# Large Detached Deep Lowering Project in Richmond Hill, ON | Toronto Basement Underpinning URL: https://torontobasementunderpinning.ca/basement-underpinning/richmond-hill/large-detached-deep-lower/ Documented Project: Richmond Hill, York Region # Large Detached Deep Lowering Project in Elgin Mills, Richmond Hill Deep lowering for a legal duplex conversion required the maximum allowable depth under local soil-bearing capacity and continuous engineering oversight. Completed by Toronto Basement Underpinning [/ →](/) in August 2024. Fixed-price contract, engineered drawings and York Region permit coordination included. Book a Call About Your Project [/contact/ →](/contact/) Call (416) 900-3329 [tel:+14169003329 →](tel:+14169003329) Licensed & Insured Free Estimate Within 2 Hours Workmanship Warranty on Every Project GTA-Wide Service ![Large Detached Deep Lowering worksite in Elgin Mills, Richmond Hill, ON - Full perimeter deep lowering for legal duplex](/images/combos/project-cards/richmond-hill-4.webp) KEY STATS Project Success Metrics Delivered on time and within budget 9.9/10 Total project cost $75,000 Local labor 80% Local supplier spend 100% Building Stats Basement size 1,420 sqft New area gained 1,180 sqft Linear footage underpinned 180 lin ft Pins poured 32 Depth gain 2'10" Original ceiling 5'2" Finished ceiling 8'0" Client Homeowner in Richmond Hill Completion August 2024 Location Elgin Mills, Richmond Hill, ON Sector Residential Permit turnaround 10 weeks Warranty 10 years ## Introduction Deep lowering for a legal duplex conversion required the maximum allowable depth under local soil-bearing capacity and continuous engineering oversight. The property is a residential detached in Elgin Mills, Richmond Hill, with an original 5'2" basement ceiling across a 1,420 sqft footprint. Our crews delivered a full perimeter deep lowering for legal duplex project under a fixed-price contract that bundled engineered drawings, York Region permit coordination, excavation, pin-by-pin underpinning, interior waterproofing, and new slab pour. The scope lowered the basement by 2'10" to deliver a 8'0" finished ceiling across 1,180 sqft of newly usable standing-height basement area, directly enabling the homeowner's plan for a legal secondary use of the lower level. ## The Underpinning Process A controlled sequence of engineered steps delivered the Elgin Mills project on time and within budget. Each phase passed York Region inspection before the next began. ### 1\. Deep Assessment and Full Engineering Deep-lowering projects require geotechnical confirmation of soil-bearing capacity to the target footing depth, written structural engineering sign-off, and settlement monitoring plan filed with the municipality before mobilisation. ### 2\. Excavation Pin-by-pin excavation along 180 linear feet of perimeter to 2.83 feet below the original slab. Strict alternating segment sequence to maintain continuous support. ### 3\. Underpinning Pits Mass-poured concrete footings at the maximum depth allowed by the soil assessment, each pit confirmed by the structural engineer before pour. ### 4\. Steel Reinforcement Heavy 15M rebar cages with additional lateral ties for deep-column load transfer. Vertical dowels tied into the retained upper footing. ### 5\. Structural Supports and Settlement Monitoring Full-structure monitoring instrumentation installed and read daily. Settlement maintained within engineered tolerances throughout the six-week on-site phase. ### 6\. Waterproofing and Drainage Full perimeter interior Delta-MS, perforated weeping tile, dual sump pits with battery backup, and backwater valve installation on the main sewer connection. ### 7\. Insulation and Finishing New engineered slab poured over vapor barrier. Basement now has an 8-foot standing ceiling across the full 1,180 sqft of new living area, ready for legal duplex finishing trades. ## Our Approach Delivered on time and within budget. The Elgin Mills project ran through several site challenges: oak ridges moraine ecological overlay across the north end of richmond hill drives higher groundwater tables