IMC 801.12 and 801.13 are small-dimension requirements with real field consequences: where the connector enters the chimney, and whether the chimney can actually be inspected and cleaned after construction. Both are about serviceability - and both are easy to lose behind a generic "connect to existing chimney" note.
Plain-English Highlights
IMC 801.12 (Chimney Entrance): connectors must enter the chimney flue at a point not less than 12 inches above the lowest portion of the interior of the chimney flue. That 12-inch separation keeps the connector from discharging directly into the bottom of the flue where debris, condensate, ash, or soot may collect. For plan review, the connector elevation matters - the drawings should show the appliance connector entering the chimney at a compliant height.
IMC 801.13 (Cleanouts): masonry chimney flues must have a cleanout opening with a minimum height of 6 inches, with the upper edge of the opening at least 6 inches below the lowest chimney inlet opening, and a tight-fitting, noncombustible cover. Exception: a cleanout is not required for chimney flues serving masonry fireplaces when access is provided through the fireplace opening.
Permit Proof Chain
Appliance connector routing -> chimney entrance elevation shown (not less than 12 inches above the lowest interior flue portion) -> cleanout located below the lowest inlet (6-inch minimum height, upper edge at least 6 inches below the lowest inlet opening) -> tight-fitting noncombustible cover -> access preserved after finishes and casework -> inspection and maintenance path verified.
Where To Show It
M-001: chimney connector and cleanout notes. M-101: appliance location and chimney connection point. M-501: connector entrance, cleanout, cover, liner, and access details. M-601: appliance schedule with chimney / venting basis. A/LS sheets: chimney, fireplace, shaft, wall, and rated assembly coordination.
**Do** - Show the chimney connector entrance elevation. - Provide the required 12-inch separation above the lowest interior flue portion. - Show masonry chimney cleanout size, location, and cover. - Confirm cleanout access is maintained after construction.
**Do Not** - Use "connect to existing chimney" without showing the connection point. - Hide cleanouts behind finishes, equipment, or casework. - Omit the noncombustible tight-fitting cleanout cover. - Assume fireplace access satisfies cleanout requirements unless the exception actually applies.
Masterbuild QA Lens
The vertical relationship IS the review: connector inlet above, cleanout below, both accessible. A chimney detail that doesn't show elevations can't be reviewed against 801.12 or 801.13 - it can only be assumed, and assumptions are what reinspections are made of.
Drawing / Submittal Check
For each appliance connected to a chimney, find two things on the details: the connector entrance elevation, and the cleanout with its size, location, and cover. If either is missing - or the connection is covered by a bare "connect to existing" note - the submittal is incomplete, not field-resolvable.
Common Review Risk
Existing-building reuse is where these sections bite: an old chimney reused for a new appliance with no entrance elevation shown, a cleanout that is missing, blocked, undersized, or - most common - concealed behind new finishes, equipment, or casework once construction ends. That leads to soot buildup, blocked flues, poor draft, corrosion, combustion-product spillage, and failed inspections.
When To Escalate
Escalate existing chimney reuse without a documented condition and liner basis, any configuration where the cleanout cannot be located below the lowest inlet opening, and fireplace-exception claims where real access through the fireplace opening is doubtful.
Field Tip
When reviewing a masonry chimney detail, check the vertical relationship: connector inlet above, cleanout below, and both accessible. If that relationship is not shown, the chimney detail is incomplete.