Built to spec
Built to your engineered drawings, survey, and the real site conditions, not a one-size-fits-all approach forced to fit.
Commercial & Heavy-Civil Construction
Mass Concrete Underpinning
Harrowgate Group directly completes mass concrete underpinning for developers, general contractors, engineers, and commercial property owners across Toronto, the GTA, and Ontario, coordinating investigation, engineered support, construction, testing, monitoring, and load transfer.
- Licensed, Insured & WSIB-Covered
- 20 Years in Business
Get a Quote
Tell us what you need and we’ll get you a quote. Licensed, insured & WSIB-covered · Free, no-obligation quote & on-site assessment.
Get a Quote
Licensed, insured & WSIB-covered · Free, no-obligation quote & on-site assessment.
20 Years in Business
Licensed, Insured & WSIB-Covered Completed to code & Ontario requirements Completed on site and built to the drawings Performed & installed on site across Ontario
Why Harrowgate Group
What to expect from mass concrete underpinning
Made to last
Durable materials and methods chosen for the load, traffic, and environment on site.
Quote-ready
Send specs, drawings, or photos and get a free, no-obligation site visit and estimate with no guesswork.
Code-conscious
Installation and site work completed in accordance with Ontario requirements.
Our Process
How we plan and deliver mass concrete underpinning
Mass concrete underpinning deepens an existing strip or wall footing with short, alternately excavated concrete pins that bear on competent soil and connect tightly to the old foundation. Harrowgate constructs numbered underpinning pits for commercial and institutional buildings across Toronto and the GTA, controlling excavation, bearing, concrete placement, curing, and final load transfer.
- 01 Send your inquiry, a few photos or a description of the site.
- 02 We come out, assess the site, take measurements, and confirm the scope.
- 03 We complete the mass concrete underpinning on site, to the load and finish the job needs.
- 04 We install it, finish to grade, and clean up, one accountable crew, start to finish.
Local Context
A closer look at mass concrete underpinning
Scope
Understanding mass concrete underpinning
How we deliver mass concrete underpinning
Underpinning succeeds when the temporary load path is defined before soil or concrete is removed. We establish survey control, verify services and existing geometry, build only the authorised stage, keep excavations stable and reasonably free of water, inspect concealed work, and transfer load only after the new support has reached the engineer's stated acceptance criteria.
The wall is divided into pit numbers on the engineer's drawing, typically arranged so first-stage pins are separated by untouched ground. We expose only the authorised pin, shore its sides, and excavate below the footing without removing adjacent support. The bottom is trimmed level and protected from rain, seepage, frost, and traffic.
After inspection, concrete is placed from the new bearing level to the specified gap below the existing footing and consolidated without washing soil from the sides. Once concrete reaches the stated strength, the final gap is tightly dry packed or pressure filled with the specified material. Later stages proceed only in the numbered order.
Every active element has an identity, status, and release condition. Daily records show what was exposed, the soil or founding response, temporary support, water, dimensions, materials, inspections, concrete or grout placement, strength evidence, pile or jack data where applicable, and movement readings. An unexpected condition is stabilized and reviewed before the opening is enlarged or the next stage begins.
Materials, specs, and Ontario standards
Every dimension and capacity comes from the sealed structural and geotechnical design, not a field rule of thumb. We control founding elevation, open length, pile or bearing capacity, reinforcement, steel, concrete and grout, load-transfer contact, sequence, testing, inspection, and movement. Applicable OBC provisions, Ontario construction requirements, CSA standards, and project-specific OPSS clauses govern the work.
The design fixes pin width, depth, maximum open length, stage pattern, socket or key geometry, reinforcing where required, concrete class, strength before transfer, and dry-pack or grout requirements. Some pins are plain mass concrete, while others contain dowels, cages, shear keys, or a reinforced cap depending on loads and geometry.
Applicable OBC and CSA concrete requirements govern materials and placement. Ontario excavation rules govern soil support, water removal, access, adjacent structures, surcharge, and inspection. We log excavation dates, bearing approval, dimensions, concrete tickets, cylinders where specified, transfer material, and closure date for every pin.
Ontario construction rules require services to be located and marked before excavation, hazardous services to be controlled, adjacent structures to receive the written precautions specified by an engineer, and worker excavations to be reasonably free of water. Soil, surcharge, safe access, edge protection, and support systems are managed as part of the underpinning operation, not left outside the foundation detail.
What goes wrong, and how we prevent it
The failures buyers worry about are settlement, cracking, loss of bearing, unstable excavations, damaged services, incomplete contact, failed pile or concrete tests, water entry, and schedule delay. These problems usually begin at a concealed interface or an out-of-sequence opening. We prevent them with early exposure, numbered stages, engineered temporary support, documented inspections, strength holds, measured transfer, and monitoring.
