Parge and smooth a corbeled smoke chamber to meet NFPA 211 smoke chamber requirements

Steps

1. Inspect the smoke chamber (typically via Level II access/camera) to determine whether the corbeled masonry surface is rough/stepped enough to impede smoke flow or create a codeable deficiency under NFPA 211's smoke chamber provisions
2. Confirm the smoke chamber shape and height meet the general geometry requirements referenced in NFPA 211 before doing surface work, since parging does not correct an incorrectly shaped or oversized chamber
3. Clean loose mortar, soot, and debris from the corbeled surface to provide a sound substrate for parging material
4. Apply a high-temperature refractory parging/insulating mix rated for smoke chamber use, building up over the corbeled steps to create a smooth, continuous surface that promotes laminar smoke flow toward the flue
5. Cure the parging material per the product manufacturer's instructions before returning the fireplace to use
6. Re-inspect (visually or via camera) to confirm the finished surface is smooth and free of gaps before closing out the job