This is a great attention getter about fireplaces and the need for proper inspection and maintenance. James Quarello is a home inspector from Connecticut and is relating to you a story from a recent home inspection and the 50 to 60 year old fireplace.
If the word 'parging' is new to you, it's another reason to read this post. Yearly inspection of your fireplace should be mandatory just like you tune-up your furnace every fall.
Everyone's gone at one time or another to the Fun House at the carnival. It's supposed to be a walk or ride through a scary chamber of horrors. The journey through is about as scary as a litter of kittens. About the only ones who get spooked are the littlest kids.
Yet there are real life situations that can be scary. Not a bogeyman jumping out of the dark and scaring the crap right out of you kind of scary, but a holy cow that could really turn into a bad situation with people getting hurt kind of scary.
A fireplace is not some thing that may conjure up nightmarish visions. On the contrary it is a place that has quite the opposite effect. A warm roaring fire in the middle of winter is a cozy and relaxing image.
But what if the fireplace is built incorrectly and in essence is an accident waiting to happen? That warm and cozy spot could be the start of a house fire.
Just above the fireplace is an area known as the smoke chamber. This is the transition from the fireplace to the flue. This is also an area that is often constructed wrong.
A masonry fireplace is obviously built from bricks and mortar. To narrow the smoke chamber to the flue size the bricks are "corbelled". This simply means that the bricks are hung partially over the bottom course to create an angle and decrease the size of the chamber going up. Often what is not done is the finishing of the smoke chamber by parge coating.
Parging is the smooth coating of the bricks with a special insulating refractory mortar (it is also required by building codes). The reason for parging is to fill any gaps in the masonry and provide a smooth transition for smoke. It also protects the bricks and mortar joints from the extreme heat of a fire which will open the joints over time. When a void in a mortar joint occurs it provides a path for heat, not necessarily flames, to combustibles around the fireplace and chimney.
Wood studs in the walls will become pyrolized over time from the heat. This is a physical change to the wood that lowers its ignition point from 450 º F - 500 º F down to 200° F - 225° F. Pyrolized wood once ignited can smolder for days until it finds an open area and thus an oxygen source. Once that occurs the result can be a full blown house fire.
The photo to the right is the inside of a smoke chamber from a 50 - 60 year old home I recently inspected. The smoke chamber has never been parged, even later when a good part of the entire chimney was rebuilt. This particular fireplace has certainly been used frequently. What may be difficult to see in the photo are the openings between the brick and mortar joints. Some of these openings were almost a quarter inch wide. This fireplace should not be used until it is repaired by a qualified chimney specialist.
This was truly a chamber of imaginable horrors.
James Quarello
NRSB #8SS0022
JRV Home Inspection Services, LLC
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