How to mix concrete for making fake rocks

Introduction: How to Make Faux Rocks

How to mix concrete for making fake rocks

How to mix concrete for making fake rocks

How to mix concrete for making fake rocks

In this instructible, I present my first attempt at making a faux rock. I tend to do things the hard way, but also consider everything a learning experience, an experiment, if you will. I have since learned there are easier methods to follow, but again, this is my first attempt. My eventual goal: landscape my front yard (southern CA) so that I don’t have to water it ever again. Eventually, I will be able to build very large boulders using the techniques, and improvements I have learned, and save a ton of money on the rocks. Lets proceed:

Step 1: Gather Necessary Materials and Tools.

To make this rock, I started with a small corrugated cardboard box. I use lots of cardboard, so have a good supply on hand as well. Old newspapers for filler, some chicken wire, and of course cement/concrete tools such as spreaders, trowels, buckets, access to water, cement, sand and or mortar mix, etc.

Step 2: Design and Start Construction.

Thinking I could make a shape with cardboard as well, I made extensions out of cardboard that were glued onto the box with regular white glue. I let these sit over night to ensure that the glue was dried, and the bond was strong. It’s sometimes easier to do these type of projects in stages, no hurry, no rush.

Step 3: Roughout “rock”

Seen in this picture is the rough rock, and the spaces in between the extensions are filled with newspaper. I even used some styrofoam as filler or extensions as well. It doesn’t matter, you just want to make some support for your cement mix.

Step 4: Wrap Form With Chicken Wire

After enough newspaper and or styrofoam has been added to the “rock” form, it is all wrapped with chicken wire. I used the 2 inch size as it was cheaper, but 1 inch might be preferred. I made two layers of wire, thinking hole sizes would help hold the mortar better.

Step 5: Mix Your Cement/mortar

Following manufacturers guidelines, I use a mix of 3 parts sand to 1 part cement, with enough water to make a “stiff” mix of mortar. Using this basic formula, (it can be as much as 4 parts sand to 1 part cement), other variations can be tried. For example, I used a latex polymer tile set product as one part of the sand allotment. So it became: 2 parts sand, 1 part polymer, 1 part cement, plus the water. This adds some sticking power to the mortar mix, and makes it easier to control, I believe.

Step 6: Add Mortar Mix to Rock

Using a 3 inch spreader knife (drywall), I spread the mixture over the rock form. I started at the bottom edge of the form so that any loose mortar could be picked up and added to the rock before moving on. I set my form on a lazy susan turntable, covered in waste cardboard to make it easier to work around the form, and of course the cardboard caught the inevitable drips of mortar.

Step 7: Finish the Rock

After an overnight cure, the mortar was set enough that I could fill in any missed spots, or more commonly, places where the wire was showing through. To fill in these areas, I mixed some fresh polymer tile set, colored with cement colorant in a buff tone. This went on very easily, and towards the end, I added quite a bit of water to the mix, and using an old brush, covered the entire rock with the colored and diluted tile set. This dried very quickly, and I could stop here! To further experiment, I may try to add various weathering techniques,using acrylic paints to make “washes” of color, spattering with various colored paint, and so on. After curing for a few days, and finishing my experiments, I will seal it with a good exterior concrete sealer. This will help to protect the rock from the weather and prolong it’s life.

Step 8: The Outdoors Rock.

After finishing as described, I moved the rock out into the sunshine to further dry and “season”. Note it is still on the lazy susan so that I can rotate it throughout the day.

How to mix concrete for making fake rocks

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Rocks serve many purposes in the landscape, from acting as a border or edging to adding accents to planting beds. Purchasing natural rock for landscape use quickly becomes expensive and it may be difficult to find the exact color and size that you desire. Homemade concrete rocks make a cost effective alternative to authentic rock. Using plastic or rubber molds and a bag of cement mix, you can create the perfect rocks for your landscape design needs.

Put on a pair of rubber gloves to protect your hands while working with the concrete. Put on a pair of safety glasses to protect your eyes. Wear a dust mask to prevent breathing in any airborne cement mix.

