Foundation Footings & Support Systems
NBC 9.15.3 Compliant Foundation Support Solutions
NBC 9.15.3 Foundation Footing Requirements
Footings provide a firm level base for walls, columns, and chimneys while spreading high loads to wider areas, reducing potential settlement. They must rest on undisturbed soil, rock, or compacted granular fill without pyritic material that could cause damage.
Critical Functions:
- 🏗️ Spread concentrated loads over wider area
- ⚖️ Reduce bearing pressure on soil
- 📐 Provide level base for construction
- 🛡️ Prevent differential settlement
NBC Compliance Areas:
NBC Table 9.15.3.4 - Minimum Footing Sizes
Strip Footings - Minimum Width (mm)
| Number of Floors | Exterior Walls | Interior Walls |
|---|---|---|
| 1 Storey | 250mm | 200mm |
| 2 Storeys | 350mm | 350mm |
| 3 Storeys | 450mm | 500mm |
Width Adjustments Required:
- • Add 65mm per storey of masonry veneer
- • Add 130mm per storey of masonry construction
- • Add 100mm per storey of interior masonry
- • Double width if water table < footing width
Column Footing Areas:
- • 1 Storey: 0.40 m² (640×640mm)
- • 2 Storeys: 0.75 m² (870×870mm)
- • 3 Storeys: 1.00 m² (1000×1000mm)
- • Based on 3m maximum spacing
Note: Sizes based on maximum 4.9m (16 ft) supported joist span and 2.4 kPa design load. Larger spans require proportional increases per NBC 9.15.3.3.
Critical Footing Requirements
Footing Thickness (NBC 9.15.3.8)
Thickness must provide flexural strength for cantilevered portions beyond walls.
Requirements:
- • Minimum 100mm (4") thickness
- • Thickness ≥ projection beyond wall
- • Unreinforced: T ≥ P (projection)
- • 45° shear line from wall face
- • Reinforcement allows reduced thickness
Example: 200mm wall on 600mm footing = 200mm projection = 200mm min thickness
Step Footings (NBC 9.15.3.9)
Required on sloping sites to maintain horizontal bearing and prevent sliding.
Specifications:
- • Maximum rise: 600mm (24")
- • Minimum run: 600mm (24")
- • Prevents shear failure in soil
- • Maintains horizontal top surface
- • Reduces excavation depth
Note: Steps higher than 600mm impractical due to soil instability
High Water Table Conditions
Water table near footings weakens soil bearing capacity in granular soils.
When Water Table < Footing Width:
- • Double footing width required
- • Applies to sand, gravel, silt
- • Not required for clay soils
- • Can raise footing with compacted fill
- • Consider dewatering during construction
Critical: 50% bearing capacity reduction with high water table
Footing Support (NBC 9.15.3.2)
Footings must rest on suitable material to prevent excessive settlement.
Acceptable Support:
- • Undisturbed natural soil
- • Sound bedrock
- • Compacted granular fill (95% SPD)
- • No organic material
- • No pyritic shale content
Testing: Soil bearing capacity per NBC Table 9.4.4.1
Our Foundation Footing Services
Strip Footings
- • NBC compliant sizing
- • Excavation to bearing soil
- • Form work & reinforcement
- • Concrete placement & finishing
- • Keyway for wall connection
$150-250 per linear meter
Column Pad Footings
- • Load calculations
- • NBC Table 9.15.3.4 sizing
- • Excavation & base prep
- • Reinforcement placement
- • Pedestal installation
$800-1,500 per pad
Step Footings
- • Slope site analysis
- • 600mm max rise/run
- • Stepped excavation
- • Reinforced connections
- • Level bearing surfaces
$200-350 per linear meter
Footing Underpinning
- • Deepen existing footings
- • Staged excavation
- • Temporary support
- • New concrete placement
- • Load transfer system
$500-800 per linear meter
Reinforced Footings
- • Engineering design
- • Rebar placement
- • Reduced thickness possible
- • Heavy load capacity
- • Special conditions
$250-400 per linear meter
Footing Repairs
- • Settlement correction
- • Crack injection
- • Undermining repairs
- • Drainage improvements
- • Stabilization work
$300-600 per linear meter
Footing Size Calculations
Spans Greater Than 4.9m (16 ft)
For joist spans exceeding 4.9m, footing sizes must be increased proportionally:
Calculation Method:
- 1. Sum supported joist lengths
- 2. Multiply storeys × 4.9m
- 3. Calculate ratio: Sum1/Sum2
- 4. Multiply table size by ratio
Example: 6m span, 2 storeys:
Ratio = 12m/9.8m = 1.22
350mm × 1.22 = 427mm required
Column Spacing Adjustments
NBC Table 9.15.3.4 assumes 3m maximum column spacing. Adjustments required:
Area Increase Formula:
If spacing > 3m:
New Area = Table Area × (Actual Spacing ÷ 3m)
Example: 4m spacing, 2 storeys:
0.75 m² × (4m/3m) = 1.0 m²
= 1000×1000mm pad required
Masonry Load Adjustments
Additional width required for masonry construction:
| Type | Add Per Storey |
|---|---|
| Brick Veneer | +65mm |
| Solid Masonry | +130mm |
| Interior Masonry | +100mm |
Pier Foundation Sizing
For manufactured homes and pier foundations:
Area Formula:
A = 1.5 × d ÷ p
- • A = footing area (m²)
- • d = pier spacing (m)
- • p = soil bearing (kPa)
Example: 3m spacing, 75 kPa soil:
A = 1.5 × 3 ÷ 75 = 0.06 m²
Professional Installation Process
Soil Investigation
Test soil bearing capacity per NBC Table 9.4.4.1. Check for water table, organic material, pyritic shale. Determine footing depth below frost line.
