How is a Calgary fireplace chase framed?

A fireplace chase is a framed enclosure — typically built from wood or steel stud framing — that houses the venting system for a gas or wood-burning fireplace, running from the firebox level up through the ceiling and roof of the home.

In Calgary new construction and renovation projects, chases are most commonly built for direct-vent gas fireplaces and wood stoves or inserts where the vent pipe needs to travel vertically before exiting the roof, or where a horizontal vent run needs to be concealed within the wall assembly. Understanding how a chase is framed helps you plan your fireplace project, communicate with your contractor, and understand what's behind the finished drywall and stone surround.

The Basic Framing Structure

A fireplace chase is framed much like an interior wall, but built as a three-dimensional box. The framer builds a floor platform (the chase base), four vertical stud walls, and a top plate that ties into the ceiling and roof framing above. Standard dimensional lumber — typically 2×6 or 2×8 — is used rather than 2×4 because the vent pipe running through the chase requires specific clearance to combustibles. The Alberta Building Code mandates minimum clearances between the vent pipe and any combustible framing material, and those clearances vary by vent type. A direct-vent coaxial pipe (the double-wall pipe used on sealed-combustion gas fireplaces) typically requires 1 inch of clearance to combustibles. A Class A insulated chimney pipe for a wood stove requires 2 inches of clearance to combustibles — which is why wood stove chases tend to be larger.

The chase is framed plumb and square, then fire-blocked at each floor level with solid lumber or fire-rated material. Fire blocking is not optional — the Alberta Building Code requires it to prevent a chase from acting as a concealed vertical pathway that allows fire to travel rapidly between floors. Inspectors check for fire blocking during the framing inspection.

Interior vs. Exterior Chase Placement

This is one of the most important decisions in Calgary's climate. An interior chase — built inside the home's thermal envelope — keeps the vent pipe warm, which improves draft performance and reduces condensation inside the flue. An exterior chase — built on the outside of the home's exterior wall — is more common in production homes because it's simpler to frame and doesn't consume interior floor space, but it creates a cold column of air that can cause draft problems and condensation issues during Calgary's -25°C to -35°C cold snaps. If you're building a new home or addition with a wood-burning fireplace or stove, an interior chase is the better long-term choice for Calgary's climate.

Clearances, Finishing, and the Surround

Once the chase framing is complete and inspected, it's sheathed in drywall — typically 5/8" Type X fire-rated drywall on the interior faces of the chase. The firebox opening is framed with a non-combustible header, and the face of the chase that faces the room becomes the canvas for your mantel and surround. Combustible mantels and trim must maintain minimum clearances from the firebox opening as specified in the Alberta Building Code and the fireplace manufacturer's installation manual — typically 6 to 12 inches depending on projection depth. Your installer will confirm the exact clearances for your specific unit.

What Requires a Professional

All gas fireplace installations — including the chase framing coordination, vent pipe installation, and gas line rough-in — require a gas permit from the City of Calgary and inspection by a Safety Codes Officer. The framing itself can be done by a general carpenter, but the vent pipe installation and gas connection must be done by a licensed gas fitter. For wood stoves, a WETT-certified installer is required, and a building permit is needed for any new roof penetration.

Need help finding a fireplace installer who can manage the full scope — framing coordination, venting, gas fitting, and finishing? Calgary Fireplaces can match you with local contractors through the Calgary Construction Network. Browse fireplace installers at calgaryconstructionnetwork.com/directory?trade=fireplaces.