Hollow concrete blocks are a type of building material widely used in both the residential and commercial construction industries. Manufacturers make these blocks from cement, water, sand and aggregate, though exact formulas may vary. Standard hollow concrete blocks are shaped roughly like a number eight with squared-off corners and typically measure 16 inches long by 8 inches tall by 8 inches deep.
Hollow concrete blocks can be categorized as either split or smooth-faced. Smooth-faced are the most common, while split-faced units have a roughly textured surface that is often used for finished (visible) surfaces. They may be naturally gray or tan or dyed using pigments in the concrete mixture. These blocks are available in a variety of sizes and are divided into sections known as cells. While dual-cell units are the most common, four-cell and single-cell units are also available.
Builders use hollow concrete blocks to construct walls, floors and other structural surfaces both inside and outside a home. They are also used to construct footers and foundations to support a building and evenly distribute the load of the building. Most hollow concrete block structures are built using mortar, and many also require steel reinforcement to add strength and support.
Hollow concrete block is considered an economical alternative to solid concrete block. It can also be used in place of poured concrete (also known as cast-in-place concrete) or traditional wood or steel framing. Concrete blocks allow builders to construct some types of structures more quickly and economically due to the reduced amounts of mortar needed compared to what's needed when building with brick or stone.
Before choosing hollow concrete blocks for your project, consult a structural engineer or architect in your area for assistance with design.
Like all concrete products, hollow concrete blocks are known for their strength, sturdiness and durability. Structures built from these blocks are virtually soundproof and are highly resistant to termites and other pests. Concrete blocks offer a high level of wind resistance and are able to withstand harsh weather and a wide range of temperatures. Because they are hollow inside, these blocks also offer a high strength-to-weight ratio, which can reduce overall building loads compared to solid blocks or stone.
Many concrete products are considered unattractive and are not typically used as a finish material. While they can be painted to improve their look, concrete blocks are often hidden beneath other, more attractive finish materials. They are also relatively cold if left uninsulated and have none of the natural insulating properties of wood or brick. Finally, concrete blocks are heavier than wood framing, which could increase overall structural loads.