November 28th 2019
Engineering bricks are a specific type of brick used for their physical properties, rather than their appearance. They are used in a structural capacity, most commonly in foundations below the damp proof course as they are manufactured to high specifications in compression strength and water absorption.
Think of the engineering brick as the functional, no-frills brother of the more refined, facing brick.
That's not to say they can't ever be used for aesthetic purposes though and we'll look at that later on. For now, here's all you need to know about Engineering Bricks.
If you're building an extension for example, you need to make sure the foundations are secure and will stand the test of time. It would also be a real shame to waste the aesthetic qualities of facing bricks on foundations that are just going to be covered by mud.
This is an occasion where engineering bricks come in.
Engineering bricks are manufactured to be highly durable, water-resistant and have a high compression strength. Because of this functionality, they're not checked for aesthetic discrepancies to the same extent as facing bricks. It doesn't matter so much if the colours are a bit off or they've been ever so slightly chipped because they're mainly there to stop the building collapsing, not get people to look at it.
They've been used on everything from the smallest extensions to bridges, canals and even the foundations of the Empire State Building.
The base of the iconic New York Skyscraper was built using red Accrington bricks, famed for their supreme strength and made not far from the Lancashire town where they get their name.
These bricks, also known as 'Nori' bricks partly due to their 'iron' like strength are a classic example of how engineering bricks are made. Part of the strength is down to the clay used but the bricks are further strengthened during the manufacturing process.
Engineering Bricks are separated into two different types - Class A and Class B. These denote just how tough and durable the brick is.
Here's a summary of the differences:
Class A bricks have a compression strength of 125 N/mm² and a water absorption rate of less than 4.5%. More often than not they're blue or red. These are used for more intensive purposes, larger buildings for example that require the highest strength.
Class B, are also normally blue or red and have a strength of 75 N/mm² and water absorption rate of less than 7%. There's a larger spread of these as they are generally used for normal housing and commercial properties of a more standard size.
Engineering bricks get their strength primarily from the firing process during manufacture. The clay used will have been chosen for its durable properties and when fired at a regulated high temperature, the molecular structure hardens.
So why are some bricks blue I hear you ask? Believe it or not, the blue colour is not a dye or colouring applied. They turn blue as a result of the way they're made.
Blue bricks are originally red clay but are heated at such a high temperature in a low oxygen environment that the clay turns blue and develops its impervious surface in the process.
Besides foundations and groundworks, engineering bricks have many other useful purposes.
One common use is to create damp proof courses. These are barriers designed to prevent moisture rising in a structure. Engineering bricks are of course used because of their low water absorption.
They have also often been used in the construction of bridges, tunnels and other integral structures due to their high compression strength. If you're bearing a lot of weight, you're going to want a building material that can handle it.
We did mention you could use engineering bricks for aesthetic purposes as well.
There's nothing stopping anybody using them for a whole building but it's generally not recommended as the bricks won't have undergone the same quality checks as regular facing bricks. The difference in aesthetic checks means that one batch to the next can have a different look, making it difficult to match for an extension or buy a few more packs to complete the project.
As well as the visual faults we mentioned at the beginning, the brands may even be mixed by distributors, so not all the bricks will necessarily be identical.
Engineering bricks can usually be identified by their smooth robust exterior and simple wire cut construction. Now, most buildings wouldn't look great with a plain, smooth exterior. Bricks are generally chosen for their texture and character.
But if that's not a concern, they can add a unique flair. Blue bricks particularly are quite popular for certain projects due to their unique look.
This is a trend that has been used in a lot of contemporary architecture since the 1960s but the use of blue engineering bricks for buildings dates back even further than that.
If you're building something, you're going to want to know about engineering bricks. They're a fundamental part of building a structure and are surprisingly versatile. We hope we've highlighted the differences between these and facing bricks to make sure you get the right ones for your project.
Let us know about your project at the earliest opportunity and we can help you plan for the bricks you'll need in advance.
If you want to see what engineering bricks are on the market, view our brick library and let us know how many you need.
Once you've got those sorted, you need to choose the aesthetic facing bricks - more related to the visual appeal of your property.