What's the best way to seal the perimeter of an older Ottawa window that has settled and has gaps?

The best approach for sealing a settled window with perimeter gaps is a layered strategy: acoustic caulk for small gaps, backer rod plus caulk for larger gaps, and spray-foam-plus-caulk for the rough opening behind the trim. Older Ottawa homes — particularly those in the Glebe, Old Ottawa South, New Edinburgh, and Centretown built before the 1960s — commonly develop window gaps as the wood framing dries, shrinks, and shifts over decades of Ottawa's punishing freeze-thaw cycles. These gaps are simultaneously sound leaks, air leaks, and energy drains, so sealing them properly pays dividends on all three fronts.Start with the visible gap between the window frame and the interior trim or wall finish. For gaps up to about 6 mm (1/4 inch), apply a bead of acoustic caulk such as Tremco Acoustical Sealant or equivalent at $8 to $15 per tube. Acoustic caulk remains permanently flexible, which is critical — standard silicone or latex caulk hardens over time and cracks open again as the building continues to move seasonally. One tube covers roughly 8 to 10 linear metres in a thin bead. For gaps between 6 mm and 12 mm, press in a closed-cell foam backer rod ($5 to $10 for a 6-metre roll) first, then apply caulk over it. The backer rod gives the caulk something to bridge against and prevents it from sinking into the cavity.Addressing the Hidden Gap Behind the TrimThe most significant sound and air leak in a settled window is usually behind the interior trim casing, in the rough opening between the window frame and the structural framing. Carefully remove the interior trim (pry gently with a flat bar and putty knife to avoid damaging plaster or drywall) and you will likely find the original insulation — if any — has compressed, fallen away, or was never installed. In many pre-1970s Ottawa homes, this gap was stuffed with fibreglass or newspaper, neither of which provides an air seal.Fill this rough opening gap with low-expansion spray foam designed for windows and doors (labelled "minimal expanding" or "window and door" — never use standard high-expansion foam, which can bow the window frame and prevent it from operating). Products like Great Stuff Window & Door cost about $8 to $12 per can and one can handles three to four average windows. Apply in thin beads no more than half the gap depth, allow to expand and cure for 24 hours, then trim flush. Over the cured foam, apply a bead of acoustic caulk to create a complete air and sound seal before reinstalling the trim.For the exterior perimeter, inspect the caulk joint between the window frame (or brick moulding) and the exterior wall finish. Ottawa's UV exposure and temperature cycling from -30°C to +35°C degrades exterior caulk faster than in milder climates — expect to recaulk every 5 to 8 years. Use a high-quality polyurethane or hybrid sealant rated for exterior use and paintable if needed. Remove all old cracked caulk before applying new material — layering new over old is a temporary fix at best.If the window has settled to the point where the sash no longer sits square in the frame — you can see daylight through the gap or the lock no longer engages properly — sealing alone will not fully solve the problem. The window may need to be re-shimmed and re-levelled in its rough opening ($200 to $500 per window by a carpenter) or, if the frame itself is rotted or severely warped, replaced entirely ($500 to $1,500 per window installed for a standard double-hung). For heritage properties in Ottawa's Heritage Conservation Districts, replacement windows may need to match the original profiles — check with the City of Ottawa heritage planning office before proceeding.Properly sealing settled windows is one of the highest-value improvements for both noise reduction and energy savings in older Ottawa homes. For a whole-house approach or windows with significant structural issues, consulting a professional ensures the work is done correctly and any building code or heritage requirements are met. The Ottawa Contractor Directory at justynrookcontracting.com/directory lists contractors experienced with both soundproofing and heritage window restoration in the Ottawa area.Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:Reno's by Daniel FrauwallnerRenoMotion Inc.Estra DesignARTEXPRO Tile & FinishesScott Smirle (Smirle Elite Contracting)View all contractors →