Select a plastic or rubber rock mold in the desired shape and size. Place the mold on a flat surface with the depression facing upward.

Pour 1 to 2 inches of a mold release agent into a small bucket or container. Dip a paint brush into the agent. Brush the agent onto the surface of the mold’s depression. Push the brush’s bristles into small creases to ensure even coverage. Cover the depression completely with the agent to ensure that the concrete rock will slide out easily. Do not apply the agent to the point that it runs or puddles in the bottom of the mold.

Place a 5-gallon bucket on a flat work surface. Pour 1 to 3 pounds concrete mix into the bucket, adding only enough to fill the mold. Add water to the bucket at a rate of 2 1/2 tablespoons for every 1 pound of mix. Add the water 1 tablespoon at a time while stirring the concrete with a margin trowel. Continue to stir the mix until fully combined. Check to ensure that the consistency equals that of a thick batter. Add additional water if the cement appears too dry or additional mix if the cement appears too runny.

Pour a surfactant such as a glass cleaner or ammonia into a spray bottle. Mist the mold’s depression with the liquid. The surfactant will break the surface tension of the concrete and eliminate air bubbles from forming on the surface of the rock.

Pour the cement into the mold, filling the depression half full. Grasp the mold on either side and lift it up and down, tapping its bottom against the work surface to release air bubbles from the cement.

Pour additional cement into the mold, filling the depression full. Smooth the cement’s surface by dragging the edge of the margin trowel back and forth across the mold. Do not overfill the mold with cement. Leave the dividing sections uncovered if the mold contains more than one depression in order to keep the rocks separate. Drag a large-toothed comb or pick across the surface of the cement to create furrows if you intend to mount the finished rock on another surface.

Cover the mold’s top with plastic wrap to prevent the concrete’s surface from becoming dry. Wrap the plastic around the sides of the mold. Place the mold in a dry room with a temperature of 70 degrees Fahrenheit or higher. Position the mold in an undisturbed area, away from heating and cooling vents. Let the mold sit for 48 hours to allow the cement to set.

Check the cement every 4 to 5 hours for signs of moisture loss. Remove the plastic and mist the cement with water from a spray bottle if it appears dry. Replace the plastic wrap after misting.

Remove the plastic wrap after the curing time. Turn the mold over on a flat work surface. Lift the mold’s edges upward, bending them back slightly if necessary, to pull the mold off the cement rock.

Move the rock to an undisturbed area with a temperature of 70 F or higher. Leave the rock for seven days to dry completely.

How to mix concrete for making fake rocks

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Faux rocks, or fake rocks, are used in landscaping to create various structures. People choose fake rocks instead of real rocks for different reasons. Oftentimes, faux rocks are less expensive than natural rocks, are available in a variety of colors and sizes that fit different needs and are lighter weight than natural rocks, making them easier to put in place. Using faux rocks made of varying colors and textures, you can create quite a few formations and with a bit more ease than using real rocks would require.

Creating a Mix

Before you build rock formations made of faux rocks, the rocks must be on hand. They are made easily with a simple formula, which creates lightweight yet durable and realistic-looking rocks. The faux rocks are formed from a material referred to as hypertufa, which comes from the word “tufa.” Tufa is a lightweight, porous rock, and hypertufa is made to resemble it. The basic hypertufa recipe is 1 part course sand, 1 part cement and 1 part peat moss, all of which is mixed with water. The water needs to be added slowly and only to the point at which the hypertufa mix is wet and can be molded. It shouldn’t be so wet that it slips through your fingers.

