How to Build a Concrete Block Wall

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NOTE: When working with cement-based products, always wear eye protection and waterproof gloves.

Laying a concrete block wall with mortar joints takes careful planning, but it can be accomplished by do-it-yourselfers with a bit of practice.

Step 1: Concrete Block Wall Footing

All concrete block walls—both structural and non-structural—require a solid, poured concrete footing. QUIKRETE 5000 is the recommended product for footing construction, due to its high cured strength and rapid strength gain.

Poured concrete footings should be at least twice the width of the concrete blocks used. Standard 8” x 8” x 16” blocks would require a 16” wide footing. Make sure the footing depth extends below the frost line, and check local building codes for construction requirements in your area.

Tie rods should be set a minimum of 6” into the concrete footing for load bearing concrete block walls. Rebar should be placed in every other masonry core to provide structural support.

For masonry cores over 4” wide, pour QUIKRETE Core Fill Grout Course around the rebar. Use QUIKRETE Core Fill Grout Fine for masonry cores that are less than 4” wide.

Step 2: Layout Concrete Block Wall

Layout the first course of block on the footing, leaving a 3/8” gap between the blocks to allow for the mortar joints.

The actual measurement of a standard 8” x 8” x 16” concrete block are 7 5/8” x 7 5/8” x 15 5/8” to accommodate the mortar joints.

Step 3: Mark Concrete Block Wall Location

Mark the location of the wall on the footing, then remove the blocks and pop a chalk line on each side of the wall location to act as reference lines.

Step 4: Mixing Mortar Mix

Use QUIKRETE Type S Mason Mix for laying both structural and non-structural block and brick walls. This preblended mortar mix is very workable and achieves the high bond strength required for a concrete block wall. One 80-pound bag of Mason Mix will lay up to 13 standard concrete blocks.

The proper mortar consistency is achieved when wet mortar will hang on a trowel held at a 90° angle. Before placing a trowel full of mortar, gently snap the trowel downward to remove any excess mortar.

Step 5: Apply Mortar to Footing

Mortar for a concrete block wall should be workable while firm enough to support the weight of the blocks. Before applying mortar mix to the concrete footing, dampen the surface of the concrete slab with water.

Place a 1” wide bed of mortar on the footing, then use the tip of the trowel to create a furrow in the center of the mortar to distribute it evenly.

Step 6: Lay Corner Blocks for First Row

Set one corner block into the mortar bed on the footing so it forms a 3/8” high mortar joint. Check that the block is both level and properly aligned, and remove any excess mortar.

Following the same procedure, position the corner block at the other end of the wall on the concrete footing.

Step 7: Lay Remaining Blocks in First Row

Lay the remaining concrete blocks in the bottom row by buttering one end of each block, and positioning it next to the adjoining block. Press each block down into the mortar bed and against the previously laid block so all mortar joints are 3/8” wide.

Adjust each block so it’s flush and level. Continue this process until the first course is complete.

Step 8: Set Half Corner Block in Second Row

Apply a 1” thick mortar bed along the top of the first course of concrete blocks. Set an 8” x 8” x 8” half block into the mortar bed at the end of the wall that had a full corner block on the bottom row to create a strong running bond pattern.

Step 9: Lay Remaining Blocks in Wall

Continue adding concrete blocks to the second and subsequent rows until the wall is complete. Use a mason’s line as a guide to align the blocks in the wall.

Step 10: Smooth Wall Joints

After the mortar joints have become firm and thumbprint hard, use a jointing tool to smooth the joints and remove any excess mortar before they harden.