Common Hidden Issues with Fireplace Construction
At Chimney Savers we perform thousands of fireplace inspections and cleanings each year. During these inspections, most homeowners envision us checking the damper area, chimney top, and chimney liner.
But many don’t know that our inspection services include, when possible, verifying if the fireplace was constructed properly. We have found that many fireplaces—even those built recently—have some common improper construction techniques. Here are some of the common issues we find.
Above is a diagram of a code complying fireplace. Notice the clearance required to the backwall of the fireplace and no combustibles allow underneath the hearth and hearth extension.
Wood below hearth and hearth extension
It’s hard to imagine that plywood would be installed below the hearth and hearth extension, but believe it or not, we find that more than half of the fireplaces we inspect have this safety concern. Usually when a fireplace is built, a block or concrete foundation is built in the basement of the house.
When the mason reaches the first-floor level, a plywood form is laid down to support a slab of concrete that the hearth and hearth extension of the fireplace are built on. This plywood form is often never removed.
This wood is now exposed to the heat radiating down from a fire in your fireplace. Over time this wood dries out, eventually to a point where it can combust, which can lead to the igniting wood framing in the house.
Above is a picture taken below the hearth of a fireplace in Norwich Vermont. Notice the burnt wood found left during original construction
Above is a close up picture of burnt wood found below a fireplace in Ludlow Vermont.
No airspace behind and on sides of fireplace
The back of the fireplace firebox is exposed to a large amount of heat. The layer of bricks you see in the back of your fireplace is just the first level of protection. Behind those bricks is another layer of concrete blocks or bricks. Because masonry radiates heat, this backwall of bricks should not have wood framing touching it.
In fact, according to the National Fire Protection Agency, there should be 4 inches of airspace between the outer layer of masonry and any combustible material. And yet, it is extremely common to see a framed wall touching the back of the fireplace, with zero inches of airspace. Like with the plywood situation just discussed, over time this wood dries out, greatly increasing the risk of combustion and framing in the house catching on fire.
Above is picture from a house fire which originated behind a fireplace. The required airspace behind the fireplace was not kept. During a fire the framing got so hot it ignited causing a house fire.
While not a safety concern, most modern fireplaces are not designed to throw heat into the room. In fact, most fireplaces have what is called a “net heat loss.” This means when you use the fireplace, heated air from your room goes up the chimney and doesn’t make the room any warmer.
So how are all these problems solved?
Sometimes the chimney and house construction make the removal of these combustibles possible. But these cases are rare and often involve large renovations inside the house. An alternative to this is Chimney Savers can install an innovative fireplace restoration product called an Ahren-Fire Kit, made in the U.S.A., which eliminates these clearance concerns and provides more efficiency from your fireplace.
What is an Ahren-Fire system?
The Ahren-Fire system is an all-in-one fireplace system that can restore and improve your fireside experience, without requiring you to do major renovations or completely rebuild your chimney and fireplace. The system was designed to eliminate the need for clearance to combustible framing, improve fireplace efficiency and performance, and to provide more heat and a cleaner, more complete burning of fuel.
Above are the components that make up an Ahren-Fire fireplace.
Will this change the look of my fireplace?
Yes. Unfortunately, the extremely insulated panels that make up the Ahren-Fire system do look different from a traditional fireplace. We have provided pictures below so you can get a better idea of what you could expect this system to look like.
Above is a slide show of Ahren Fire fireplaces which we have installed.
Paul Bianco is the General Manager of Chimney Savers, a family owned and operated chimney cleaning and repair company servicing Vermont & New Hampshire since 1989. With 12 years of experience in the chimney business, Paul has extensive knowledge in all things chimney.