Called by many different names (pre-fab, factory-built or zero-clearance fireplace), these manufactured fireplaces are factory constructed and installed in a building, as opposed to masonry fireplaces, which are built on-site.
While masonry fireplaces have strict rules governing the amount of clearance needed between the firebox opening and any flammable materials, pre-fab fireplace clearance requirements are dictated by the manufacturer’s specifications. These requirements can vary between manufacturers, and can be difficult to determine without having access to the installation instruction manual.
Home inspectors will typically include language like this in their inspection reports, if they are concerned that flammable materials may be too close to a pre-fab fireplace:
Hearth extensions, flammable mantles and trim on factory-built fireplaces must be installed according to manufacturer’s instructions. While the inspector does not have access to the manufacturer’s specifications, it appears that the clearances may not be an adequate distance from the front/sides of the firebox. Recommend consulting with a qualified tradesperson to verify proper installation according to manufacturer’s instructions and correct as needed.
Always follow the manufacturer’s specifications when it comes to installing and operating a fireplace. Your family’s life may depend on it.