How to Make Fake Rocks with Concrete

Making fake rocks is a fast growing hobby and profession. Combining basic construction skills and artistic creativity you can create artificial rocks with concrete that are virtually indistinguishable from naturally occurring stone.

Fake rocks are quite inexpensive to make yourself and if it turnsout that you have an eye for sculpting you could find yourself in a new and profitable profession. From small stand alone stones like an address marker to a grotto covered hot tub or rock retaining walls or better yet–rock-climbing walls, artificial rock has many practical purposes. Note: where " Concrete" is referenced here, it is, in fact, " mortar." Concrete, by definition, also includes gravel or pebbles.

1. Build a form - You will need to use a form to build your artificial rock since concrete is very heavy. Make the bulk of the size of your rock from foam and cover with concrete at a thickness of 2-3”. This will make an artificial rock that feels and looks very real while being much lighter than real stone. You will need to wrap the form in chicken wire and steel reinforcement mesh so the wet concrete will have something to cling to on vertical surfaces and to provide overall cohesive strength to the concrete.

2. Mix concrete - This is done in a bucket by hand or with a point trowel, or in a wheel barrow with a pointed shovel, OR on a piece of plywood with a square head shovel OR in a cement mixer. These options are listed in order of smallest to largest batches of concrete needed. Mix 3 parts fine grade clean, washed sand with 1 part type 1 (also known as type 10) portland cement. For additional strength you can add glass fibers to your mix in small quantities. Wood glue, fly ash and silica fume are also used for professional level rock sculpting. Add water to a thick paste and mix a very, very long time before using. If your muscles are not burning you have not mixed it enough Texture the concrete - Use a sea sponge to create a pock marked, weathered effect.

3. Sculpt the concrete - Use a point trowel to sculpt the concrete after applying to the form. Become familiar with how rock formations look and plan to be patient. Sculpting rock is a very marketable skill and takes practice to achieve consistent results.

4. Texture the concrete - Use a sea sponge to create a pock marked, weathered effect. Texture mat imprints from real stones will drastically increase the cosmetic value of your rock. Nothing looks more like real stone than an imprint made directly from a real stone. Texture mats will also help to provide inspiration for the sculpting process as you can continue the veins by hand past the edge of your texture mat impression.

5. Cure the concrete - Concrete takes a full month to cure and is about 75% cured after the first week. If the rock is left to sit in direct sunlight during curing stage hairline cracking will be excessive. Soak with water often to minimize hairline cracking and proper curing.

6. Scrape the concrete - Wait a minimum of 3 full days of curing before commencing this stage. More if you are not in a hurry. Using a fine grit scraping stone grind the entirety of your artificial rock to remove rough edge that concrete has to the touch. When finished your rock with be smooth just like real stone.

7. Wash the concrete - Wash the rock thoroughly before proceeding to add color. Use a stiff (but not wire) brush to clean concrete dust out of all the nooks and crannies as this will look unsatisfactory later. Dry completely before coloring.

8. Paint the concrete - Using spray bottles and water based paints you will mist multiple layers of complementary colors over and over again to create a deep and realistic rock color. Inspect real stone closely to learn what colors produce which effect. Common upon close inspection of real rock are blue, green, red, orange, yellow, brown, etc. The higher quality your spray bottle system, the better your finished results. Ideally you should be able to gently mist each application of color without any blotching.

9. Seal the concrete - Use water based concrete sealant and apply 3 layers allowing time to dry completely between. Reapply once yearly via spray bottle to retain color.