Can I convert my single-sided Ottawa fireplace into a double-sided one without major renovations?

Converting a single-sided masonry fireplace into a true double-sided fireplace without major structural work is unfortunately not realistic in most Ottawa homes. You would essentially need to rebuild the chimney core, firebox, and internal partition — which is itself a major renovation and can cost $8,000 to $20,000 or more depending on the chimney height and location.

Here's why conversion is so difficult: A single-sided fireplace has its firebox, damper, and smoke chamber built to draw air from one room only. Converting it to serve two rooms requires rebuilding the internal structure so both sides can independently access combustion air and exhaust into a shared chimney — or creating entirely separate flue passages. The masonry work must be done precisely to ensure proper draft, prevent smoke blowback, maintain structural integrity, and meet Ontario Building Code requirements. You cannot simply knock a hole through an existing fireplace and expect it to draw properly or safely on both sides.

What you can actually do instead:

The far more practical solution is adding a gas insert fireplace to the adjacent room on the other side of the fireplace wall. If your existing single-sided fireplace is on an interior wall shared with another room, you can often install a direct-vent gas fireplace on the opposite side without significant structural work — just a gas line run and venting. This gives you the appearance of a double-sided fireplace (or double-fireplaced space) with far less cost and disruption. A gas fireplace insert on the opposite side would run $2,500 to $5,500 installed, compared to $8,000 to $20,000+ for rebuilding your existing chimney. You'd have two independent, controlled heating appliances rather than one shared system.

Another option is installing a gas insert into your existing single-sided fireplace if you don't currently have one. Modern gas inserts can heat both rooms reasonably well depending on room size and layout, especially if the fireplace is centrally located. A quality gas insert runs $2,500 to $5,500 and provides 25,000 to 40,000 BTU of heat output — often enough to warm an adjacent room through an open doorway during Ottawa's shoulder seasons.

If your fireplace is on an exterior wall and a second fireplace on the other side would require creating an exterior chimney or penetrating the roof with a new vent, costs and complexity rise dramatically.

The critical question: Is the wall you want to open to interior or exterior? Is a second fireplace on that side structurally feasible, or would you need a new chimney? Once you answer those, you'll have a clearer picture of what's actually possible and affordable.

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• M.O.T. CONSTRUCTION INC.