What is a prefabricated (prefab) fireplace?

Prefabricated fireplaces, or prefabs for short, are manufactured metal fireplaces that are built offsite and installed by a chimney technician or contractor, usually in new homes as they are being constructed. 

In Vermont and New Hampshire these became very popular in ski areas due to the quick installation time and low cost as compared to traditional masonry fireplaces. Many were installed during the 1960’s-1980’s.

All About Prefabricated Fireplaces

Above is a prefabricated fireplace installed prior to the hearth, finish and façade work being completed.

All About Prefabricated Fireplaces

What does the recommended use of a prefabricated fireplace look like?

Prefabricated fireplaces are designed to be decorative appliances; they are not meant to heat your home. They are designed for small ambient fires burned for short periods of time. It is all too common to see prefabricated fireplaces loaded to the brim with wood and becoming damaged due to this.

What is the lifespan of a prefab fireplace?

Like most household appliances, the lifespan of a prefabricated fireplace is approximately 10-15 years. Obviously, if the fireplace is abused and not maintained properly, or sustains a chimney fire, that will reduce its lifespan. On the other end of the spectrum, there are fireplaces that see very little use and that have lasted well over the normal lifespan.

What are some common safety concerns or deficiencies found with Prefabricated fireplaces?

There are two categories that I would put under safety concerns when it comes to prefab fireplaces.

1. Deterioration or damage from use or normal wear and tear

One of the most obvious places to see damage in prefabricated fireplaces are cracked refractory panels, which mimic the look of bricks inside the fireplace. These can crack or deteriorate over time. Also, in the metal chimney flue, we sometimes find that the chimney liner becomes damaged or warped due to the high heat or the fires in the fireplace. A chimney fire can often exacerbate this issue. Finally, prefab fireplaces commonly rust from being exposed to leaks for years or, for those on the seacoast, from salt air eroding the metal components.

All About Prefabricated Fireplaces

In the above picture you will see cracked refractory panels in the rear wall of a prefabricated fireplace. These panels will need replacement (If they are still produced by the manufacturer).

All About Prefabricated Fireplaces

The picture above was taken inside a prefabricated Fireplace chimney in Stowe Vermont.  Notice the warped sections of chimney pipe.

2. Improper installation or repairs.

Prefab fireplaces were often installed hastily, like many of the ski homes they are built in. It’s safe to say that the installation instructions were not often followed. The fireplace and chimneys are enclosed in a wooden chase. All to often we find that the framing of the wooden chase is built too close to the chimney and fireplace. The framing can get so hot, it can ignite, causing a fire.  

When constructing the hearth extension or area in front of the fireplace, the manufacturer’s instructions will usually require a certain R-value of material to protect the floor underneath. Yet, we often find just a single layer of tile over a wooden subfloor. That single layer of tile is inadequate protection from heat radiating on the subfloor. Finally, while inspecting the attic areas of these homes, we often find that insulation (typically blown-in insulation) is touching the chimney pipe as it runs through the attic, which can combust.

All About Prefabricated Fireplaces

During an attic inspection this picture was taken documenting wood framing touching the prefabricated fireplaces’ chimney pipe. A 2” minimum air space to combustible material is required by this manufacturer.

All About Prefabricated Fireplaces

This picture was taken in the same attic showing combustible insulation touching the chimney pipe as well.

Can a prefabricated fireplace be repaired?

If a part of a prefab fireplace becomes damaged, it can be replaced; however, it is important to know that all the components of a prefab fireplace are UL-listed and tested as one system. This means the parts are not interchangeable between different manufacturers or models. Any part used to repair these fireplaces must be the same make and model as the fireplace in need of repair. But many parts are no longer made. If the fireplace is over 20 years old there is a good chance the parts are no longer available. Unfortunately, if the parts are no longer available, the chimney and fireplace would need to be completely replaced. 

Furthermore, the prefab fireplace should not be modified in any way from its UL Listing. The wrong components, such as a chimney pipe, rain caps, glass doors, or log grates, can cause the overheating of the fireplace and nearby combustible material, which could lead to a house fire.

All About Prefabricated Fireplaces

Above is a picture taken up inside a chimney chase. The chimney had been removed after the wood framing touching the chimney pipe ignited and caused a house fire.

Can I install a propane or wood burning insert in this type of fireplace?

The answer is most likely no, you cannot. This type of fireplace was not designed to operate with a wood or propane insert in them. Just like it’s dangerous to use parts that are not made by the same manufacturer, a wood burning insert could cause the fireplace or chimney to overheat and catch nearby combustibles on fire.

There may be some rare cases where the manufacturer of the fireplace specifically says in its manual that it is acceptable to do so, but we do not typically see this.

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