Your prefab fireplace, repaired to its manual in East Park

Glass doors on a factory-built fireplace

Glass doors on a factory-built fireplace have to suit that fireplace. Section R1004.5 of the residential code says a gasketed fireplace door shall not be installed on a factory-built fireplace unless the fireplace system has been specifically tested, listed and labeled for that use under UL 127.

One maker offers its own door models for each size of fireplace. Before recommending any door repair or replacement, we identify what the listing allows, since a door that fits the opening may still be a door the fireplace was never tested with.

The chimney is part of the fireplace's listing

A factory-built fireplace is tested with a specific chimney. Section R1005.4 says chimneys for use with factory-built fireplaces shall comply with UL 127, the same standard as the fireplace, and R1005.1 has factory-built chimneys listed and labeled, then installed and finished at the top as their maker directs.

That makes the metal chimney a matched part of the system. Repairs to pipe sections, supports or the top of the chimney use the components the fireplace's manual names.

What may touch the face of the fireplace

One maker's instructions allow combustible materials such as wallboard and plywood to meet the sides and top of the fireplace face, provided they stay off the face itself. Brick, glass, tile or other noncombustible materials may overlap the face if they leave louvers and other openings clear.

The same manual calls for noncombustible mortar or adhesive when a noncombustible facing overlaps the face. Refacing jobs that ignored those rules can cause trouble, and we check them whenever a prefab repair brings us to the surround.

• Wallboard to the sides and top, never over the face
• Noncombustible facing may overlap
• Louvers and openings left clear
• Noncombustible mortar or adhesive only

Louvers and air slots stay open

Heat-circulating factory-built fireplaces move room air through channels around the firebox, drawing it in and sending it back through louvers or slots on the face. Those openings are part of the tested design.

Paint, facing material and furniture sometimes close them off. We check that every louver is clear and that nothing has been added in front of the openings the model depends on.

• Paint over the slots
• Facing material across the openings
• Furniture pushed against the grilles