwater management bylaws and provincial environmental regulations, developments must control the rate and quality of stormwater runoff. Post-development peak flows must typically not exceed pre-development levels for designated storm events. Low-impact development (LID) measures such as rain gardens, permeable pavement, and infiltration galleries may be required. Stormwater management reports must be approved by the municipality before construction.

1. Verify stormwater management facilities are constructed per the approved stormwater management report and drawings

2. Confirm detention or retention pond volumes, outlet structures, and overflow elevations match design specifications

3. Check that low-impact development features (rain gardens, permeable pavement, infiltration trenches) are installed per design

4. Verify roof downspouts discharge to splash pads or approved connections, not directly onto impervious surfaces draining to neighbours

5. Confirm erosion and sediment controls remain in place until vegetation is established per CSA W201

- Stormwater detention facility undersized or outlet control improperly installed

- Low-impact development features constructed with incorrect soil media or underdrains

- Downspouts discharging directly onto driveways or neighbouring properties

- Erosion and sediment controls removed prematurely before site stabilisation

Per municipal landscaping bylaws and lot grading requirements, a minimum depth of topsoil (typically 100-150 mm) must be placed over all landscaped areas. Topsoil must be free of weeds, debris, and contaminants. Seeded or sodded areas must achieve full coverage to prevent erosion. Tree and shrub planting must comply with municipal landscape plans, including species, size, and spacing requirements.

1. Verify topsoil depth meets the municipal minimum requirement (typically 100-150 mm) across all landscaped areas

2. Confirm topsoil quality is suitable for plant growth with no visible debris, stones larger than 50 mm, or weed infestation

3. Check that sod is laid tight to adjacent pieces with no gaps, staggered joints, and firm contact with the soil below

4. Verify tree and shrub species, calliper sizes, and planting locations match the approved landscape plan

5. Confirm that planted areas are mulched to the specified depth (typically 75-100 mm) around trees and shrub beds

- Topsoil depth insufficient due to over-grading or settlement of subgrade

- Poor topsoil quality with excessive clay content, debris, or weed seeds

- Sod laid over compacted or frozen subgrade preventing root establishment

- Trees planted too deep with the root flare buried below grade

Per municipal bylaws and NBC Part 9, driveways, walkways, and patios must be graded to direct surface water away from building foundations. Concrete flatwork must comply with CSA A23.1 for mix design and finishing. Interlocking pavers must be installed on a compacted granular base with edge restraints. All hardscape must meet accessibility requirements per NBC Section 3.8 where applicable.

1. Verify driveway and walkway grades slope away from the building at a minimum 2% and toward approved drainage outlets

2. Confirm concrete flatwork mix design meets CSA A23.1 exposure class requirements (typically C-2 for exterior slabs)

3. Check that interlocking pavers are laid on a properly compacted granular base with polymeric sand joints and secure edge restraints

4. Verify control joints in concrete are spaced per CSA A23.1 recommendations (typically 3 m maximum in each direction)

5. Confirm walkways comply with accessibility requirements where applicable, including maximum 5% running slope and 2% cross slope

- Hardscape graded toward the foundation instead of away from it

- Concrete flatwork without adequate control joints resulting in random cracking

- Interlocking pavers settling due to inadequate base compaction

- Missing edge restraints allowing paver creep and joint opening