A home addition in Richmond Hill costs $250 – $650 per square foot fully built in 2026: single-storey rear or side additions run $250 – $500/sq ft, and second-storey additions $300 – $650/sq ft. In Richmond Hill, what most often changes an addition's design and schedule is not the structure but the lot: the City's tree by-law now protects private trees from 15 cm in diameter, heritage-designated houses need a heritage permit for exterior work, and north-end lots on the Oak Ridges Moraine can need conservation approval. This guide covers those steps along with costs and timelines.
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Home Addition in Richmond Hill: Key Takeaways
- Trees first: since April 2025, injuring or removing a private tree 15 cm or wider needs a permit. Footings, excavation and even material storage over a root zone count as injury, so an arborist's plan usually comes before the architect's final drawings.
- Heritage: exterior changes to a designated heritage house, many near the old village core and the Mill Pond, need a heritage permit.
- Oak Ridges Moraine: lots in the north end near lakes, woodlots and wetlands can need conservation authority approval.
- Units: an addition can be designed to hold an additional residential unit, now permitted where detached, semi-detached and townhouse dwellings are allowed.
- Variances: designs beyond setback, height or coverage limits need a minor variance from the Committee of Adjustment, which adds months.
Home Addition Costs in Richmond Hill (2026 CAD)
| Project | Per sq ft | Typical total |
|---|---|---|
| Bump-out (kitchen or mudroom, under 200 sq ft) | $300 – $550 | $45,000 – $110,000 |
| Single-storey rear or side addition, about 300 sq ft | $250 – $500 | $75,000 – $150,000 |
| Second storey over a 1,200 sq ft main floor | $300 – $650 | $360,000 – $780,000 |
| Rear addition with a basement below | $300 – $550 | add 20 – 35% for excavation and foundation |
Totals include structure, envelope, mechanical and finishes, but not design fees, arborist reports, variance costs or work in the existing house. Ground-up custom homes are built with our licensed builder partner; see home additions and custom builds.
Planning an Addition on a Richmond Hill Lot
Mature trees and the 15 cm rule
Under Tree Preservation By-law 19-25, the permit threshold dropped from 20 cm to 15 cm in April 2025, so many more trees on a typical lot are now protected, and replanting securities are required before a permit is issued. On larger lots with mature trees, the tree protection zones often decide where a rear addition can go, or whether going up is the better option.
Heritage houses
For a designated house, the addition's size, materials, rooflines and windows are reviewed for fit with the heritage building. Additions set back from the original and clearly distinguishable from it are the usual approach. We check the City's heritage register for the address before design.
Oak Ridges and conservation lands
Near Lake Wilcox, the kettle lakes, woodlots and wetlands of the Oak Ridges Moraine, and along valleys and watercourses, grading and building can need a permit under the Conservation Authorities Act and must fit the Moraine's planning limits. This is checked at feasibility, before drawings.
Second storeys
Adding a storey keeps the footprint, which avoids most tree and setback issues, but an engineer must confirm the existing footings and walls can carry it. Height limits in the zoning by-law also apply, so we confirm them before design.
How a Richmond Hill Addition Project Runs
- Free site visit. We measure, look at the foundation and structure, and check trees, heritage status, conservation mapping and zoning.
- Feasibility and fixed-price quote within 5 business days. Including whether a tree permit, heritage permit or variance is likely.
- Arborist, design and engineering. Tree protection plan, architectural drawings and structural design.
- Approvals. Tree, heritage, conservation and variance approvals first, then the building permit. The Ontario Building Code gives the City 10 business days to decide on a complete house application.
- Build. One project manager from excavation or roof removal to final inspection.
- Inspections and handover. City and ESA inspections passed, site cleaned.
Frequently Asked Questions
How much does a home addition cost in Richmond Hill?
A single-storey addition costs $250 – $500 per square foot, about $75,000 – $150,000 for 300 sq ft. A second storey runs $300 – $650 per square foot.
Will I need a tree permit for my addition?
Very likely if there is a tree of 15 cm or more near the work area, on your lot or a neighbour's. Excavation in a tree's root zone counts as injuring it.
Can my addition include a separate unit?
Often, yes. Additional residential units are permitted where detached, semi-detached and townhouse dwellings are allowed, subject to the zoning standards, and the unit must meet the Building Code and Fire Code.
How long does a home addition take in Richmond Hill?
A single-storey addition usually takes 6 – 14 months from first design meeting to final inspection, and a second storey 11 – 21 months. Tree, heritage and conservation approvals and variances make the long end of those ranges.
Get a Free Quote in Richmond Hill
Country Renovations has been building additions across Richmond Hill and the GTA since 2014. WSIB-covered trades. $5M insured. Book a free site visit and you will receive a written, fixed-price quote in 5 business days.