Buying to Renovate or Expand in Town of Mount Royal: What to Check Before You Sign

Recently, a buyer visited a house we had listed in Town of Mount Royal. Within the first few minutes, they fell for it: the street, the charm of the property, the feel of the neighbourhood, it was all there. Or almost. Two important things were missing: a garage and a primary suite. Like many buyers would have, they wondered whether they could simply add them by expanding.

It's a question we hear often, and it's a perfectly legitimate one. But the answer is never automatic, especially when the house is a century old and its architectural features matter to the Town. An older house doesn't necessarily have official heritage status. Its age is still a reason to check which protections and criteria apply. Before picturing yourself in it, the best reflex is to present your intentions to the urban planning department and have their feasibility assessed.

In what follows, we go over what to check before betting on a house's potential: zoning rules, the well-known PIIA, work that requires a permit even without an expansion, and approval timelines. Four municipal council decisions also show, very concretely, why these checks are worth doing before you sign.

Start with zoning

Each zone has its own rules: setbacks, maximum height, volume, lot coverage. So a big yard doesn't mean you'll be able to build over its whole surface. And just because the neighbour expanded doesn't mean you'll get the same.

The certificate of location is a good starting point. It shows where the buildings sit on the lot and brings out any servitudes that could get in the way of a project. The Town also requires it for any permit application or zoning review. That's often where you see the difference between the space available and the space you can actually build on.

The PIIA: the step many people underestimate

Meeting the permitted dimensions isn't enough. In the Town of Mount Royal, new construction, expansions and work that changes a building's exterior appearance must be approved under a site planning and architectural integration programme (PIIA, its French acronym).

The application can be demanding: plans, elevations, 3D renderings, material samples, photos. For an expansion, you even have to show the trees on the lot. The Town wants to see how the project fits with the existing house and the neighbourhood.

If you plan to transform the house in depth, find out early which architectural features will have to be preserved.

You don't need to expand to need a permit

Changing the exterior cladding or the roof may also require authorization. Routine maintenance is exempt under certain conditions, notably if there is no structural change and no change to certain architectural details.

Inside, a permit is required as soon as the work affects the structure or changes the number of dwelling units. Removing a load-bearing wall is therefore one of the things to check, even if nothing changes on the outside.

Plan for approval timelines

A project subject to the PIIA goes through several steps. The urban planning department first checks that it complies. The planning advisory committee then issues a recommendation, and the municipal council makes the decision. The permit is issued only once all conditions are met. A preliminary meeting with the planning department helps identify the constraints, but it guarantees nothing.

Four refusals that give pause

The council's public decisions clearly show the limits a project can run into. Civic numbers have been withheld.

Thornton: building over the garage isn't a given. On May 15, 2017, the council refused an expansion above the garage and on the second floor. The volume overwhelms the house, the butterfly roof clashes with the existing building and the PIIA criteria for semi-detached houses are not met. The Town suggests a setback. Having a garage doesn't guarantee you'll be able to build on top of it.

Trenton: a complete change of style can be a roadblock. The same evening, a project for partial demolition, a rear expansion and a redesign of all four façades was refused. It fits poorly with the surrounding homes, and its style must reflect the phase II models of the PIIA. If you dream of a transformation, have the idea validated before making it a condition of your purchase.

Graham: you may be asked to keep the original materials. On February 18, 2025, a change to the façades was refused. The proposed stone makes the house look heavier, and the council requires that the aluminum siding and brick, which contribute to its character, be kept.

Marlboro: even a chimney counts. The same day, the removal of a chimney was refused. The council found the work unjustified and the original feature important to the house's architecture. A seemingly minor detail can therefore sink a project.

Before you sign, ask the question

These decisions concerned specific projects, on specific dates. They don't mean that any future work on these houses would be impossible. But they're a reminder that it's better to talk about your intentions from the very first visits, as our buyer did. A garage, a primary suite, an extra storey: if that project weighs in your decision, check it before you put a value on it.

Your broker can help you gather the documents and guide your checks with the Town and the relevant professionals. It's often this step, taken at the right time, that lets you buy with your heart without any unpleasant surprises.

Source: Town of Mount Royal, ville.mont-royal.qc.ca (urban planning by-laws and council minutes, in French).