How do I add a second storey to my existing single-storey garage in Riverview NB?

Adding a second storey to an existing single-storey garage in Riverview is a major structural project — and in most cases, the existing garage was never engineered to carry the loads a second floor demands, which means the foundation, walls, and roof all need professional assessment before any planning begins.

This is one of the more complex garage renovation projects a homeowner can undertake, and the honest answer is that it sits somewhere between a full renovation and a new build in terms of cost, complexity, and risk. Here's what you need to understand before moving forward.

The Structural Reality

The biggest challenge with adding a second storey to an existing garage is that single-storey garages are typically built to carry only their own roof load — roughly 2.4 to 4.8 kPa of snow load in the Riverview area, plus the dead load of the roof structure itself. Adding a full second floor means the walls, foundation, and footings suddenly need to carry floor live loads (typically 1.9 kPa for residential use), the weight of the new floor structure, the new walls above, and a new roof — all stacked on top of a structure that was never designed for it.

The existing wall framing (likely 2x4 or 2x6 studs at 16 inches on centre) may or may not be adequate for the added load. The existing foundation is the bigger concern. Most single-storey detached garages in Riverview are built on relatively modest footings — often 16 inches wide by 8 inches thick — which may be undersized for a two-storey structure. Before you spend a dollar on design or materials, you need a structural engineer to assess the existing foundation, footings, wall framing, and connection details. This assessment typically costs $500–$1,500 and is money you cannot skip.

What the Assessment Will Tell You

A structural engineer will evaluate whether your existing footings can carry the additional load, whether the frost walls are deep enough (Riverview requires foundations below the frost line — minimum 4 feet), whether the existing wall studs need to be sistered or replaced, and whether the existing garage door header can remain or needs to be upgraded to an LVL beam. In many cases, the engineer will require the footings to be underpinned or the foundation to be partially rebuilt — particularly if the original garage was built on a thickened-edge slab rather than full frost walls. Underpinning is expensive ($10,000–$25,000 range) but is sometimes the only safe path forward.

If the foundation assessment comes back clean, the project becomes much more straightforward: remove the existing roof, install a new floor system (typically engineered I-joists or LVL beams spanning the garage width), frame the second-storey walls, and build a new roof above. The new floor system needs to be designed for NB's snow loads and the intended use of the upper space.

Permits and Riverview Zoning

You will need a building permit from the Town of Riverview for this project — no exceptions. Adding a storey to an existing structure is a major structural alteration that triggers full building code review. The permit application will require drawings showing the existing structure and proposed additions, and in most cases a structural engineer's stamp on the drawings will be required or strongly recommended by the building department.

Check Riverview's zoning bylaws for maximum building height in your zone before committing to the design. Residential zones in Riverview typically cap accessory structures (detached garages) at a specific height — often 5 to 6 metres to the peak — and a two-storey garage may push against or exceed that limit depending on your existing structure's height. A quick call to the Town of Riverview planning department (506-387-2020) before you hire an engineer will confirm whether the project is even permitted under current zoning.

Realistic Cost Range

If the foundation and existing walls are deemed adequate by the engineer, a second-storey addition on an existing two-car garage in Riverview typically runs $60,000–$100,000 for a finished bonus room or loft space. This includes engineering, permits, floor framing, second-storey wall framing, new roof structure, roofing, insulation, drywall, electrical, windows, and stairs. If foundation work is required, add $10,000–$25,000 to that range.

If those numbers are close to or exceed what a new garage-with-loft would cost on your property, it's worth getting a quote for a full tear-down and rebuild — sometimes starting fresh is structurally cleaner and more cost-effective than retrofitting a structure that wasn't designed for two storeys.

The Professional Path Forward

This project requires, at minimum: a structural engineer for the assessment and stamped drawings, a building permit from Riverview, a general contractor experienced with structural additions, and a licensed electrician for the second-floor electrical work. If you're adding a bathroom above, a licensed plumber joins that list.

New Brunswick Garages can connect you with local contractors experienced in garage additions and second-storey builds in the Riverview and Greater Moncton area. You can also find structural engineers and general contractors through the New Brunswick Construction Network directory at newbrunswickconstructionnetwork.com. Start with the structural assessment — everything else flows from what that engineer tells you about your existing foundation.