Concrete Blocks - (Kentledge Blocks, Ballast Blocks, Kelly Blocks & 'Lego Blocks')

Kentledge Blocks, Kelly Blocks & Ballast Blocks - Find Out More

In this article we look at the properties and uses of concrete blocks commonly known as Kentledge blocks, ballast blocks, Kelly blocks and even Lego blocks.
kentledge blocks
The reason behind the name - Why are they called Kentledge Blocks?

The name Kentledge comes from the original term used to describe scrap metal and pig iron, specifically used as ship ballast in the 1700s. Over the years, the term expanded to refer to many other types of ballast weights and counterweights. Nowadays it is used to refer to the multipurpose, precast concrete blocks used in a variety of building applications. the term 'kelly blocks' is a shortened version of Kentledge blocks.

Ballast Blocks

The term 'ballast' is used to describe any sort of weighted object or material used to stabilise a structure or vehicle, most often a ship. Concrete ballast blocks are typically used in civil engineering and act as counterweights for a number of permanent and temporary structures such as fencing, hoarding, scaffolding and even marquee tents.

Lego Blocks

Lego blocks is an informal term used to describe Kentledge blocks due to their shape and stacking abilities similar to the classic children's toy.

Uses of Kentledge Blocks

Kentledge Blocks have many uses. One of the most common purposes of Kelly blocks is to create freestanding structures. Due to their unique design, builders are able to create sound structures and walls very quickly. Kelly blocks are ideal when erecting temporary structures as they can be removed just as quickly.

As well as structures and walls, Kelly blocks are also used as demarcation blocks, particularly in conjunction with roadworks. Thanks to their manoeuvrability, Kelly blocks make excellent demarcation blocks for temporary works such as this. Benefits of Kenteledge Blocks


As most Kelly blocks are used to create freestanding, temporary structures, this allows the blocks to be used over and over again.


Kenteledge blocks offer flexibility for site and project managers who may need to relocate temporary structures and walls.


Ballast blocks are highly durable structures and create even stronger structures when used together. Kelly blocks are so strong they can be used for retaining walls and storage bays. At Watts, our Kelly blocks are also frost resistant, making them ideal for outdoor structures.