Open-concept living is everywhere. Wider garage doors, panoramic windows, kitchens that flow into dining rooms without a wall in sight — these are the renovations Ontarians are asking for, and contractors are happy to deliver. But there is a structural consideration that rarely makes it into the conversation: what is that wall actually doing, and what happens when it’s gone?
In most cases, the answer to the first question is “more than you think.” And the answer to the second is “something has to take its place.”
Gravity Is Only Half the Story
When most people imagine how a house holds itself up, they picture the roof sitting on the walls, the walls sitting on the foundation. Weight pushing down, structure pushing back up. That’s gravity loading, and it’s intuitive.
What’s less intuitive is that a house also has to resist forces pushing sideways. Wind is the most obvious example — a strong gust against the side of your home is pushing horizontally on the entire face of the structure. But there’s also the subtler effect of earthquakes, which shake the ground beneath the foundation and send lateral forces up through the structure. Even in Ontario, which is not earthquake country in the way British Columbia is, seismic loads are a real design consideration, particularly in the Ottawa region, which sits near the Western Quebec Seismic Zone.
These horizontal forces have to be resisted somehow. A house that can handle its own weight but can’t resist lateral loads will rack — the walls lean, the floors shift, and in severe cases, the structure can collapse sideways. This is not a theoretical concern. It is why the prescriptive requirements in Part 9 of the Ontario Building Code include specific provisions for wall bracing.
How Wood-Frame Homes Resist Lateral Loads
In a conventional platform-frame house — the type that makes up the vast majority of single-family homes in Ontario — lateral resistance comes primarily from shear walls.
A shear wall is not a special wall. It’s any wall where the structural sheathing (typically OSB or plywood) is properly nailed to the studs and connected top and bottom to the floor and roof diaphragms. When a lateral load hits the building, the sheathing acts like a rigid membrane, distributing the force down through the studs and into the foundation. Think of it less like a column holding something up, and more like a card in a deck — stiff against being pushed sideways.
The key word is properly. The nailing pattern, the panel thickness, the connection to the foundation — all of these matter. But in a home that was built to code and hasn’t been modified, the shear walls are already there, quietly doing their job, hidden behind the drywall.
The problem is that they’re invisible. Homeowners don’t know they’re there. And so when someone decides to open up an exterior wall for a larger window, or remove an interior wall to connect two rooms, those shear walls get removed — or reduced — without anyone stopping to ask what that means for the building’s lateral resistance.
What Happens When You Remove a Shear Wall
Removing a shear wall does not remove the lateral load. Wind doesn’t care that you’ve renovated. What it does is eliminate one of the load paths — the route the lateral force was taking from the roof down to the foundation.
The load then has to find another route. If there are other shear walls nearby that have enough capacity to take the additional demand, the building may be fine. But in many renovation scenarios, especially in homes where multiple walls have been removed over the years, the remaining walls may be overloaded — more lateral force than they were designed to handle.
The consequences of an overloaded shear wall aren’t always immediately visible. Walls can rack gradually. You might notice doors that stick, cracks at window and door corners, or gaps between floors and walls. In more severe cases — or during a significant wind event — the structural consequences can be rapid and serious.
Interior walls can also contribute to lateral resistance, and this surprises many people. A long interior partition that runs the full depth of the house and is properly sheathed may be providing significant bracing perpendicular to the exterior walls. Remove it to open up the floor plan, and you may have eliminated lateral resistance in that direction entirely.
The Portal Frame Solution
So what happens when an opening is unavoidable? A client wants a wide garage door. A homeowner needs a picture window that spans most of an exterior wall. A contractor has already removed a bearing wall and now the engineer is being called in to sort things out. (It happens more than you’d think.)
This is where a portal frame comes in.
A portal frame is a structural system where a beam and two columns are connected rigidly at their joints — meaning the connections are designed to transfer not just vertical load, but bending moment. That moment resistance is what allows the frame to resist lateral forces in the plane of the opening, even without any sheathing across it. The frame acts like a rigid rectangle that resists being pushed into a parallelogram.
Recently, our office completed a design for a portal frame at a residential property in the Ottawa area. The owner wanted a wide opening in an exterior wall — the kind of opening that would have eliminated nearly all of the shear capacity in that wall line. A conventional shear wall solution wasn’t feasible at the desired opening width. The portal frame allowed us to restore the necessary lateral resistance in a compact assembly that fit within the existing wall depth.
Portal frames in residential construction typically involve a steel moment connection, or a heavily engineered wood connection, at the beam-column joints. They also require proper hold-downs at the base of the columns — mechanical anchors that connect the frame to the foundation and prevent the columns from lifting or sliding when the frame is resisting lateral load. Without the hold-downs, a portal frame is just a beam.
This is exactly the kind of detail that gets missed when a contractor frames an opening without engineering input. The beam goes in, the opening looks great, but the lateral load path is incomplete.
What Homeowners Should Know Before They Renovate
You do not need to be a structural engineer to ask the right questions. Before any wall comes out — interior or exterior — here are a few things worth considering:
- Is it an exterior wall? Exterior walls are almost always part of the lateral resistance system. Any modification to an exterior wall — particularly a wall running parallel to the dominant wind direction — warrants a structural review.
- How long is the wall, and how much sheathing does it have? Longer walls with continuous sheathing panels provide more shear capacity. A wall with a door or window already in it may have limited remaining capacity even before your renovation begins.
- Has the house been renovated before? If previous owners already removed walls or opened up sections of the exterior, the remaining lateral resistance may already be marginal. Each successive renovation compounds the risk.
- Are you in the Ottawa region? As noted, the Ottawa area has a meaningful seismic hazard, which means lateral design requirements here are not trivial. Homes that were built before modern seismic provisions were in place may already have limited lateral resistance.
The best time to involve a structural engineer is before the walls come down, not after. A structural review at the planning stage is straightforward. A structural review after the contractor has already framed the opening is more complicated, more expensive, and occasionally disheartening.
A Note on the Building Code
Part 9 of the Ontario Building Code provides prescriptive requirements for bracing in wood-frame construction. These are the rules that allow a home to be built without a structural engineer designing every wall — they’re essentially pre-engineered solutions for conventional construction.
The problem is that those prescriptive requirements assume the home is being built, or renovated, in accordance with the code. The moment you start removing wall segments, enlarging openings, or changing the configuration of the structure in ways that deviate from the prescriptive tables, you’re outside the scope of the prescriptive solution. At that point, an engineered design is required — not as a formality, but because the tables no longer apply.
Many homeowners and contractors don’t realize this. They assume that as long as the renovation looks reasonable and nothing falls down immediately, the building code has been met. That assumption is not always correct.
The Bottom Line
Lateral stability is one of those things that’s easy to overlook because it’s invisible and because the consequences of ignoring it can be slow to manifest. But it is a fundamental part of how your home functions as a structure, and it deserves the same attention as any other structural element.
If you’re planning a renovation that involves removing or modifying walls — especially exterior walls or long interior partitions — reach out to a structural engineer early in the process. It’s a conversation that can save significant time, cost, and headache down the road.