and demands enhanced interior waterproofing on any underpinning scope, while bayview hill estate lots have deeper native footings. We addressed each early by sourcing locally where material shortages hit, scheduling around weather windows, and running hydraulic jacks plus specialised concrete mixes during the deepest excavation phase. Modern waterproofing membranes replaced the aging drainage components, and the result is a basement that is both structurally sound and dry. ## What's Included in This Project Scope The fixed-price contract covered every item below. No line-item surprises, no change orders unless the homeowner added scope. One contract, one warranty, one crew. - Deep-lowering geotechnical soil-bearing capacity assessment - Full engineering package with settlement monitoring plan - City permit application and inspection coordination - Pin-by-pin excavation to maximum engineered depth - Mass-poured concrete footings with engineer sign-off per pit - Heavy 15M rebar cages with additional lateral ties - Full-structure monitoring instrumentation with daily reads - Full interior perimeter Delta-MS and perforated weeping tile - Dual sump pits with battery backup and backwater valve - Engineered reinforced slab pour over vapor barrier - Workmanship warranty on all structural work ## Social Impact Local engineer, local structural monitoring, local waste-haul trades, and 100% of structural materials sourced from Ontario suppliers. Reduced project transport footprint by an estimated 400 vehicle miles compared to an out-of-city crew. ## Client Testimonials Rated 4.9 stars across projects documented on the site. > ★★★★★ > > "" > ★★★★★ > > "" > ★★★★★ > > "" ## Thinking About Underpinning in Richmond Hill? Every project on this site is delivered on a fixed-price contract with engineered drawings, York Region permits, and a workmanship warranty included. The scope of your project may differ from this one - we size the quote to your actual building, soil, and depth-gain goal. Book a free site assessment and we respond within two business hours. Book a Free Site Assessment [/contact/ →](/contact/) Call (416) 900-3329 [tel:+14169003329 →](tel:+14169003329) ### Other Documented Richmond Hill Projects - Partial Crawl-Space Underpinning in Richmond Hill [/basement-underpinning/richmond-hill/partial-crawl-space-underpin/ →](/basement-underpinning/richmond-hill/partial-crawl-space-underpin/) - Single-Wall Shallow Underpinning in Richmond Hill [/basement-underpinning/richmond-hill/single-wall-shallow-underpin/ →](/basement-underpinning/richmond-hill/single-wall-shallow-underpin/) - Semi-Detached Shared-Wall Underpinning in Richmond Hill [/basement-underpinning/richmond-hill/semi-detached-shared-wall-underpin/ →](/basement-underpinning/richmond-hill/semi-detached-shared-wall-underpin/) - Heritage Rubble-Stone Foundation Underpinning in Richmond Hill [/basement-underpinning/richmond-hill/heritage-rubble-foundation-underpin/ →](/basement-underpinning/richmond-hill/heritage-rubble-foundation-underpin/) - Commercial Café Underpinning in Richmond Hill [/basement-underpinning/richmond-hill/commercial-cafe-underpin/ →](/basement-underpinning/richmond-hill/commercial-cafe-underpin/) ### Same Project Type in Other Cities - Large Detached Deep Lowering in Toronto [/basement-underpinning/toronto/large-detached-deep-lower/ →](/basement-underpinning/toronto/large-detached-deep-lower/) - Large Detached Deep Lowering in Mississauga [/basement-underpinning/mississauga/large-detached-deep-lower/ →](/basement-underpinning/mississauga/large-detached-deep-lower/) - Large Detached Deep Lowering in Etobicoke [/basement-underpinning/etobicoke/large-detached-deep-lower/ →](/basement-underpinning/etobicoke/large-detached-deep-lower/) - Large Detached Deep Lowering in Scarborough [/basement-underpinning/scarborough/large-detached-deep-lower/ →](/basement-underpinning/scarborough/large-detached-deep-lower/) - Large Detached Deep Lowering in North York [/basement-underpinning/north-york/large-detached-deep-lower/ →](/basement-underpinning/north-york/large-detached-deep-lower/)