How to Mold Outside Corner Blocks

Corner blocks present either added cost or a challenge during construction of a molded-block outside wall. Commercial molds for corners are expensive. Premade corner blocks constrain the user to making the wall the same color as the corner blocks, and laying the rest of the blocks around them in a manner that fits their standard shape. Now, it is possible to use some cheap materials and an ingenious little trick to lift all constraints. The most simple form allows production of 45-degree corners, but with modifications, any angle is possible.

ABS-plastic wall stone molds
Ruler
4-inch square deck post
Saw
Vaseline
Duct tape
Concrete mix

Instructions

- 1
  Lay down a mold, flange up, reservoir down. Measure with a ruler the distance between the mold walls that will form the upper and lower sides (the height) of the molded concrete brick.
- 2
  Measure off the distance from Step 1 on a piece of 4-inch-by-4-inch wooden deck post and make a mark. Draw a line around the post at the mark you made.
- 3
  Cut through the post at the line with a saw. Lay the piece edge-down into the mold, with the cut end and its opposite end wedged between the walls you measured. The sides of the four-by-four should come up from the bottom at a 45-degree angle.
- 4
  Apply a thin coat of Vaseline to the bottom sides of the four-by-four as a mold release. Tape down the block with duct tape --- from underneath one mold lip over the block edge, pulled tight, and underneath the other lip.
- 5
  Mix concrete and pour it into the mold on both sides of the block and allow it to dry for 24 hours.
- 6
  Lift out the wood block. Lift out each side of the concrete brick, breaking the thin center as you lift. Lay the pieces with the 45-degree surfaces mating to make your corner.

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