The variety of concrete block fences today is staggering. Concrete fencing projects are limited only by imagination and budget. There are four basic types of concrete block wall components, each with their own design capabilities: basic concrete block, mortar block, non-mortar block, and precast concrete walls. All blocks are constructed the same way; concrete poured into a mould and allowed to cure. The purpose of the wall and the available budget will determine which type of components and installation process should be used.
Basic Concrete Mortar Block
Basic concrete mortar block is the type of block most people associate with block wall construction. There are three types of basic concrete mortar block: grey block, split face block and exposed aggregate block.
Gray block, also known as the "basic building block" of industry, is used in applications where aesthetics and beauty are not the primary concern. Gray blocks are installed using mortar, and are reinforced with steel in the interior channels.
Split face blocks are essentially grey blocks that have been altered to produce a rough, uneven surface on the exposed face of the block. Split face blocks are made by pouring concrete into a double mould. They are physically split apart after curing to produce two blocks. Split face blocks are installed the same way as grey block.
Exposed aggregate block is concrete block that has been sandblasted after curing. This process exposes the aggregate within the concrete, and provides a visually appealing texture on the block face.
Advanced Mortar Concrete Block
Advanced concrete mortar blocks are constructed to achieve unique visual effects when combined in a wall. This block type includes slump block, and Sonora or fluted block.
Slump block is a type of concrete block that mimics the look of adobe. It is uniform in size and shape but gives the appearance of irregularity. This block is also available in different size and colour combinations.
The manufacture of Sonora and fluted block uses moulds that create vertical lines and a textured face in the finished block. Sonora and fluted concrete block are popular with architects and designers. This type of block provides an inexpensive way to create unusual lines and textures in walls.
Non-Mortar Concrete Block
Three types of block do not require of mortar to hold them together. Rather, a system using gravity and special design characteristics keeps the wall intact. Non-mortar concrete blocks include landscape masonry, interlocking AB, and interlocking fence block.
Landscape masonry is a mortarless concrete block system that has specialised uses, and is favoured by architects because of the variety of block shapes and colours, and the ease of installation. Landscape masonry can be used as pavers for walkways, or to create landscape retaining walls (up to 6 feet high without reinforcement).
Interlocking mortarless AB concrete block is a stackable block system used to create visually appealing walls. Only one company currently manufactures AB blocks. AB blocks are extremely popular with contractors, and are available from any masonry supplier. AB blocks are available in a variety of sizes, shapes and colours.
Interlocking fence block is a hybrid in terms of installation. Mortar is used on the horizontal joint, but not on the vertical joint between blocks. The blocks connect using a tongue-and-groove design at each end of the block. These blocks are available in a variety of textures and colours, and are used primarily for fence applications.
Pre-Cast Concrete Walls
Pre-cast concrete walls are the most expensive method of constructing concrete block walls. Pre-cast concrete walls are made in large sections, transported to the job site, and installed by a licensed contractor. The variety of shapes, textures, and colour combinations are practically limitless.
All concrete block walls require foundation construction (or a footing) with one exception. Landscape masonry retaining walls less than 5 feet tall do not require a footing. Footings are typically constructed of poured concrete, reinforced with steel rebar, and finished so that there is a level base from which to build the wall. Hollow, concrete blocks are designed to provide for steel reinforcement, which is directly connected to the steel in the footing. Concrete is then poured into the interior channel of the wall with the steel in it. This process helps maintain the wall's strength and rigidity where external forces may act upon the wall.