Chimney Repairs
Many masonry chimneys have been in service for decades. We’ve looked at a few over a century old! Quite incredible that such basic materials such as clay, brick and mortar can have such a long life while containing high temperatures, acidic smoke and other combustion byproducts. We’d not expect any other appliance in or out of our home to last this long let alone do it with very little maintenance or repairs. This all assumes the fireplace and chimney was constructed properly in the first place.
Here are some common examples of defects that we find:
Chimney is constructed with a ‘wash’ instead of a crown. The wash does not have an overhang to protect the bricks and mortar from rain and leads to the top layers of bricks and their joints breaking down. The wash also is generally only constructed of mortar-easier to work with- and not gravel based concrete which is designed to withstand the elements, like a driveway.
Flue tiles do not have an expansion joint around them. When the clay flue gets hot it expands outward and upward. If the crown or wash material is poured right up to it, the concrete or mortar will crack from the stress. Cracks allow water to seep into them and eventually will start leaking into the fireplace itself. With our frequent freeze/thaw cycles in Michigan, any water that gets in there will likely freeze and create larger and more cracks, just like our roads:) If the crown is properly constructed and just has some cracks, our specialized waterproofing application can give it many more years of service.
Spalling bricks. Think of this as a delaminated brick. Typically, this is caused by water exposure but it could also be from a poorly manufactured batch. Either way, it will lead to a complete structural failure if left unrepaired.
Missing mortar joints between the flues. This allows smoke, or in the case of a chimney fire, fire, to go into areas of the chimney and home that are not built to contain them. This is usually the result of an incorrect mortar type being used. Flue joints require a different type of mortar than the rest of the fireplace construction and it is often easier for the original mason to just use one type. By the time anyone notices, it’s probably been 30 years! They can also degrade over time and use.
Cracked flues. This is very common to see after a chimney fire or any other rapid heating event. Even starting the fireplace with a few old pizza boxes can cause the flue to heat up too quickly. What happens is, the inside of the flue gets really hot-trying to expand- and the outside is still cold. Flue tiles are very heat resistant but also brittle and resistant to quick temperature changes. If you really want to geek out on this, look up “Young’s Modulus”.
Smoke chamber is corbeled. Think of the smoke chamber as a funnel for the smoke to go from the fireplace into the chimney. If the sides of the funnel have steps in them, how do you think the smoke will flow? Not very well, of course! This is a typical and too common shortcut done during the initial construction. The turbulence caused by the smoke flowing over the steps not only causes poor drafting but also allows creosote to build up in all the corners, which is very difficult and time consuming to remove. Sometimes it will even need a chemical treatment and multiple trips to completely remove.
This is by no means a complete list, just what we commonly see. The good news is, almost all of them have at least one if not multiple solutions.
- Cracks in an otherwise properly constructed crown can be waterproofed.
- A ‘wash’ can be removed and a proper crown constructed. A crown with no expansion joints can be removed and replaced.
- Missing mortar joints or cracks in the flue can be relined with stainless steel or have Heat Shield cerfractory sealant applied by our factory trained team. The correct solution will depend on the configuration of the chimney. Heat Shield video
- Smoke chambers can be ‘parged’ smooth
- For flue tile damage or a corbeled smoke chamber another option is to install a fireplace insert. These will have their own liner system and not use these parts of your fireplace and chimney. For a similar price to repairing your chimney you can have a whole new look, more efficient appliance and a much greater heat output. Check out our insert page!
