Do It Yourself: A Quick Guide To Laying Concrete Block

Laying block might not be an easy task, but you can save alot of money if you take the time to do it yourself.

First off, choose the correct block for the job at hand. If you're unsure, ask at your local home improvement store or inquire with the block manufacturer, but 8" blocks are a standard size for most block jobs. Half blocks with square or rounded corners are often required at the end of a run. Single and double corner units provide a block that gives a smooth finish at the corner. Jamb joist blocks are used around doorways. Sash units provide an opening for casement windows, and header blocks are designed to provide a space for wooden beams or other structures at the top of a wall.

All block walls, no matter what size, need a secure footing of concrete. When using 8" block, the footing should be at least 8" deep and 16" wide. This footing will provide a 4" rim on each side of the block when laid. Make sure your footing is level by placing a level across the footings every 10". Before starting to lay the blocks, drive stakes into the ground and build a form at each corner. The stakes and forms can be made from scraps of wood. Find the exact corner by stretching lines from one corner form to the other. The exact corner will be the point at which the two lines cross. Determine the exact number of blocks required for the first run by laying out a course of block on the dry concrete. Be sure to use the corner blocks and cut blocks where needed. Use scrap pieces of 3/8" plywood to fill in the mortar joint between each block. This is the thickness of the mortar when applied.

After this test run, remove the blocks and prepare to lay the first course.



Drop plumb bobs down from the corner string and at positions about 3' out from the corner. Mark the location of the corner block on the footing base. Spread the mortar about 1" deep and 8" wide in the marked area. Extend this mortar out about three or four blocks in one direction. Put a furrow in the center of the mortar with a trowel. The furrow will push the mortar to the edge of the block when it's laid. Set the corner block first. Be sure you are using the finished end block. The starting corner block should be checked vertically and horizontally and positioned. Additional blocks will align with the starter block, so it's important to set it exactly. Follow this same procedure as you come to the other corners, laying the first course out about two or three blocks in each direction.

Tie a line between two bricks and stretch it between the two corner blocks on the first course. Lay the base mortar on the footing as you continue this run. Apply mortar to the ends of the blocks with a trowel and place the block in position. Keep all mortar joints at about 3/8". If you find it necessary to adjust the spacing, fill some mortar joints 1/2" to 3/4". If you must cut a block to fill a course, use a masonry chisel. Draw a line on both sides of the block where the cut is to be made. Strike the chisel with a bricklayer's hammer. After you've laid four or five blocks, check the alignment by using any straight edge. Check the tops of the blocks and the outside edge for correct alignment. Tap the blocks into position to make any alignment corrections while the mortar is still wet. Do not attempt to move a block after the concrete begins setting up.

Build up the corners first. Always keep the corners about a block or two higher than other runs until finished. Use a trowel to cut away any surplus mortar. Throw the surplus mortar back onto the mortarboard. Keep turning the mortar with your trowel during the entire project so it will not begin to harden. Use a piece of 3/4" plyboard or the bed of a wheelbarrow as a mortarboard. Always wet the board or the wheelbarrow bed before placing the mortar in it.

Never mix more mortar than you can use in a couple of hours. On a hot day, keep the mortar covered with a piece of plastic to prevent drying. Continue to stagger the blocks, working from the corners, and build the wall to the intended height. Measure both the length and the height of the wall after every two or three runs.

After all the blocks are in place, but while the mortar is still somewhat soft, use a jointer to finish the mortar joints. Keep the jointer wet during this part of the job. If wood framing will be attached to the top run, set an anchor bolt every 3' to 4' in the last run. If the concrete blocks are being laid as a fence, finish the top course by filling in the holes with fresh concrete mix. Patio blocks can be used for the final touch.

© High Speed Ventures 2011