Bricks that have holes in are engineering bricks. What are engineering bricks? Why do bricks have holes in them? Why do we use engineering bricks? These are common questions that are asked and the answers are straightforward and easy to understand.
What Are Engineering Bricks?
Engineering bricks are bricks that have an increased strength compared to their regular counterparts. As a result, they give a wall or building better structural and technical characteristics. There are two types (Class A and Class B) of engineering brick, having different compressive strengths. Class A engineering bricks have a strength of 125 N/mm2 and water absorption of less than 4.5% whereas class B engineering bricks have strength above 75 N/mm2 and water absorption of less than 7%.
Why Do Engineering Bricks Have Holes In?
Engineering bricks are easily recognisable because they have perforations through the top to the bottom. Basically they have holes in. Standard engineering bricks have three holes in but why?
- Structural – One reason engineering bricks have holes in to allow connection to other bricks within the wall. When applying mortar to the bricks, it seeps through the holes. Once it has hardened, any stresses in the brick are transferred to the mortar minimising any movement and distributing strength. The process essential locks the bricks together. Structural reasons are not the only
- Weight Saving – With three holes in the brick, material is removed from resulting in a lighter brick.
- Cost Saving – Related to the point above. As the brick has less material, it is cheaper for manufacturers to make therefore cheaper to purchase.
- Heat Distribution – The holes in the brick allow it to have a more consistent heat distribution throughout the brick as it can easily penetrate. The benefit of this is seen during the cooking process to make the brick as it allows the brick an even cooling rate and cure.
What Are The Different Types of Holes in Bricks
There are different types of holes in engineering bricks: core holes and frogs (more like a recess). Bricks with frogs have an indentation on one side, which provide the benefit of a smooth finish. These type of bricks are known as frog bricks. On the other hand, bricks with core holes generally have three holes, like in the image above.
Both types of bricks have the primary benefits as discussed above.
Why and When Are Engineering Bricks Used?
Traditionally, engineering bricks are used in construction when strength and resistance to water and frost attack are of importance. Engineering bricks were used in the construction of the foundations in the Empire State Building. They are not used for their aesthetic value, making them uncommon for face facing bricks. Engineering bricks are also commonly used for damp proof courses.
Summary
Engineering bricks are traditionally used to make the most of their increased strength and not their aesthetic value. They have perforations through the top to the bottom, which serves the primary purpose of allowing the bricks to be locked together, achieved by allowing mortar to seep through.