What is Considered a Home Extension in Montreal

A home extension is any structural change that increases your usable living space or the volume of your house, beyond simple interior remodeling. It usually alters the building envelope (its outer shell) and often requires foundations, structure, and municipal approval.

Core Definition

A project generally counts as a home extension when:

• It adds new square footage to the house (horizontally or vertically).

• It changes the footprint or height of the building (new volume, not just layout changes inside).

• It requires structural work (new foundations, load-bearing walls, beams, or roof framing).

• It affects the exterior envelope (walls, roof, openings) rather than only interior finishes.

By contrast, painting, changing cabinets, or moving non‑structural partitions are renovations, not extensions.

Main Types of Home Extensions

These are the most common forms of home extensions in Quebec and Montreal.

• Side (lateral) extension: Built on the side yard to enlarge rooms like the kitchen, living room, or add bedrooms; it extends the ground floor and changes the footprint.

• Rear extension: Added at the back of the house to create a larger kitchen, dining room, family room, or solarium, often keeping the front façade intact.

• Rear extension: Added at the back of the house to create a larger kitchen, dining room, family room, or solarium, often keeping the front façade intact.

• Vertical extension (adding a floor): Adds an extra storey to a bungalow or low-rise home, effectively doubling living area without losing yard space.

• Garage expansion or transformation: Expands a garage or converts it (and sometimes adds a floor above) into heated, habitable space.

• Sunroom or glass extension: A four-season veranda or solarium structurally attached to the house, designed as living space, not a temporary enclosure.

• Basement expansion / digging down: Excavating to increase basement height or extend under the house, creating new livable area below grade.

All of these change the overall volume of the home, so they are treated as extensions or additions, not simple renovations.

What Is Not a Home Extension?

Some projects feel big but do not technically count as extensions.

• Interior remodeling that stays within existing walls (new kitchen, bathroom, flooring, or partitions).

• Finishing an unfinished basement without modifying foundations or footprint.

• Replacing windows, roofing, or siding without enlarging the building or creating new enclosed space.

These can still require permits, but they usually fall under renovation rather than extension categories.

Why the Definition Matters

Understanding what counts as a home extension helps you:

• Know when you’re entering “major work” territory that needs structural design and municipal approval.

• Budget more accurately, since extensions typically cost more per square foot than interior renovations due to foundations and structure.

• Choose the right professionals (architect, engineer, licensed contractor) and follow the proper process from planning to permits.

For a Montreal‑focused blog, you can keep this structure, then add a note that local boroughs treat any addition that changes footprint, height, or habitable area as an extension that must be declared and approved.

For more information

Lineaire General Contractor, can also advise you on your project, with its team of carpenters and joiners. You can contact them via their website: www.lineaireconstruction.com or on social media @lineaire.entrepreneur.general

What is considered a Home Extension in Montreal