Use a 5x8 to separate the blocks to account for the mortar.
How to lay out a concrete block wall.
Concrete block is made in so many configurations that you may not need to cut it at all.
The depth and size of the foundation will vary depending on the size of the concrete block wall and the weight it must support but a typical freestanding wall requires a foundation that is about twice as wide as the wall itself and which extends about 1 foot down below the frost line.
For ways to reinforce a wall of concrete blocks keep reading.
Lay out a course of concrete block on the dry footing.
Use a piece of scrap 3 8 inch plywood to fill in the mortar joint between each block.
To determine the width of your future wall decide how many cinder blocks you want to use for the wall width then calculate the width using the block s measurements.
For example if your cinder blocks are 8x8 in 20x20 cm and you want to use 2 blocks to make up the wall s width your total wall width would be 16 in 40 cm.
Do not use mortar for this test run since you re only trying to get an idea of what you need.
Use corner blocks on the corners if available.
The typical upright spacing for a block wall of any height is 24 inches to coincide with the cell openings in the concrete blocks.
Before you start lay out and pour footing lay out your concrete block in a dry run spacing it with 3 8 inch plywood spacers mark all the edges of the course.
Step 3 lay out the spacing for the uprights on the footing form boards using a pencil or carpenter s crayon.
The interlocking retaining wall block can be used to build walls up to 24 to 36 inches high depending on the size of the block.
Take up the block and spread mortar on the footing.
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.
Don t seal these down.
Then set the block with its web up and place the brick set on the scored line.
Use corner blocks where they are needed and cut blocks as required to make it all fit.
Avoid having downspouts pointed at the retaining wall and if it s against the house keep soil and mulch well below the siding.
Follow the block manufacturer s instructions for wall height limits.