Landscape rocks give a natural look to garden designs.

Homemade Concrete Formula for Artificial Rock

by Jenny Green

If you have ever purchased and transported rocks to your landscape, then you may have promised yourself to find an easier method in the future. Faux rocks are so much easier to work with in the landscape. For thing, they are often lighter. And you can custom make them in the shape, size, colors and texture you desire. Cement and sand are the two must-have ingredients for making artificial landscape rocks. Add gravel to the mix helps keep costs down, and adding ingredients such as perlite and peatmoss helps create lighter rocks and different effects. You can also amaze visitors with family mementos embedded into your "ancient" garden stones and boulders.

1 Mix 1 part cement, 2 parts sand and 3 parts gravel to make a dry basic concrete mix. Add enough water to create a sloppy consistency, such as that of thick pancake batter, if you plan to pour the concrete into molds. Or stop adding water when the consistency resembles cream cheese if you plan to spread concrete over the inside walls of the molds to make hollow rocks. Continue mixing until the mixture is smooth and free of lumps.

2 Mix 1 part cement and 2 parts white or gray sand to create smooth, fine-textured faux rocks. Add enough water to achieve the required consistency.

3 Mix 2 parts cement, 3 parts sand and 3 parts perlite for a pock-marked effect. Add water until the mixture is crumbly like cookie dough. Press the mixture into the mold. Trapped air bubbles don't matter because they add to the effect.

4 Mix 1 part sand, 1 part cement and 2 parts composted bark or peatmoss to make hypertufa, which resembles a naturally porous, light rock called tufa. Add enough water to create a spreadable consistency.

5 Mix 1 part sand, 1 part cement and 1 part peatmoss or composted bark, and then mix in water, to make hypertufa that resembles limestone.

6 Mix 5 parts sand, 2 parts cement and 3 parts peatmoss or composted bark for hypertufa that resembles sandstone. Add water and mix.

Items you will need

  • Portland cement
  • Sand
  • Gravel (optional)
  • Perlite (optional)
  • Peatmoss (optional)
  • Composted bark (optional)

Tips

  • Basic concrete mix is available in ready-mixed bags.
  • Add water in stages when mixing concrete and hypertufa, and continue mixing for two or three minutes after the water is absorbed. Adding water too quickly can result in mixtures that are too sloppy.
  • To give artificial rocks an aged effect, paint them with a gray-green water-based latex exterior paint diluted half and half with water, then immediately wipe the paint off with an old rag. The remaining paint will have settled into crevices and imperfections. Rub the rocks down with grass or weeds to blend the color in and give the illusion of algae or moss growing.

Warnings

  • Cement can burn your skin and eyes. Wear safety goggles and gloves and rinse off any accidental splashes immediately.
  • To make concrete rocks that can withstand freezing temperatures without cracking. Use cement containing air-entraining agents, which add bubbles, or buy ready-mixed bags with this additive.
  • Hypertufa is slow to harden. Wait two weeks before moving rocks to their final positions. Hypertufa rocks made to resemble tufa are susceptible to crumbling after heavy frosts.

Photo Credits

  • Jupiterimages/Photos.com/Getty Images