Forming Rocks

A frame is necessary to form either solid or hollow faux rocks. Any object will do, but stiff wire netting works well if you want to mold the rocks’ shape yourself. Place the wire netting over a natural rock to use that rock’s shape, or make a shape of your own with the wire netting. If you want to create a hollow rock, then make the frame twice, and then stack the frames together and put a layer of fabric along the interior, concave portion of the inner frame to prevent the hypertufa mix from falling into that portion, which will be the hollow part of the faux rock. If you want to make a solid rock, then create a mound of hypertufa mix large enough for the wire frame to press against. When the wire frame is set for either a solid or hollow faux rock, cover the frame’s exterior with hypertufa mix while keeping the frame’s overall shape intact. Cover newly made faux rocks with plastic sheeting, and let them cure for five days before moving them, and let them cure one month before creating formations with them.

Making a Foundation

Every real or fake rock formation begins with an outline of the structure area and the digging of a trench. The outline can be formed either with stakes and twine for a formation with straight lines, such as a wall, or with a garden hose and spray paint for a formation with a curved or odd shape. After you outline both the inside and outside edge of the formation, dig out the area within the outlines to create a trench. Put a layer of gravel in the trench. Gravel will keep water drained from the formation’s base and will help you level and stabilize the formation’s first row of faux rocks. The faux rocks will be placed directly on the gravel.

Stabilizing the Faux Rocks

Unless you simply lay a single row of faux rocks or scatter a few faux rocks singly in your landscaping, you will stack multiple fake rocks on top of each other to create formations. Spreading masonry adhesive between rows of the faux rocks and along the rocks’ ends bonds the rocks together, which helps to stabilize the fake rocks, keeping them from shifting. Masonry adhesive is available at home-improvement and hardware stores. It dries quickly and shouldn’t slow your progress of building a formation. Stack faux rocks to create formations to your liking, ensuring they are no more than 3 feet tall for safety reasons. If you want taller formations, then work with a landscaping professional. Formations created with an odd number of faux rocks have a more natural look than formations made of an even number of fake rocks. Formations containing an even number of faux rocks look too uniform and structured to appear natural.

How to mix concrete for making fake rocks

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Rocks seem free and plentiful, found in nature along rivers and on mountainsides, but if you don’t have natural rocks on your property, you must pay a pretty penny to have rocks and boulders imported. Even if money isn’t an option, heavy boulders prove difficult to move throughout the garden. Instead, you can use peat moss and cement mix to make fake, porous rocks that weigh considerably less than the real thing. This mixture, known as hypertufa, imitates the appearance of tufa stone, a porous limestone rock. Customize the size, shape and color to suit your needs.

Dig a hole in a bed of course sand or in sandy soil in the desired shape for a large boulder. Select a shaded site that stays cool. If you want to make smaller rocks, dig smaller holes or use bowls or boxes as forms for the concrete and peat mixture.

Line the hole or mold container with sheet plastic. Cut the plastic large enough to leave some plastic overlapping the edges.

Mix 1 part cement with 1 part coarse sand and 1 part crumbled peat moss. Use 2 parts of peat moss to 1 part cement and 1 part sand to make even lighter rocks. Use a large plastic storage container or wheelbarrow and use a garden hoe or trowel to mix the ingredients.

Add water a little at a time and mix with the dry ingredients until you achieve the consistency of thick oatmeal. Squeeze a bit of the wet mixture in your palm; the hypertufa mixture should hold its shape well without squeezing out excess water.

Spray the plastic liner with nonstick cooking spray to make it easier to release the hypertufa mixture from the mold.

Fill the hole or mold with 2 to 3 inches of hypertufa mixture. Use a large stick to push the mixture down into the corners to fill the mold or hole well, while also removing air pockets that could cause the fake rocks to crack.

Add another 2 to 3 inches of hypertufa mixture to the mold. Poke the mixture with a stick to remove air pockets. Repeat this process until you fill the mold, leaving a few inches to the top.

Cut pieces of wire mesh hardware cloth or chicken wire, using a pair of wire cutters or tin shears. Bend the pieces into a wavy pattern, rather than flat. You can bend the wire on a piece of PVC pipe or similar object to achieve the wavy pattern.

Push the wavy hardware cloth or chicken wire down into the hypertufa mixture, leaving a few inches of space between each piece. The wire mesh helps reinforce the fake rock so it doesn’t crack or crumble. If you hit the bottom of the hole or mold, pull the wire up an inch or two so the wire doesn’t protrude through the rock.

