DIY Concrete Edging Molds
Molding concrete edging is a two-part process: creating the mold, then molding the edging. Simple edging molds can be made with rectangles of wood; fancier molds can be created by using roof flashing to create a shaped edge. The secret to successfully molding concrete is to keep the object damp on the outside for several days to allow it to cure from the center out. Curing hard on the outside first can cause your project to crack and crumble. Does this Spark an idea?
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Things You'll Need
- 2-inch by 4-inch boards
- 10-inch aluminum flashing
- 1-inch by 2-inch furring strips
- Plywood
- Saber saw
- Hammer
- Nails
- Pourable rubber
- Motor oil, Vaseline or PAM
- Air dry clay
- Commercial release agent
- Safety goggles
- Rubber work gloves
- Breathing mask
- Rubber tub
- Trowel
- Portland cement
- Sand
- Towels or sheets
- Plastic sheets
Instructions
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Make paper patterns of the footprint and side view of your mold. Use this for reference. An easy edging to make is a simple rectangle. Measure and cut 2-inch by 4-inch boards to frame a rectangular opening the length and height of your planned edging. Fasten them together with wood screws. Place the board frame on a piece of plywood or other flat, movable surface.
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2
Line the mold with plastic. Lightly spray the inside of the plastic with PAM or any other oily substance. Put on safety gear -- gloves, mask and goggles -- before handling dry cement powder. Mix one part Portland cement with three parts wet sand. Add enough water to make a stiff mixture -- about the same texture as biscuit or cookie dough.
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Trowel the mixture into the waiting mold, cover with a damp cloth, then with plastic. When the concrete has set, unscrew the wood, and pull it away from the concrete, but do not move the object. Lightly spray it with water and recover it with the damp cloth and plastic. Continue the dampening process for three days, then let the molded edging dry completely.
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4
Use shaped edging for one edge of the mold. Measure a consistent interval along the flashing. At each interval, score a crease across the flashing. Draw an arch on a piece of plywood and cut it out using a saber saw. Tack one end of the flashing to the flat side of a furring strip. Place the pattern arc under the flashing and bend the flashing over it. Secure it to the furring strip with a small nail. Move the pattern arch to the next section, and repeat. Insert the series of arcs, open end down, into one edge of the mold box.
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5
Pack wet sand inside one edge of the mold and pat it into place to form irregular, organic shapes. Use plastic film to help hold it into place as you add the concrete to the inside of the mold.
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6
Create a rubber mold for the most complex shapes. Seal the inside of your rectangle of wood board with shellac or polyurethane. After it dries, spray it with a commercial release agent. Make a model of the edging using air dry clay. Pour a layer of rubber into the bottom of the board rectangle. Place the model on top of it and pour rubber around it. Let the mold dry and pop the model free from the mold.
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Spray the inside of the mold with a water-based concrete release agent. Trowel and pat the wet cement and sand mixture. As with the wood mold, keep the object moist so that it can cure slowly.
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