Part 4 of the Ontario Building Code, referencing the National Building Code of Canada (NBCC), sets clear expectations for foundation performance on marginal ground. In Markham, where pockets of glaciolacustrine clay and silt dominate the subsurface south of Highway 7, traditional shallow footings often hit a wall, literally and figuratively. The Don River watershed corridor, which cuts through the city’s east side, compounds the challenge with water tables sitting barely two meters below grade. Stone column design steps in when excavation and replacement becomes impractical, offering a vibro-replacement path that densifies the matrix and creates vertical drains. A proper grain size analysis of the native soil is the first filter to confirm that fines content won't choke the stone column's drainage function, while site-specific CPT testing maps the undrained shear strength profile needed to size the columns.
A well-designed stone column grid in Markham's soft clay can cut post-construction settlement by 60 to 80 percent compared to untreated ground.
Applicable standards
NBCC 2020 (National Building Code of Canada), CSA A23.3 Design of Concrete Structures, ASTM D4123 Tensile Characteristics of Bituminous Pavement, OPSS 1010 Aggregates – Base, Subbase, Select Subgrade, Ontario Building Code – Supplementary Standard SB-1
Frequently asked questions
How much does stone column design cost for a Markham project?
For a typical commercial or industrial building in Markham, the engineering design package — including geotechnical interpretation, stone column modeling, construction specifications, and QA/QC oversight — ranges from CA$2,050 to CA$6,890. The spread depends on the treated area, number of columns, and depth of the soft layer. A 1,500 m² footprint with 8 to 12 meters of soft clay will land near the middle of that range.
What soil types in Markham are best suited for stone columns?
Stone columns perform well in the soft to firm silty clays and clayey silts common to Markham's glaciolacustrine plain, particularly where the undrained shear strength is at least 15 to 20 kPa. They also work in loose silty sands where vibrocompaction alone may not achieve the target density. Sites with thick organic deposits or peat, such as filled-in wetlands near the Rouge River headwaters, usually require a different approach or excavation and replacement before column installation.
What's the difference between stone columns and vibrocompaction?
Vibrocompaction densifies granular soils by rearranging particles under vibration without adding stone. Stone columns, by contrast, actually displace soft cohesive soil and replace it with a compacted granular column. In Markham's mixed stratigraphy — where sand lenses alternate with silty clay — we often use a combination: vibrocompaction for the sandy zones and stone columns for the cohesive pockets, all within the same treatment grid.
How long does the design process take from field investigation to final drawings?
A realistic timeline for a Markham project runs about four to six weeks. The first two weeks cover the CPT and test pit campaign to map the soft layer thickness and water table. Modeling and design take another two weeks, and the final week covers review, drafting of construction specs, and coordination with the structural engineer. Projects requiring a peer review or municipal permit add roughly one extra week.
