What is the cost of a timber frame sunroom addition in Ottawa?

A timber frame sunroom adds an exposed post-and-beam structure and a lot of natural light to a house. It usually costs more than a conventional stick-framed sunroom, because of the heavy timber, the joinery and the glazing, but many people choose it for the look and the durability.

As broad perspective, a fully finished four-season timber frame sunroom of around 200 square feet can range from roughly $100,000 to $160,000, and a three-season version usually costs less. Treat those as perspective, not a quote.

Three-season or four-season. A three-season room isn't built to be heated through the winter. A four-season room is heated living space, so it is treated as an addition for energy efficiency and must meet a compliance package or the addition table under SB-12. That usually means insulated roof panels between or over the timber rafters, high-performance glazing and a heat source, such as an extension of your existing system or a ductless heat pump.

The frame. The timber frame is a significant part of the cost. Douglas fir is a common species, and eastern white cedar and white pine are local alternatives. Frames often use traditional mortise-and-tenon joints secured with wooden pegs, and they are usually cut off-site by a timber frame shop and raised on your foundation in a short time. Ask for the frame package as a separate line so you can compare shops.

Foundation. Options include a full frost wall, helical piles or a frost-protected shallow foundation. Which one works depends on the soil and on whether the room will be heated, and your designer or engineer will confirm it. Conventional footings on clay or poorly defined soils must be at least 1.2 m deep and not shallower than the depth of frost penetration.

Permit. A four-season sunroom built as an addition needs a building permit; the City's permit list names one- and two-storey additions. Under the 2026 schedule the fee is $12.75 per $1,000 of construction value (minimum $117), so a $130,000 project works out to about $1,658, though the City confirms the valuation.

Glazing. A timber frame sunroom often has floor-to-ceiling glass or large fixed windows between the timber bays. For a heated room, triple-pane, low-E, gas-filled units make it far more comfortable in winter. Glass is a major cost driver, so ask for glazing as its own line.

You can browse addition contractors with timber frame and sunroom experience in the Ottawa Construction Network directory at justynrookcontracting.com and ask for site-specific, itemized quotes.

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Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:

• 613Bins
• JC Carpentry
• JMY Renovations
• ARTEXPRO Tile & Finishes
• MAK Construction and Development Inc