How to Lay Concrete Block
If you've ever dreamed of a privacy wall, sleek grilling station, or some other concrete-based structure, now is your chance to build it. Laying concrete block for an outdoor project is surprisingly simple.
Get started by planning and snapping chalk lines. Then, spread mortar, place the blocks, and check for level. This tutorial explains how to lay concrete block in just six steps. Plus, we have a few expert tips that promise to make the job go off without a hitch.
What You Need
- Concrete blocks
- Story pole
Step 1: Start First Course
Start the first course by laying a mortar bed on the footing. Make it 1 to 1-1/2 inches thick and about three blocks long.
Step 2: Push in the Corner Block
Carefully push the corner block into the mortar bed, lining it up with the ends of the chalk lines on the footing.
Step 3: Check Height
Check the height of the block with your story pole, and push the block down until the top is even with the mark. If the block is low, pull it out, place more mortar on the bed, and replace the block. Then place a level on top of the block and level it along its length and width.
Step 4: Prep the Second Block
To prepare the second block, set it on end and butter its ears with a downward swiping motion of the trowel. Then press down on the mortar on the inside edge of the ear. This will keep the mortar from falling off when you set the block. If the mortar does fall off, start over with fresh mortar.
Step 5: Set Second Block
Set the second block in place, pushing it against the first block, making sure you leave a 3/8-inch joint space. Using the same techniques, butter the third block and set it. Don't remove the excess mortar on the footing until it has set up a bit.
Step 6: Tap and Continue Building
With three blocks laid, set a level on top and tap the blocks into place with the end of the trowel handle. Repeat the process on the width of the block. Check for plumb by holding the level against the side of each block. Then build the other corner and the leads.
How to Cut Concrete Block
Concrete block is made in so many configurations that you may not need to cut it at all. But if you do need to cut a block, place the block on sand or loose soil and use a brick set and small sledgehammer to score both sides of the block. Then set the block with its web up and place the brick set on the scored line. Strike the brick set until the block breaks cleanly. Wear eye and ear protection. You can also cut block with a circular saw equipped with a masonry blade. Wear eye and ear protection.
How to Reinforce the Concrete Block
Retaining walls and other walls subject to substantial lateral pressure (sideways pressure pushing against the face of the wall) require reinforcement. Embed reinforcing wire in the mortar of every other course, overlapping the ends by at least 6 inches. At a corner, cut and bend the wire 90 degrees.
To tie intersecting walls together, bend rebar into an S shape and embed it into the mortar as shown.
How to Tie Walls Together
Walls built perpendicular to each other must be tied together, and if you're putting up a new wall next to one that's there already, you can't place metal ties between the courses. Knock a hole in the core of the existing wall, stuff newspaper into the cavities, and place an S-shape piece of rebar in the hole. Then fill the holes with mortar and lay the next course.