Zero-Clearance Firebox Installation

A factory-built, zero-clearance firebox is the smart way to add a real wood- or gas-burning fireplace to a framed wall — but it's only as good as the installation. These are UL-listed appliances with exact clearance, chase, and venting requirements, and the difference between a safe, efficient install and a fire-hazard one is entirely in the craftsmanship. Prime Chimney Experts installs zero-clearance fireboxes strictly to their listing.

The phrase 'zero clearance' is misleading and dangerous if taken literally. Every listed firebox specifies precise clearances to framing, a required chase construction, and a specific Class-A chimney system — and those numbers are not suggestions. We frame the chase to the manufacturer's dimensions, set the firebox so its listed clearances to combustibles are held exactly, and run the matching Class-A insulated chimney straight up with correct support, firestops at each floor, and a proper roof penetration. Mixing brands of pipe, fudging a clearance, or skipping a firestop is how a 'code' install becomes a slow-cook fire risk.

Draft and combustion air get the same discipline. We run the chimney to the required height above the roof for the 3-2-10 clearance rule so embers clear the roof safely, with the overall flue height sized for a clean draw, and where the home is tight or code requires it, we duct outside combustion air to the unit so it doesn't pull makeup air — and smoke — from the room. On gas models, the connection is made and leak-tested. The chase, cricket, and termination are built like the rest of the home: a back-side roof cricket so water sheds around the chimney, every penetration flashed, and the chase capped with a sloped stainless cover and an appropriate cap or shroud.

Inside, the firebox is set plumb and the surround is detailed to your design with the listed non-combustible clearances around the opening honored to the inch. Mounting a flat-screen above? We install a proper mantel/heat deflector so the listing — and your TV — are respected. A zero-clearance install is typically a few-day project; we leave you a documentation package with clearance photos, the gas test where applicable, and the termination detail, and we pull the permit and schedule the inspection.