Basement underpinning increases your basement ceiling height by lowering the floor - the key that unlocks a legal basement apartment in an older Ontario home. Ontario Design Studio prepares BCIN-certified permit drawings coordinated with P.Eng structural design for underpinning projects across Ontario, so your foundation work is engineered, sequenced, and permit-ready.
When Is Underpinning Required?
The Ontario Building Code requires a minimum ceiling height of 1.95 m (6′5″) in the habitable rooms of a legal dwelling unit. Many older Ontario homes have basement ceilings of only 6′0″ to 6′2″ - so 3 to 5 inches of additional depth is needed before a basement apartment can be approved. Underpinning (or bench footing) is how you gain that height without moving the house.
Need to raise your basement ceiling height?
Ontario Design Studio delivers BCIN-certified drawings with coordinated P.Eng structural design across Ontario and the GTA. Call 416-558-9607 or request your free quote.
Underpinning vs. Bench Footing
There are two ways to gain basement height, and the right one depends on your budget, water table, and how much floor area you can give up:
- Underpinning extends the existing foundation deeper by excavating and pouring new footings below it, section by section. It gives you the full floor area at the new lower level and the most usable ceiling height - the premium option for a legal apartment.
- Bench footing builds an angled concrete "bench" along the inside of the foundation instead of going below it. It is faster and less expensive, but you lose a strip of floor area around the perimeter. It suits tighter budgets or high-water-table lots where deep excavation is risky.
We assess your foundation, soil, and goals and recommend the approach that gives you the most usable space for the money.
Why Underpinning Requires a Structural Engineer
Underpinning temporarily removes support from beneath a loaded foundation, so it is always engineered work. A Professional Engineer (P.Eng) designs the footing dimensions, reinforcement, and the strict excavation sequence - typically working in small alternating "pins" so the house is never unsupported. Ontario Design Studio prepares the architectural permit drawings and coordinates the structural engineering under one package, so your submission is complete and consistent.
Our Drawing Package
- Foundation plan showing the underpinning sequence and pin layout
- Structural details coordinated with P.Eng - footing dimensions, reinforcement, and sequence plan
- Cross-section showing existing and proposed floor levels
- Waterproofing and drainage details for the new deeper foundation
- Grading plan where exterior grade changes are required
The Underpinning Process
- Design & permit - we prepare the drawings and P.Eng structural design and obtain the building permit
- Sequenced excavation - the foundation is underpinned in small alternating sections so the house stays supported
- New footings poured - each pin is excavated, formed, and poured to the engineered depth, then cured
- Slab, waterproofing & inspections - the new lower slab and drainage are completed with City inspections at each stage
Underpinning Costs
Underpinning is a significant structural project, and drawing plus engineering fees reflect that. Our 2026 building permit cost guide breaks down BCIN and structural fees; construction cost is separate and depends on the depth, perimeter, and access. Contact us for a free quote on the design package.
Cities We Serve
We prepare underpinning permit and structural drawings across the GTA and Ontario, including Toronto, Mississauga, Brampton, Vaughan, and Markham. View all service areas →
Related Services
- Legal Basement Apartment Permits
- Basement Separate Entrance Permits
- Structural Engineering Drawings
- Building Permit Drawing Cost Guide
Frequently Asked Questions
What is basement underpinning?
Basement underpinning is a construction process that increases your basement ceiling height by lowering the floor level. It involves excavating beneath your existing foundation in controlled sections and pouring new concrete footings at a deeper level. It's commonly required when converting a low-ceiling basement into a legal dwelling unit.
When is underpinning required for a basement apartment?
If your existing basement ceiling height is below 1.95 metres (6 feet 5 inches), underpinning or bench footing is typically required to achieve the minimum height for a legal dwelling unit under the Ontario Building Code.
What is the difference between underpinning and bench footing?
Underpinning extends the foundation deeper and preserves the full floor area at the new lower level, giving the most usable height. Bench footing adds an angled concrete bench inside the foundation - it is cheaper and faster but reduces the floor area around the perimeter. We recommend the right option for your foundation, budget, and water table.
Does basement underpinning need a structural engineer?
Yes. Underpinning temporarily removes support from a loaded foundation, so it always requires a Professional Engineer (P.Eng) to design the footings, reinforcement, and excavation sequence. Ontario Design Studio coordinates the permit drawings and the structural engineering under one package.