Load Calculations
Calculate building loads including dead, live, and snow loads. Determine required footing sizes per NBC 9.15.3.4. Account for masonry and special conditions.
Excavation
Excavate to required depth (min 1.2m frost protection). Ensure undisturbed soil at bearing level. Compact any fill to 95% SPD. Check elevations.
Form Work
Install forms to exact dimensions. Ensure level bearing surface. Add keyways for wall connection. Install reinforcement if required.
Concrete Placement
Place concrete meeting NBC 9.3.1 specifications. Vibrate for consolidation. Finish top surface level. Protect from freezing if required.
Curing & Protection
Maintain moisture for proper curing (7 days minimum). Strip forms after 24-48 hours. Install drainage before backfilling. Document for inspections.
NBC 9.15.6 Parging & Finishing Requirements
Parging and finishing are critical for moisture control through foundations. Concrete block walls require parging to provide an even, continuous base for dampproofing or waterproofing application.
9.15.6.1 Below Ground
Concrete Block Walls:
- ✓ Minimum 6mm (1/4") parging thickness
- ✓ Even and continuous coverage
- ✓ Coved over footing junction
- ✓ Substrate for dampproofing/waterproofing
Poured Concrete Walls:
- ✓ Form ties removed flush minimum
- ✓ Tie holes sealed with mortar
- ✓ Smooth surface for coatings
9.15.6.2 Above Ground
Masonry Walls:
- ✓ Tooled mortar joints preferred
- ✓ OR parging application
- ✓ OR other suitable finish
- ✓ Prevent rainwater leakage
Purpose:
- ✓ Resist rainwater entry
- ✓ Improve mortar-block contact
- ✓ Enhance appearance
9.15.6.3 Form Tie Requirements
Removal
- • Cut flush minimum
- • Both sides of wall
- • Below & above grade
- • Safety requirement
Sealing
- • Fill with mortar
- • Or dampproofing material
- • Smooth surface required
- • All holes & recesses
Purpose
- • Substrate preparation
- • Prevent water entry
- • Injury prevention
- • Coating adhesion
Parging Best Practices:
- • Apply in two coats for durability
- • First coat scratched for adhesion
- • Cure properly before waterproofing
- • Protect from freezing during cure
- • Use proper mix design (1:3 cement:sand typical)
NBC Concrete Requirements for Footings
📋 NBC 9.3.1 Concrete Specifications
Compressive Strength Requirements
| Application | Min. Strength |
|---|---|
| Walls, Columns, Footings | 15 MPa |
| Interior Floors | 20 MPa |
| Garage/Carport Floors | 32 MPa |
| Exterior Steps | 32 MPa |
Water/Cement Ratios
| Application | Max W/C |
|---|---|
| Walls, Columns, Footings | 0.70 |
| Interior Floors | 0.65 |
| Garage/Carport Floors | 0.45 |
| Exterior Steps | 0.45 |
❄️ Cold Weather Requirements (Air Temp < 5°C)
- • Concrete temp: 10-25°C during mixing
- • Maintain ≥10°C for 72 hours after placing
- • No frozen materials in mix
- • Protected curing required
- • Garage floors: 5-8% air entrainment
- • Exterior steps: 5-8% air entrainment
Aggregate Specs
- • Max: 1/5 form width
- • Max: 1/3 slab thickness
- • Well-graded, no organics
Curing Standards
- • 7 days minimum moist cure
- • 28-day strength testing
- • No load before full cure
Quality Control
- • Slump testing on-site
- • CSA A23.1 compliance
- • No site water addition
Site-Batched Concrete Mix (NBC Table 9.3.1.7): Standard mix ratio 1:2:3 (cement:sand:gravel) with controlled water content. Ready-mix concrete must meet CSA A23.1 standards for materials and methods.
Reference: National Building Code of Canada 2015, Part 9, Section 9.3.1 - Concrete
All concrete work meets or exceeds NBC requirements for structural integrity and durability.
Common Footing Problems & Solutions
Undersized Footings
Excessive settlement and cracking
Solution: Underpinning or footing enlargement
Frost Damage
Heaving and movement from freezing
Solution: Extend below frost line (1.2m min)
Water Table Issues
Reduced bearing capacity
Solution: Double footing width or dewater
Differential Settlement
Uneven support causing cracks
Solution: Soil stabilization or piers
Inadequate Thickness
Shear failure at projections
Solution: Reinforce or increase thickness
Poor Soil Conditions
Organic material or fill settling
Solution: Remove and replace with engineered fill
Foundation Footing FAQs
Why must footing thickness equal or exceed projection?
Unreinforced concrete tends to fail along 45° shear lines from the wall face. The thickness must equal projection to keep loads within this shear cone, preventing failure.
When are step footings required?
On sloping sites to maintain horizontal bearing surfaces and prevent sliding. Maximum 600mm rise and minimum 600mm run prevents soil instability and shear failure.
How deep should footings be in Toronto?
Minimum 1.2m (4 feet) below grade for frost protection in Toronto area. Greater depths may be required based on local conditions or building officials.
Can I use existing footings for an addition?
Existing footings must be verified for size, depth, and condition. Often require underpinning or enlargement to meet current NBC requirements for increased loads.
What soil bearing capacity is assumed in NBC tables?
NBC Table 9.15.3.4 assumes minimum 75 kPa bearing capacity. Lower capacity soils require proportionally larger footings. Site-specific testing recommended.
Do footings require reinforcement?
Not typically for residential footings meeting NBC 9.15.3 requirements. Reinforcement allows reduced thickness or handles special conditions like poor soils.
Ready to Protect Your Home?
Get a free inspection and quote from Toronto's most trusted waterproofing experts.