Building a multiplex over an underground parkade: what we've learned in Coquitlam and Burnaby
- Putting parking underground frees the ground for homes, yards and trees instead of driveways and garages.
- On our projects the parking and storage level did not count toward the lot's allowable floor area. That depends on the bylaw, so check yours.
- It costs more and takes longer than a slab-on-grade multiplex. The key risks are excavation, shoring, groundwater and waterproofing.
- It suits larger lots (roughly 9,000 sq ft and up), sloping sites and projects aiming at family-sized homes.
Two projects, one approach
| 1161 Madore Ave, Coquitlam | 850 Duthie Ave, Burnaby | |
|---|---|---|
| Lot | 9,849 sq ft, RT-1 | 11,527 sq ft, R1 small-scale multi-unit housing |
| Homes | 4 homes, about 1,835 to 1,856 sq ft | 6 homes in 3 duplexes, about 2,540 to 2,790 sq ft |
| Below ground | Parking and storage level, about 4,770 sq ft, 8 stalls | Parkade about 5,112 sq ft, 8 stalls with EV chargers |
| Status | Under construction, completion expected summer 2027 | Coming fall 2028 |
Why go underground?
More of the lot for living
Surface parking, driveways and garages can take a large share of a multiplex lot. Below ground, that space becomes yards, patios, trees and room between buildings. At 850 Duthie, for example, the three duplex buildings sit about 8 m apart over a shared parkade.
Floor area that goes to homes
Many multiplex bylaws cap floor area (FAR) and lot coverage. At 1161 Madore the parking and storage level was exempt from the floor area calculation. That let the full allowable floor area go to the homes above.
Homes buyers want
Families moving from a detached house usually want a secure garage, storage and an EV charger. A parkade delivers all three without a row of garage doors on the street.
What makes it harder
- Excavation and shoring. Digging a full level near property lines needs an engineered shoring design, monitoring and care for neighbours' foundations, services and trees.
- Groundwater and waterproofing. Below-grade walls and the slab need a continuous waterproofing system and drainage. A leak after the homes are finished is expensive to fix.
- Fire and life safety. The parkade is usually treated as a separate building from the homes above, with fire-rated concrete separations, exits and, often, sprinklers.
- Ramps and grades. Ramp slopes, the clearance at the street and turning space for cars set much of the layout.
- Utilities. Electrical rooms, EV charging, exhaust and drainage all need space and coordination with the utility.
- Cost and time. Expect a larger budget and a longer schedule than slab-on-grade. Underground work is also where surprises happen, so a contingency matters.
How long the below-ground work took at 1161 Madore
| Stage | Timing |
|---|---|
| Site preparation | December 2025 to January 2026 |
| Excavation and shoring | February to June 2026 |
| Foundation | June to July 2026 |
| Parkade slab | August to September 2026 |
| Framing | Next stage, fall 2026 |
You can follow the build on the 1161 Madore progress page.
When a parkade makes sense
- The lot is large enough for a ramp and drive aisle, roughly 9,000 sq ft or more for a fourplex.
- The site slopes, so part of the level is already below grade.
- The project targets family homes where parking and storage add real value.
- Soil and groundwater conditions are reasonable, which a geotechnical report confirms early.
On smaller or flat lots, or near SkyTrain where parking may not be required, surface parking or no parking can be the better choice. Run the numbers both ways.
How we manage the risk
Red Cedar manages construction through Vanguard Civil & Construction, our construction management arm. We bring the geotechnical engineer, structural engineer and excavation and shoring trades together early. We tender the trades and track cost, schedule and quality through the below-ground stages, where most of the risk sits.
Thinking about a multiplex on your lot?
Send your address and lot size to inquiry@redcedarproperties.ca or call 604-396-3682.
Figures come from the permit drawings for each project and are approximate. This article is general information, not engineering advice.