The choice of concrete blocks as material for building a retaining wall means preparing yourself for a good deal of physical labour. The blocks themselves are heavy and must be positioned by hand. For this reason, a concrete block retaining wall is best designed to be a rather short wall. You should also feel comfortable mixing and laying mortar if you want to build a concrete block wall.
Municipal Codes for Footings and Foundations
Always check with your local building codes before you commence to building your concrete block retaining wall. Best results are obtained by building the most solid footing or foundation possible. A check with the city construction authorities will provide you with information on how deeply you must build your footing or foundation to comply with municipal codes.
You can save yourself money and aggravation by making precise estimates of the amount of material that will be required for your wall. Begin by adding the length of all sides of your wall. Divide by the length of one concrete block, and multiply by the number of levels you plan for your wall, which will provide you with a good estimate of the number of blocks required for the wall, but add in corner blocks if you have built any corners into your design.
Start your construction of a retaining wall with a corner by building leads made of successively laid corner blocks. Disregarding this step will entail having to continually check the blocks to ensure they are level and plumb. By laying down corner leads, you need only stretch a mason's line from corner to corner, and follow the line to achieve a plumb and straight wall.
Run Mason Lines
An easy way to ensure that you keep the course of blocks straight and level is to run mason lines along the blocks for the entire length of your layout. Make things more convenient for yourself by keeping the lines a distance of 2 inches from the blocks themselves. This space facilitates easy measuring with a tape measure.
Keep the First Course Level and Plumb
Focus on ensuring that the first level of blocks is even and plumb. An even and straight first course increases your chances of the succeeding courses also ending up level and plumb. Repairing a major mistake on the first course is better than trying to line up succeeding courses evenly over a bottom level that you didn't ensure was level and plumb.
Cut Blocks to Fit
The necessity of cutting blocks to get a proper fit may arise during the construction of the wall. When you go to cut the block, add 3/8th inch width to your measurements to account for the addition of mortar lines. The cleanest cut of a block is achieved when the block is completely dry.
Concrete Blocks Over Cinder Blocks
Although it means more physical stress on your part, go with concrete blocks that weigh 18.1kg. or more. Breeze blocks are more lightweight and easier to handle, but the result will not be as strong nor as resistant to moisture as true concrete blocks.