Few Building Materials Can Stack Up to Concrete Blocks

Concrete blocks are hard to beat in terms of price, versatility and ease of use. They’re heavier than bricks and more utilitarian than either bricks or stones.

First produced in 1882, concrete blocks are newcomers compared with such ancient masonry materials as stone and brick. Usually only one width thick, concrete block walls are less expensive and easier to build than brick walls. If appearance is a factor, you can use decorative blocks, or veneer a plain block wall with brick. Among the many uses for concrete blocks are as foundations, exterior and interior walls, retaining walls and garden screens.

Hollow-core blocks can be filled with insulation. They can also be reinforced both vertically and horizontally. When planning a concrete block structure, make sure to check local building codes for reinforcement requirements. This is especially important if the structure will be exposed to high winds or is in an active earthquake zone.

Standard blocks are precision molded from a mixture of portland cement and gravel or crushed-stone aggregate. Lightweight blocks contain such aggregates as pumice or expanded shale, slate, clay or slag. They’re easier to handle than standard blocks but slightly more costly.

Blocks are available in many decorative styles and finishes and functional shapes. They can be solid or hollow or have preformed insulating inserts.

By the Numbers

The most commonly used concrete block is the hollow-cored stretcher, which measures 8 inches wide, 8 inches high and 16 inches long (nominally, allowing for three-eighth-inch mortar joints between blocks).

Concrete blocks are also made in other even-numbered widths from 2 to 12 inches; in half-height (4-inch) and half-length (8-inch) units. Not all types and sizes are available in all areas. When planning a block structure, consult local masonry suppliers first.

Standard stretchers weigh about 40 pounds each, lightweight versions as little as 25 pounds. The sides of stretchers are called face shells. Stretchers usually have flanged ends and two or three hollow cores (“cells”). The cores are separated by partitions (webs) that taper from top to bottom, making it easier to grip the block.

Corner blocks resemble stretchers except that one or both of their ends are flush. In a wall without corners, 8-inch cubes called half blocks are set at the ends of every other course. Partition blocks, 4 inches or 6 inches wide and flush at both ends, are used as backing for stone or brick veneer as well as in interior partition walls. Specially shaped units are available for use around door and window frames and to form control joints that accommodate the movement of the masonry.

Stylish Choices

There are several decorative styles:

* Split blocks are cut apart to produce a rough, stonelike texture on the exposed surface.

* Slump blocks resemble adobe.

* The exposed surfaces of architectural blocks are ribbed, fluted or otherwise patterned.

* Screen or grille blocks are cast with a graceful decorative pattern to make attractive dividers and garden screens.

* Ground-face blocks are ground smooth to resemble terrazzo flooring.

Tips

To reduce the need to cut blocks, plan your project so that all dimensions are multiples of half- and full-size blocks. A masonry supplier can help determine how many blocks and how much mortar will be needed.

Have the blocks delivered as close to the work site as possible.

Store them on a dry platform and cover them with a sturdy plastic tarp to keep out moisture and dirt. Unlike bricks, concrete blocks must be dry when laid in a wall.