Foundations and Geotechnical Inspection

Per NBC 4.2.1 and NBC 9.15.2, foundations must be designed for the bearing capacity of the supporting soil. NBC Table 9.15.2.1 provides presumptive bearing capacities for common soil types. A geotechnical investigation per CAN/CSA-A434 is required where soil conditions are uncertain or for buildings exceeding Part 9 limits. The bearing surface must be undisturbed native soil or properly compacted engineered fill.

1. Verify the geotechnical report recommendations are reflected in the foundation design

2. Confirm the bearing surface matches the soil type assumed in the design — inspect excavation bottom

3. Check that the bearing stratum is at the depth identified in the geotechnical report

4. Verify no organic material, topsoil, or debris remains at the bearing surface

5. Confirm engineered fill, if used, is compacted to the specified density with test results documented

- Foundation placed on fill or organic soil instead of the required bearing stratum

- Bearing capacity overestimated without a proper geotechnical investigation

- Excavation overcut and backfilled without proper compaction

- Water table higher than anticipated reducing effective bearing capacity

Per NBC 9.15.3 and CSA A23.3, strip footings for residential construction must have minimum width and thickness as specified in NBC Table 9.15.3.4. Footings must extend minimum 1200 mm below grade (or to the frost depth for the region) per NBC 9.12.2.2. Reinforcement must be placed per structural drawings with proper cover — minimum 75 mm for concrete cast against soil per CSA A23.1.

1. Verify footing width and thickness meet NBC Table 9.15.3.4 minimums or structural drawing dimensions

2. Confirm footing depth is below the frost line — minimum 1200 mm or per local frost depth requirements

3. Check reinforcement placement, bar size, and spacing against structural drawings

4. Verify concrete cover — minimum 75 mm for surfaces cast against soil per CSA A23.1 Table 17

5. Confirm footing is level and in the correct location per the building layout

- Footing depth insufficient for local frost penetration depth

- Reinforcement placed without adequate cover on the soil side

- Footing width undersized for the soil bearing capacity

- Footing not level causing uneven wall loads

Per NBC 9.15.4 and CSA A23.3, cast-in-place concrete foundation walls must meet minimum thickness requirements — 150 mm for walls up to 2.4 m height per NBC Table 9.15.4.2. Walls must be reinforced per structural requirements to resist lateral earth pressure. Concrete must meet CSA A23.1 exposure class requirements — typically C-2 for below-grade exposure in most Canadian climates.

1. Verify wall thickness meets NBC Table 9.15.4.2 minimums or structural drawing dimensions

2. Confirm vertical and horizontal reinforcement is placed per structural drawings before pour

3. Check concrete exposure class on delivery tickets — C-2 minimum for below-grade per CSA A23.1

4. Verify wall height, plumb, and alignment — tolerance per CSA A23.1 Section 6

5. Confirm anchor bolts for sill plate are embedded at correct spacing and projection per NBC 9.23.6

- Foundation walls not plumb or aligned causing framing difficulties

- Concrete exposure class insufficient for below-grade durability

- Anchor bolt spacing or placement incorrect for sill plate attachment

- Honeycomb or cold joints from poor concrete placement

Per NBC 9.13.2, below-grade portions of foundation walls enclosing habitable space must be waterproofed or damp-proofed. NBC 9.14.2 requires a foundation drainage system (weeping tile) around all footings. Drainage tile must be minimum 100 mm diameter, sloped to a positive outlet, and surrounded by clear granular material. Waterproofing membranes must extend from the footing to above grade.

1. Verify waterproofing membrane is applied continuously from footing to minimum 150 mm above grade per NBC 9.13.2

2. Confirm weeping tile is installed around all footings at or below footing level per NBC 9.14.2

3. Check that drainage tile is minimum 100 mm diameter, sloped to a positive outlet (sump or daylight)

4. Verify clear granular material surrounds the drainage tile to a minimum 150 mm depth per NBC 9.14.3

5. Confirm protection board or drainage mat is installed over waterproofing membrane to prevent damage during backfill

- Waterproofing membrane damaged during backfill operations

- Weeping tile not sloped to a positive outlet causing water accumulation

- Insufficient granular material around weeping tile causing silting and blockage

- Waterproofing not extended high enough above anticipated grade level

Per NBC 9.14.6, backfill must not be placed until the foundation walls have adequate strength to resist lateral earth pressure — typically after first-floor framing provides bracing. Backfill material must be free of organic matter, frozen soil, and large rocks. Finished grade must slope away from the building at minimum 1:50 (2%) for the first 2 m per NBC 9.14.6.2 to direct surface water away from the foundation.

1. Confirm foundation walls are adequately braced before backfill — first-floor framing in place per NBC 9.15.4.7

2. Verify backfill material is free of organic matter, frozen soil, and rocks larger than 150 mm

3. Check that backfill is placed in lifts not exceeding 300 mm and compacted per specifications

4. Verify finished grade slopes away from the building at minimum 1:50 (2%) for the first 2 m per NBC 9.14.6.2

5. Confirm window wells are installed where required and drain to the foundation drainage system

- Backfill placed before first-floor framing causes lateral pressure damage to walls

- Frozen soil used as backfill settles excessively when thawed

- Finished grade slopes toward the building directing water to the foundation

- Excessive backfill height against unbraced foundation walls

Per NBC 9.12.2.2 and 9.15.2.1, foundations must extend below the depth of frost penetration or be protected against frost action. Frost depth varies across Canada from approximately 1.2 m to over 2.5 m depending on location. Frost-protected shallow foundations (FPSF) are permitted per CAN/CSA-S501 as an alternative. Slab-on-grade construction requires perimeter insulation per NBC 9.25 for thermal performance.

1. Verify foundation depth meets local frost penetration depth as specified in NBC climatic data tables

2. Confirm frost-protected shallow foundation insulation, if used, meets CAN/CSA-S501 requirements

3. Check that slab-on-grade perimeter insulation is installed per NBC 9.25 for the climate zone

4. Verify sub-slab insulation and vapour barrier (minimum 6 mil polyethylene) per NBC 9.25.3

5. Confirm that no frost-susceptible soils are left under shallow footings without adequate protection

- Foundation depth insufficient for local frost penetration causing frost heave

- Perimeter insulation missing or inadequate for the climate zone

- Sub-slab vapour barrier torn or missing leading to moisture problems

- Frost-protected shallow foundation insulation not extended far enough from the building

Per NBC 9.13.4, all new buildings with a slab-on-ground must include a soil gas barrier and a rough-in for a sub-slab depressurization system. The rough-in includes a sealed granular layer beneath the slab, a gas-permeable membrane, and a capped pipe extending from beneath the slab through the building envelope. This allows future activation if radon testing indicates levels above the Health Canada guideline of 200 Bq/m3.

1. Verify granular layer beneath the slab is minimum 100 mm of clean gravel per NBC 9.13.4

2. Confirm gas-permeable membrane is installed and sealed at all edges and penetrations

3. Check that the radon rough-in pipe (minimum 75 mm diameter) extends from below the slab to above the roof line or is capped for future extension

4. Verify all slab penetrations (plumbing, electrical) are sealed to prevent soil gas entry

5. Confirm the system can be easily activated with a fan if radon levels exceed 200 Bq/m3

- Radon rough-in pipe omitted during construction

- Granular layer too thin or uses inappropriate material reducing gas permeability

- Slab penetrations not sealed allowing soil gas bypass

- Rough-in pipe terminated in an inaccessible location preventing future activation