Fill the hole or mold with hypertufa mixture up to the top edge, ensuring you cover all pieces of wire.

Cover the hole or mold with a piece of sheet plastic and leave it to cure in a cool, dry place for about two weeks. Remove the plastic once every two or three days and spray with a gentle mist of water. Regular misting keeps the hypertufa mixture moist, extending the curing process for a stronger rock.

Remove the plastic after a two-week period and check to make sure the rock is hard and completely dry. Dig up the rock from the hole in the sand, if applicable. Use a wire brush to remove any sand or soil, as well as to smooth out any rough edges. If you made the rock in mold containers, you can cut the sides of the containers or flip them upside down to release the fake rock.

Spray the hypertufa rock thoroughly with water once or twice daily for a period of about 10 days to leach out excess lime, commonly found in cement. This is not as important if you don’t plan to display the rocks near plants, but the excess lime raises the soil alkalinity if allowed to leach out among garden plants.

July 11, 2011 By Herb

It is easy to make fake (faux) rock covers to conceal valves, pipes and drip system distribution heads in your lawn or garden. This faux rock making tutorial shows you how to do it.

The art of making artificial (faux) rocks is easy to learn. Most of the materials are available through your local hardware store, such as Home Depot or Lowes, but you may have to hunt for a few items.

Faux rocks can be used for decorations around your home or yard and do not necessarily have to be used to cover yard objects. Although we did not include this in these instructions, if your finished rock is going to be more than one foot in diameter, it would be a good idea to start with a framework made out of chicken wire for additional strength and reinforcement. Projects for creating very large faux rocks or rock walls, such as those you see in zoos, require specially engineered supports to deal with the weight of the cement. Those projects are beyond the scope of this project.

Material List:

  1. Portland cement or type S or type N mortar cement (masonry cement). Portland is stronger, but mortar mix can be easier to work with.
  2. Sand. A bag of play sand, which can be found in any hardware store, will work great.
  3. Acrylic latex polymer. Males the mix sticky and easier to work with. It also help to create a stronger concrete bond.
  4. Cement dye or colorant. This comes in liquid or powder form and can be found at any major hardware store. Try a tan color.
  5. Concrete reinforcement fibers. We use polypropylene fibers, but any type of concrete reinforcement fiber will work. You can skip this part, but if your fake rock is exposed to extremes of weather it may crack.
  6. Polystyrene (Styrofoam) beads. This is the type of small beads used to insulate block walls. They are also used to fill some types of bean bags. The polystyrene beads component can also be skipped, but if you don’t use it your finished faux rock will be much heavier. Unless you live in a state with cold winters, you may have difficulty locating this product. We bought our polystyrene beads on eBay.
  7. Concrete sealer. Helps protect the faux rock from extremes of weather.
  8. Water.

Base Coat Mixture
Use a 5 gallon bucket and a large cement or plaster mixing paddle on an electric drill to mix the components. First combine 2 parts masonry cement and 6 parts styrene beads with a small quantity of fiber. Mix the dry mixture thoroughly with the mixing paddle and electric drill.

Combine 1 part acrylic latex polymer and 3 parts water in a separate bucket. Add most of liquid mix to the base coat mix and mix thoroughly. The final base coat mix should have the consistency of very thick peanut butter. If it is too dry or clumpy, add some more liquid mix.

Applying the Base Coat
Find a plastic bottle or disposable plant pot that covers the object that you wish to conceal. Trim the top or bottom as necessary. This will be the inside form for your fake rock. Begin working on a table that has been covered with plastic. The plastic surface will make cleanup much easier.

Use a margin trowel to start packing the base coat mix around the plastic form. Do not pack the mix uniformly. Start to form the rough shape of the fake rock that you wish to create. Leave the surface rough so that the finish coat adheres easily to the base coat. The base coat should be a minimum of 1/2 to 3/4 of an inch in thickness.