The method is vulnerable to running soil, water entering the bearing surface, over-excavation, adjacent pins opened at once, honeycombing beneath the old footing, early dry packing, and shrinkage or incomplete contact at the load-transfer joint. A deep pit can also undermine a nearby column or service outside the visible wall line. We prevent these failures through investigation openings, strict pit numbering, short exposure time, local sheeting, pumps with filtered collection, clean placement access, specified strength holds, and inspection of the final joint.
Weather, pumping, vibration, building use, material storage, and work by other crews can change the temporary condition. We review those influences each shift. If a movement level, test criterion, bearing requirement, or inspection hold is not satisfied, the affected work stops, remains supported, and is referred to the engineer before load or excavation progresses.
Have drawings for mass concrete underpinning? Send them over and we will scope it.
FAQ
Mass Concrete Underpinning FAQ
How is mass concrete underpinning sequenced?
We sequence mass concrete underpinning from the sealed drawings and the existing load path. The wall is divided into pit numbers on the engineer's drawing, typically arranged so first-stage pins are separated by untouched ground. Each stage remains within its stated opening limit, receives the specified support and inspection, and reaches its concrete, grout, pile, connection, or transfer acceptance condition.
Does underpinning always require a building permit and engineered drawings?
Commercial underpinning is structural work and is planned from sealed engineering documents. Permit and submission requirements depend on the municipality and full project scope, but excavation, foundation changes, temporary support, and load transfer must be coordinated with applicable OBC requirements and approved documents. We confirm required inspections and hold points before opening the first stage.
How do you determine which underpinning method to use?
The selection follows existing loads and condition, footing geometry, soil and groundwater, depth to competent support, access, headroom, vibration limits, neighbouring assets, property rights, and the proposed permanent work. Shallow competent bearing may suit concrete pins. Deep weak soils or concentrated reactions may require piles, beams, brackets, needles, or ground treatment.
Can the building remain operational during underpinning?
Often it can, when the engineer's temporary load path and the project phasing support continued use. We isolate work zones, maintain required exits and services, control dust, noise, vibration, and deliveries, and schedule disruptive transfers around operations. Feasibility depends on structural condition, access, sensitive equipment, utility interruptions, and the response plan for unexpected movement.
How do you monitor movement during the work?
We establish baseline elevations and condition observations before disturbance, then read the specified survey points, crack gauges, tilt points, or other instruments at stage and time intervals. Results are compared with engineer-defined review and action levels. A rapid change, unusual trend, or visible distress triggers confirmation, stabilization, notification, and a hold on affected work.
What happens if the existing footing differs from the drawings?
We keep the exposed area stable, document dimensions and material condition, and notify the engineer before extending demolition or excavation. Footing depth, width, reinforcement, masonry quality, hidden grade beams, services, and previous alterations can change the load-transfer detail. The affected stage continues only after the design is confirmed or revised for the observed condition.
What are the main schedule and cost drivers?
The main drivers are investigation findings, number and depth of stages, soil and groundwater, working headroom, hand excavation, temporary support, pile depth, drilling obstructions, structural steel, reinforcing, concrete and grout, load testing, monitoring, inspection timing, spoil routes, occupied operations, and reinstatement. A complete sequence and early exposures reduce uncertainty before full production begins.
What closeout records are available?
The project package can include investigation records, pit or pile logs, bearing approvals, reinforcement inspections, concrete tickets and test results, grout records, steel and connection inspections where specified, pile tests, jacking and preload readings, monitoring plots, field changes, photographs, and as-built locations. The final list follows the project specification and engineer's inspection plan.
Still have a question about mass concrete underpinning? Ask our team directly.
Explore
Related Harrowgate services
Foundation underpinning, Foundation underpinning for general load transfer
Micropiles, Micropiles for deep support and restricted access
Underpinning, Underpinning for occupied commercial properties
Support beside deep excavation, Support beside deep excavation
Movement monitoring and trigger-level reporting, Movement monitoring and trigger-level reporting
Our Work
View Our Projects See real projects across Toronto & Ontario
Commercial and heavy-civil construction delivered for developers, contractors, property managers, and municipalities.
Get a quote for mass concrete underpinning
Send drawings, a site plan, or a description of the scope. Harrowgate Group is licensed, insured, and WSIB-covered.
Licensed, Insured & WSIB-Covered, work managed and documented on every job
Send your project details
Tell us what you need and we’ll get you a quote. Licensed, insured & WSIB-covered · Free, no-obligation quote & on-site assessment.
Mass Concrete Underpinning Across the GTA
View all service areas →Harrowgate Group provides mass concrete underpinning, delivered and installed with quote-ready support across Toronto and surrounding Ontario communities.
