Our 1950s Ottawa bungalow has single-wythe brick walls, what's the best way to add sound insulation inside?

Single-wythe brick walls are common in Ottawa's 1940s and 1950s bungalow stock — you will find them throughout Alta Vista, Carlington, Westboro, and older parts of Nepean. These walls are typically just one brick thick (about 4 inches) with minimal or no insulation behind the interior finish, which means they offer surprisingly little resistance to exterior noise despite feeling solid. The good news is that you can dramatically improve their acoustic performance from the inside without disturbing the exterior brick.
The Interior Build-Out Approach
The most effective method is to build a completely decoupled interior wall in front of the existing brick. Frame a new 2x4 stud wall leaving a one-inch air gap between the new studs and the brick surface — this air gap is critical because it breaks the direct vibration path from the brick to your interior drywall. Fill the stud cavities with Roxul Safe'n'Sound acoustic mineral wool ($1.20–$1.80 per square foot), then attach sound isolation clips such as RSIC-1 ($4–$7 each) with hat channel to the studs, and finally hang two layers of 5/8-inch Type X drywall with Green Glue compound ($15–$22 per tube) between them. Seal every edge, outlet, and penetration with acoustic caulk. This assembly can achieve STC 55 to 60, which is a dramatic improvement over the bare brick wall's typical STC 35 to 40.
With 1950s Ottawa bungalows, there are a few specific challenges your contractor needs to address. First, single-wythe brick is the structural wall and weather barrier combined, so you cannot alter it or attach anything heavy to it without understanding the load path. The new interior wall should be freestanding on the floor, not mechanically fastened to the brick — this also improves acoustic decoupling. Second, these older walls often have no vapour barrier, and in Ottawa's climate where winter temperatures regularly hit minus twenty-five to minus thirty, adding insulation without proper vapour management can cause condensation on the cold brick surface. Your contractor should install a 6-mil poly vapour barrier on the warm side of the new insulation to prevent moisture problems.
If you are in a Heritage Conservation District — parts of Westboro and some older neighbourhoods have heritage overlays — the interior approach is actually ideal because it leaves the exterior brick completely untouched. No heritage approvals needed for interior-only work, and typically no building permit is required unless you are altering structural elements or fire-rated assemblies. However, if you are adding or moving electrical outlets in the new wall, you will need a licensed electrician to handle those penetrations and seal them with acoustic putty pads ($3–$6 each).
Cost for this type of interior build-out in Ottawa runs approximately $18–$28 per square foot installed, depending on whether you use isolation clips (recommended) or resilient channel (budget option). For a typical 10-foot by 8-foot exterior wall, that works out to roughly $1,400–$2,200. You will lose about 4.5 to 5 inches of room depth per wall, which is a real consideration in a compact 1950s bungalow. Some homeowners choose to treat only the walls facing the noisiest exposure — often the street-facing wall — to balance cost against space loss.
A project like this benefits enormously from a professional site assessment, because every 1950s bungalow has its quirks — plumbing stacks in walls, original knob-and-tube wiring, or plaster-on-brick finishes that change the approach. Reach out through Sound IQ for more guidance, or browse the Ottawa Contractor Directory to find a soundproofing professional who understands these vintage Ottawa homes.Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:Luxe Painting and Renovations JC CarpentryFloor-2-Wall IncNic’s D.U.C.T Works IncDemontigny CarpentryView all contractors →