22 Apr This Old Chimney
We buy and sell homes today with little to no thought as to the condition or suitability of chimneys and fireplaces for use. We often don’t have them inspected only to be surprised when problems arise or they fail subsequent inspections. Owners are angered they got stuck with an expensive problem and denied the enjoyment they were so looking forward to. Why is this?
Masonry chimneys have evolved over the years. This is due to a combination of learning what works and what doesn’t combined with improvements in technology and construction. The basic fireplace remains the same: enclose a fire on three sides and provide a pathway for the heat and smoke to escape in a direction and discharge of your choosing. Anyone who ever got campfire smoke in their eyes can appreciate this.
An open flame produces radiant heat- infrared energy directed line of sight. We feel this heat standing in front of a fireplace. However, the bricks lining the firebox absorb much of this energy then release it slowly into the room. There have been improvements in designs to get more heat out of an open-hearth fireplace but they will always be relatively inefficient heaters and very good at actually cooling rooms down.
The essential concept of a fireplace is to deliberately bring an open fire into a home. Think about it. That should sound crazy, right? I mean, you wouldn’t build a campfire in the middle of your living room would you? Of course not. Obviously there are things that must be done to make it reasonable free from risk of harm to do this. Notice I didn’t say “safe”. That’s a dangerous word because it’s an absolute term of nirvana that does not exist in this world. We can make things “saf-er” or reasonably free from risk of harm.
Ok, so what does this look like? Well, I could attempt to describe each detail of construction but someone has done it for me: The codes and standards. In our case, the International Residential Code and National Fire Protection Association standard 211 for Chimneys, Fireplaces, Vents and Solid Fuel-Burning Appliances are the primary references. There are others that may apply but these will get you most of what you need to know. These documents undergo a rigorous review and revision every 3 years. This ensures relevance and validity. We learn more each year, which brings me back to old chimneys. Those builders didn’t know what we know. We now have a body of evidence and scientific data to base decisions on. We have standards for what constitutes a hard fired brick suitable for this use and not indoor decoration. We have standards not only for the special high temperature non-water soluble cement used between flue tiles but also how to lay it. We have standards that preclude many of the architectural details you see on old chimneys because they caused damage such as retaining water instead of draining it.
There are some issues with old chimneys that have modern repair options to render them suitable for their original designed use, such as an open fireplace or heater flue. There are somethings we simply cannot engineer around, such as grossly undersized flues or not without very expensive repairs. In some respects, we can make chimneys and fireplaces much better inside and out. There are some challenges, such as converging roof valleys and nightmare water management issues that simply cannot be corrected without a major re-design and remodeling.
Chimney Cricket can state that after repairing and rebuilding chimneys in southeastern PA for over 30 years we can confidently state that virtually all the chimneys and fireplaces in this region were improperly built using inadequate materials and techniques and require extensive, expensive repairs. If you are to assume anything about the chimneys in this area it is safe to assume they have significant issues and should be inspected. We get it: chimneys and fireplaces aren’t the most exciting part of a home. Everyone wants that open concept glamour kitchen and master suite. However, before you sink a fortune into those improvements you should know what’s lurking in that chimney because the repair potential is high. Ignoring chimneys is a good way to add a decimal place to the price tag of the eventual repair.
Old chimneys and fireplaces have charm and may look quaint. Those old colonial walk-in fireplaces with the huge wooden beam lintel look cool. Those beams are charred on the backside, which is why colonials learned to put the cookfire in a separate outbuilding so only that structure burned down and not the house. I’m serious. We find charred wood everywhere in crazy places that make you shake your head. Every chimney in this area has wood in direct contact instead of the stated clearances to combustibles. Why would anyone put wood under the floor of the firebox? Why is the framing along with the lath & plaster touching the chimney? Why did they use wood forms under the hearth extension? Because they did not appreciate heat transfer and pyrolysis—the chemical reduction of a hydrocarbon by heat over time resulting in the conversion to charcoal, which has a much lower ignition temperature. Brick doesn’t burn but it is wonderful at conducting and storing heat. That’s why modern codes require certain clearances to combustibles in special places, certain wall thicknesses, etc. or an engineered solution.
A major problem is water management or the lack thereof. Most chimneys were improperly designed and constructed of very porous materials that don’t weather well. Chimneys are massive water storage systems. That water destroys chimneys that are improperly constructed and not maintained. Look at old historic chimneys. You’ll see the part above the roof looks different from the rest of the house. That’s because it has been repaired or rebuilt so many times. Improper materials, such as modern mortar, can ruin a chimney. Most modern repairs by untrained masons ruin chimneys.
We have engineered solutions for many of these problems but not all. Sometimes, like doctors, we have to give bad news. Sometimes the only thing a fireplace may be suitable for is flowers, candles or perhaps a Manhattan fireplace- a TV running a loop of a burning fireplace. We don’t like to break this kind of news to people but if you don’t want to inherit major problems before you buy and get stuck with expensive repair bills or heartache, have Chimney Cricket inspect your chimney on the front end so you know what you’re dealing with. Allow us to assist you in making an educated decision on your home.