Before a chimney gets built, one of the key decisions to make involves the type of construction material.
Chief among these is the chimney brick. The type of chimney brick used for chimney construction is quite different when compared to those for building construction.
Consider the fact that chimneys are built to expel hot gases generated from combustion. At the same time, such chimneys supply air to sustain combustive action.
Now, due to ongoing combustion within the chimney system (fireplace), high temperatures are generated.
Standard issue masonry bricks won’t fit the bill. In other words, they aren’t quite suitable for chimney construction due to their low-temperature resistance.
Bricks used need to be heat resistant to qualify as building materials for chimney construction.
How Much Heat Do Chimney Bricks Need to Withstand?
One of the things we’ll need to clarify before proceeding further is the amount or degree of heat chimney bricks need to withstand.
Fire bricks used for chimney construction are engineered to withstand temperatures as high as 3000 degrees F.
Asides from the bricks used for building a chimney, the type of mortar used is equally important. If a chimney brick is designed to withstand temperatures as high as 3000 degrees F, then the mortar must also be heat resistant.
Specially formulated high-temperature cement is available for such purposes. This, added to heat-resistant chimney bricks will build the perfect chimney system.
Basic Criteria For Choosing Chimney Bricks
Based on the functional design of chimneys, chimney bricks should be carefully chosen. There are basically three criteria a chimney must possess.
These include having a high melting point; must possess high thermal shock resistance; and must have the capacity to withstand high temperatures.
Selecting Brick Type For Chimney Construction or Repair
Basically, there are 2 types of chimney bricks; calcium and clay.
Besides these brick types are several others that may be used for chimney construction. These include sand lime bricks, fly ash clay bricks, and engineering bricks.
The type of brick used for your chimney construction needs should be influenced by professional advice. In other words, you’ll need the help of a professional to pick the right brick for your chimney.
Let’s briefly discuss the different chimney brick types as follows;
Chimney Brick Types
Without a doubt, qualities such as durability and heat resistance should be basic characteristics of chimney bricks.
We’ve made mention of calcium and clay bricks as types of chimney bricks available. Asides from these are other alternate chimney construction bricks which will be covered shortly.
Calcium Chimney Bricks
These are also called calcium silicate bricks and are widely used for chimney construction. The reason for their use is evident in the basic characteristics of the construction material.
First off, calcium chimney bricks are known to be frost resistant.
Now, frost is an issue when it comes to choosing a suitable construction material. This is even more evident when because chimneys are largely exposed to harsh weather and the elements.
With its frost resistant nature, saturation is largely handled effectively.
Secondly, calcium chimney bricks are free from soluble salts. This makes them an ideal material for chimney construction. However, it’s always best to speak with a chimney service or expert before deciding on what’s best for your situation.
Due to prevailing environmental conditions as well as the availability of a chimney brick type, you may be advised to use a specific brick type for your chimney.
Of course, such advice should come from a professional to be valid enough.
Clay Chimney Bricks
Clay bricks are also among the chimney brick types used for construction.
However, it’s necessary to understand that not all clay types will be fit for chimney brick use. Certain designations are given to help with clear identification.
So, to find the best clay bricks for your chimney repair or construction, it’s best to seek the advice of an expert.
Considerations should also be made regarding the exposure of such bricks to weather conditions.
The nature of chimney construction means that bricks will be exposed. This may result in saturation due to weather action. Conditions such as sulfate attack and frost are common.
One way to protect such bricks is by having them capped at the top of the brickwork. Doing so will significantly limit exposure to moisture.
Other Brick Types
Asides from clay and calcium bricks, other types of bricks are available and can be used for chimney construction.
However, their use depends on advice from a professional. These bricks include sand lime bricks, fly ash clay bricks, and engineering bricks.
Sand Lime Bricks
Wet mixing is the chemical process by which sand lime bricks are made. These consist of a mixture of lime, sand, and fly ash. The result is a compressed brick that has a grey appearance with a smooth finish.
Fly Ash Clay Bricks
Fly ash clay bricks are also used for both chimneys and another masonry.
Basic ingredients for their construction include clay and fly ash. These bricks are also made to undergo high temperatures (about 3000 degrees Celsius) during construction.
However, one basic characteristic of this brick type is the fact that they expand when exposed to moisture or water. Based on this characteristic, provisions will have to be made during construction to keep moisture and water out.
When seeking to use water and moisture resistant bricks for your chimney, engineering bricks will naturally take a poll position. These bricks are constructed under high temperatures. Plus, they’re resistant to chemical action.
In terms of durability, these bricks are excellent.
Type Of Mortar Used For Chimney Construction
Having listed and discussed the different chimney brick types, it’s important to also consider the type of mortar being used. Certain mortar mixes are important for chimney construction based on durability classification.
More important is the risk of brickwork being saturated.
To guard against such, only sulfate resistant cement should be used as chimney construction mortar. This is largely due to the presence of soluble sulfates during flue gas condensation.
The type of chimney bricks has been discussed above. It’s important to always consider professional advice on the best brick type to use for your chimney repair or construction.