/ Field knowledge · IMC 803.10.1–803.10.5
Four checks. Missing one is not reviewable.
Four field checks on one connector: independent support, horizontal length not more than 75% of the chimney or vent height, stop at the inner face of the liner (do not project into the flue), and a continuous rise of at least 1/4 inch per foot (2%). Missing any one of those at a transition is not fully reviewable.
Educational 2024 International Mechanical Code (IMC) 803.10.1–803.10.3 and 803.10.5 from Daily Code Talk. Confirm the adopted edition. Distinct from wall pass-through (803.10.4) and clearance (803.10.6). This is not a connector design. Daily Code Talk example: a 20-foot-high chimney allows a maximum 15-foot horizontal single-wall connector.
- 803.10.1: adequately supported; joints secured by sheet metal screws, rivets, or other approved means. Do not hang the connector on the appliance collar or the chimney opening.
- 803.10.2: maximum horizontal length of a single-wall connector is 75% of the chimney or vent height. Long horizontal runs increase resistance and can reduce draft. Put the height used for that check on the same sheet as the run.
- 803.10.3: extend to the inner face of the liner, not beyond it. Projecting into the flue restricts flow and collects deposits. Masonry: connector cemented to the masonry in an approved manner; removable thimbles permanently cemented with high-temperature cement.
- 803.10.5: minimum pitch 1/4 inch per foot or 2% slope, rising continuously toward the chimney or vent. Flat or downhill runs are the miss.
On the set: support locations, joint fastening, chimney/vent height for the 75% check, liner-connection depth, and pitch — on the same detail, not scattered notes. Trace the connector in section.
A horizontal run with no chimney height on the sheet
The reviewer cannot verify 75% without a building section that may not even be in the mechanical set. Sagging, joint separation, lost slope, and a pipe poked into the flue are the usual field outcomes.
Source: Daily Code Talk — IMC 803.10.1–803.10.5 · tool: Geometry screen · pass-through: 803.10.4 · dampers: 803.5–803.7.
What to send
Connector route in section, chimney or vent height, and whether the pipe is single-wall. Photos of sag, slope, and how it enters the chimney.
If the connector sags, runs long, or pokes into the flue
Send the section. Masterbuild will say which of the four checks still has no evidence.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
Masterbuild provides engineering services under a written scope. Nothing on this page is project-specific engineering advice, a code interpretation for your project, or a representation about permit approval. Confirm the adopted edition. The 75% length rule, 20-ft / 15-ft example, and 1/4 in. per ft pitch are 2024 IMC 803.10 education from Daily Code Talk — not a connector design. This page is not legal advice.