Basement Underpinning Calgary

Gain 2+ Feet of Ceiling Height

Many Calgary homes. Particularly bungalows and bi-levels built before 1990. Have basements with 6-foot ceilings or less. That’s below the 6’5” minimum finished ceiling height required by the Alberta Building Code for a legal secondary suite, and it’s not comfortable for any use.

Basement underpinning (also called bench footing or floor lowering) is the structural solution: we excavate and lower the basement floor to create the ceiling height you need.

OAF Construction performs basement underpinning as part of our full-service basement development offering. We handle the structural engineering, City of Calgary permits, excavation, waterproofing, and finishing. So the underpinning project flows directly into your basement development or legal suite build.

Who Needs Basement Underpinning?

• Legal suite development. Alberta Building Code requires a minimum 1.95 m (6’5”) finished ceiling height for a legal secondary suite
• Livable finished space. Most adults find anything under 7 feet uncomfortable for regular use. Underpinning to 8’ creates a basement that feels like an actual floor of your home
• Home theatre or gym. Acoustic insulation, dropped ceiling soffits, and proper lighting all reduce finished height
• Older Calgary bungalows. Homes in Hillhurst, Killarney, Forest Lawn, Ogden, and other pre-1980 inner-city neighbourhoods frequently have 5’8” to 6’2” basement rough heights

Benefits

• Enables legal suite development and the rental income and SSIP grant that come with it
• Increases livable square footage in a meaningful way
• Adds measurable value to the property
• Often the most cost-effective path compared to building an addition above grade
• Waterproofing is done as part of the process

OAF Underpinning Process

1. Structural Assessment. A structural engineer assesses your existing foundation walls, footings, and soil conditions. Engineering typically costs $800 to $2,000.
2. Permit Application. OAF submits a Building Permit application to the City of Calgary with the structural engineer’s drawings and specifications.
3. Excavation. Working in staged sections to maintain structural integrity, we excavate below the current floor slab.
4. New Footings and Foundation Work. New concrete footings and foundation extensions are poured at the lower level, tying into the existing structure.
5. Waterproofing. With the footing exposed, we apply interior waterproofing membrane or drainage board as appropriate.
6. New Floor Slab. A new concrete slab is poured at the lower elevation, with a vapour barrier underneath.
7. Basement Development. With the new height in place, OAF proceeds with full basement finishing or legal suite construction.

Costs in Calgary

• Partial underpinning (bench footing, one or two walls): $25,000 to $45,000
• Full perimeter underpinning: $60,000 to $130,000
• Engineering and permit fees: $1,500 to $4,000 additional

A Calgary basement suite generating $1,600/month in rent recovers $60,000 in underpinning costs in roughly 3 years.

Frequently Asked Questions

How long does basement underpinning take? Underpinning alone typically takes 6 to 10 weeks. Add 4 to 8 weeks for permit approval. Total project timeline for underpinning plus legal suite is typically 7 to 10 months.

What is the minimum ceiling height for a legal suite in Calgary? The Alberta Building Code requires a minimum finished ceiling height of 1.95 m (approximately 6’5”) in habitable rooms of a secondary suite.

Can I combine underpinning with the SSIP grant? Yes, if the underpinning is performed as part of a legal secondary suite development project and you’ve received SSIP pre-approval before construction starts.

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