Technical Guide: Screw Pile Foundation Details

Screw pile foundations are a modern, efficient alternative to traditional concrete footings, offering superior load capacity, faster installation, and long-term stability. This guide covers key technical details—from design considerations to installation best practices—for engineers, builders, and homeowners in Calgary.

1. Screw Pile Foundation/Design & Engineering Specifications

Key Components

• Helical Plates: Typically 8" to 16" diameter (varies by load)

• Shaft: Square or round steel (2⅞" to 4½" OD)

• Galvanization: Hot-dip zinc coating (minimum 3.9 mils) for corrosion resistance

Load Capacity Standards

• Residential: 10–50 kips/pile (varies with soil)

• Commercial: Up to 200+ kips/pile (engineered solutions)

• Testing: Each pile load-tested to 150% of design capacity

Soil Adaptability

Soil Type	Helix Configuration	Torque Requirements
Clay	Single/multi-helix	4,000–7,000 ft-lbs
Sand	Multi-helix	5,000–8,500 ft-lbs
Rock	Rock-socket helix	10,000+ ft-lbs

2. Installation Process: Step-by-Step

1. Site Assessment

• Soil testing (shear strength, moisture content)

• Frost depth verification (6–8 ft in Calgary)

2. Equipment Setup

• Hydraulic drive heads (5,000–30,000 ft-lbs torque)

• Laser-guided alignment systems (±1° tolerance)

3. Installation Metrics

• Speed: 15–30 minutes/pile (typical residential)

• Depth: Minimum 1 helix diameter below frost line

• Torque Monitoring: Real-time verification (1 kip = 10 ft-lbs torque)

3. Advantages Over Concrete Foundations

Feature	Screw Piles	Concrete
Installation Time	Hours	28-day cure
Load Ready	Immediately	28-day cure
Frost Heave Risk	None (below frost line)	High
Soil Disturbance	Minimal	Extensive
Lifespan	50–75 years	30–50 years

4. Calgary-Specific Considerations

• Permitting: Complies with Alberta Building Code (Section 9.15)

• Seismic Design: Lateral load resistance up to 0.3g PGA

• Winter Installation: No ground thawing required (operates to -30°C)

5. Frequently Asked Technical Questions

Q1: How are screw piles connected to structures?

A: Via bolted or welded pile caps, with options for:

• Wood posts (saddle brackets)

• Steel beams (moment connections)

• Concrete grade beams (rebar cages)

Q2: What’s the maximum lateral load capacity?

A: Up to 20% of vertical capacity (enhanced with grouted shafts or diagonal bracing).

Q3: How do you verify bearing capacity?

A: Through torque-to-capacity correlation (1 kip = 10 ft-lbs) + optional load tests.

Q4: Can piles be installed near utilities?

A: Yes—potholing verifies locations; mini rigs work in 6’ clearances.

Q5: What’s the maintenance requirement?

A: None for galvanized piles. Inspect brackets/bearings every 10 years.