/ Field knowledge · IMC 903
A factory-built fireplace is a listed system, not a box in a wall.
Listed and labeled, installed per the listing, tested to UL 127. Hearth extensions follow the fireplace listing and, if listed, UL 1618. Unvented gas log heaters and gasketed doors only if that fireplace system is specifically listed for them. Distinct from IMC 805 factory-built chimneys. Daily Code Talk #169.
Packet: 903 PDF · ES. Source: DCT #169.
- 903.1: UL 127. The listing is installation criteria.
- 903.2: hearth readily distinguishable from the surrounding floor.
- 903.3 / 903.4: physical fit is not compatibility for logs or gasketed doors.
Aftermarket gasketed doors and unvented logs on a UL 127 box
Four accessories. Zero listed system.
What to send
Manufacturer and model, whether logs or doors are proposed, and the hearth detail.
If the appliance is already on the schedule and the path is not
Send the cut sheet, the fuel, and the occupancy. Masterbuild will say whether Chapter 9 still has no row — not whether the AHJ will accept a substitution.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
Masterbuild provides engineering services under a written scope. Not a fireplace design. Distinct from 805 chimneys. Confirm adopted 903. This is not legal advice.