Home and Garden | Repairing Individual Wall Blocks - Masonry & Concrete

One of the most economical masonry materials is concrete block. Typically used for walls and foundations, each block consists of an outside shell with a hollow center that is divided by two to three vertical webs. The ends of the unit may have flanges that accept mortar and join with the adjacent block, or they may have smooth ends for corners or the ends of walls. Although durable and strong, concrete block is vulnerable to extremes in weather conditions and with freezing and thawing it can crack and crumble.

If just the surface of a concrete block is damaged, the process of replacing it (see below) is relatively simple. To hold the block in place you will need to mix a small quantity of mortar. Masonry mortar contains cement, sand, and water. For small projects like this buy a prepackaged mortar mix. These mixes are a bit more expensive than making your own, but they require only the addition of water at the project site. Refer to the package label for specific instructions on mixing, using, and curing the mortar.

PROJECT BASICS

Project: Moderate
Estimated Project Time: 1 hour
Start Tips: Have all your tools and materials ready before you start
Safety Tips: Wear work gloves, safety goggles, and a dust mask when chipping or cutting cement block
Recommendation: Do-it-Yourself

Fig. 1

INSTRUCTIONS

1) Drill holes through face of block
For many repairs, you don't have to remove the entire concrete block, only the face. To begin the process, drill a series of holes through the face using a power drill fitted with a masonry bit. (Fig. 1) Wear safety goggles, a dust mask, and work gloves to protect yourself.

Fig. 2

2) Remove the face of the block
Using a brickset and a small sledgehammer, chip away the face of the block, the interior webs of the block, and the mortar that held it in place. (Fig. 2) Then cut a replacement to fit the area. To cut a concrete block by hand, place the block on sand or loose soil and then using a brickset and small sledgehammer, mark the cut on all sides, turning the block as necessary. Keep working along the lines, first using light pressure then striking harder until the block breaks.

Fig. 3

3) Set the new block face in place
Using a bucket and trowel, mix up a small batch of mortar mix, following the directions on the package. Butter the back edges of the block with mortar, then set it in place. Using the point of a trowel, force mortar in around the edges of the block and then use a jointing tool to smooth it down. (Fig. 3) Allow the mortar to cure and dry properly. Use a small piece of concrete block to scrape away residue.