After the rough shape of the rock has been formed, allow the base coat to dry and cure for 24 hours.

Top Coat Mixture

The top coat is mixed similarly to the base coat, but instead of polystyrene beads we will use sand. Sand will give the faux rock a rough texture.

Combine 3 parts sand and 1 part masonry cement with a small handful of concrete reinforcement fiber. Mix thoroughly. Combine 3 parts water and 1 part acrylic latex polymer in a separate bucket. Add most of the mixture to the top coat mixture. Once again, the final mixture should be very thick, but workable with a margin trowel. Add liquid mixture as needed to achieve this consistency.

Add the colorant that you chose. We find that a tan colorant looks the best. Yo may have to experiment with the proper quantity of the colorant to add. That will vary based on the brand that you chose.

Use the margin trowel to pack the top coat mixture around the base coat. The top coat should have a thickness of at least 1/2 inch. As the top coat just begins to harden, you can texture the surface using a variety of methods, including dabbing the surface with a whisk broom, a rough sponge, crumpled aluminum foil or a crumpled plastic bag. There are lots of household objects that you can experiment with to simulate a natural rock texture.

After the top coat has been shaped and textured, allow it to dry for another 24 hours.

After the faux rock has dried, you can seal the surface using any type of concrete sealer. Be aware that some concrete sealers dry with a glossy finish, while others dry with a semi-gloss. The sealer is not absolutely necessary, will help protect the faux rock from deterioration and cracking due to moisture and freezing temperatures. After the sealer has dried, your faux rock cover is ready to use.

Do you know how to make rocks? I have been seeing more and more beautiful perfectly shaped painted stones. Did you know people are making their own stones for painting? I reached out to Happy Dotting Company to find out more on this amazing new trend of making stones!
How to mix concrete for making fake rocks

How to make rocks

Whether you have a hard time finding rocks in your area, you are looking for a perfectly symmetrical stone, or you want all of your rocks to be the same, making your own rocks for crafts might just be the thing for you!

This page contains affiliate links which means if you make a purchase using the link, I could receive a commission. Check out all the details here.

How to mix concrete for making fake rocks

Supplies for making your own stones

All you need to make your own rocks is a Happy Dotting Silicone Mold, in the shape of your choice and casting powder like Ultracal 30. Some alternative casting plasters include Quikrete, Dental Stone powder, Hydrocal powders. Crystacast or Herculite Stone (in UK) or Casting Plaster from Bunnings (in Australia and NZ).
Buy Your Rock Molds Here!

Step by step instructions for making rocks for crafts

How to mix concrete for making fake rocks

Starting with clean molds, measure out your rock mixture according to the package provided. Each mold you receive will let you know the volume of mixture to make. How to mix concrete for making fake rocks

Pour mixture into the molds. Set aside and let them cure for at least 6 hours. She suggests just leaving them overnight.How to mix concrete for making fake rocks

Next, peel your stone out of the mold. You will still need to let them dry for 2-3 more days, depending on your climate.How to mix concrete for making fake rocks

There will be a center dot on the round stones that you can use to start your mandala. This can also be rubbed off with a bit of sandpaper if you wish.How to mix concrete for making fake rocks

You can find more information about Happy Dotting Company on the Happy Dotting Facebook Page. There is also a full video tutorial below!

Use these perfectly round rocks to paint mandalas!

Anjela, the owner of Happy Dotting Company, always admired rock painting and so she decided to give it a go! Her first attempts were horrible and frustrating. So she developed a set of tools and practiced a lot! What a difference!

That was about 3 years ago. Since then she developed Happy Dotting Company to help other inspired artists on their creative journey. She fell in love with rock painting because it was so meditative, creative, and not to mention beautiful. How to mix concrete for making fake rocks

Most of her rocks are ornamental and so she has them placed around her house just for the pleasure of seeing them. The delightful colors and patterns can light up an otherwise dull space like a bathroom windowsill. She o ften gives them as gifts (sometimes with a written message).

Video tutorial on how to make your own rocks!