The 10% Accessory Coverage Rule
In many residential-lot scenarios, the total footprint of accessory structures can become the limiting factor. Count the detached ARU alongside existing sheds, detached garages, pool houses, and other accessory buildings before assuming a large lawn equals unlimited room. If lot coverage looks tight, compare the broader ARU zoning guide and R1-7 lot coverage guide.
- Measure existing accessory structures before sizing the ARU.
- Confirm whether old sheds or detached garages should be removed before design.
- Leave contingency for zoning interpretation and permit review.
Trenching Across Deep Yards
Deep suburban yards can add real cost because water, sanitary, hydro, gas, internet, drainage, and restoration may need longer routes. A generous backyard can still be expensive if services are far from the proposed unit or if trenching crosses patios, trees, retaining walls, pools, or finished landscaping.
For Byron, Westmount, and Oakridge properties, servicing distance can be the line item that turns a simple concept into a careful budget decision.
FAQ
Common questions, answered plainly
Does a large London lot automatically work for an ARU?
No. A large lot can still run into accessory coverage, setbacks, servicing, tree, drainage, or permit issues. Measure the existing structures before choosing the ARU size.
Why are utility runs important on suburban ARU lots?
Longer service runs can add trenching, restoration, engineering, and coordination costs. The distance from the main house to the proposed unit should be reviewed early.
Check Coverage And Services First
Use the audit tool to flag whether the lot looks strong on paper before you price a suburban backyard suite.
Run The ARU Audit