Wednesday, November 11, 2009

Fake Rocks & Boulders

Making Artificial Rocks
(c) 2009 Some Rights Reserved
by Tom King

A friend of mine makes his living building rocks and designing exhibits for zoos and theme parks. Billy Williamson’s notable work is incredibly lifelike and graces zoos and theme parks all over the country. He kept pestering me to come and help him work on a structure he called a "feed lot for Rose Queens". The structure was a backyard waterfall, stream and swimming pool in the backyard of a local member of Tyler, Texas high society. The waterfall includes a Batcave-style garage underneath the falls where the owner planned to store his Bentley. I finally agreed to join his crew for an afternoon and found myself in welding gloves with an odd bending tool, bending and tying ¼ inch rebar in the Texas summer sun. I was sore for a week. What I learned:


The first part of building artificial rocks is to create the basic shape. You do that by driving rebar into the earth and then using a bending tool to create the skeleton of the rocks and boulders you plan to construct. The vertical rebar, once bent is cross braced by laying horizontal rows of light rebar tide at the point where the bars cross. The tying is tedious, but if you use standard tie wires and a wire tying tool, you can make pretty quick progress. So long as you keep the bars close together and don’t make gaps too large, it’s pretty hard to mess things up. Leave room under the rocks to crawl around under there because you will need to place plastic sheeting behind the rebar.


Attach heavy gauge plastic sheeting behind the rebar. Use wire ties to pull the plastic up against the rebar to prevent pooling of concrete behind the rebar. Be careful not to rip the plastic. Duct tape can be used to cover tears and holes.

Chicken Wire

Chicken wire makes a perfect framework for the surfaces of artificial rocks. It is shapable, easily cut and quickly attached to the rebar framework. Once all the surface of the structure is covered with chicken wire, go back and tweak the shape a little. Make boulder shapes, cracks, crevices and ledges as you go. Use your creativity. You can even create artificial tree stumps, fallen logs and other natural looking bulky structures.


There are two ways of applying the concrete. Lightweight vermiculite or gunite normally used in swimming pools and decks works very well here. The only problem with using a pump, you have to finish the job in one go. For large jobs, this may not leave adequate time to do basic sculpture. To get the proper look for rocks, mix gunite or vermiculite concrete in a wheel barrow and trowel it onto the wire frame. You’ll have to play with the thickness of the mixture to insure it penetrates the wire and rebar without being so thin it is runny. Build up a layer that is at least an inch an a half to 3 inches thick and smoothly covers the rebar and chicken wire. In some places the coating of concrete will be thicker to fill gaps between the chicken wire and rebar. Make sure the rebar below is covered so the rock formation will be strong. Use a flat trowel to smooth the surfaces into the basic rock shape. Do a section as large a section as you can do in half the time you have for the day. Work from the bottom up and apply gently so as not to break through the underlying layer..


When the first layer is partially cured, mix up  a sand aggregate concrete mixture (the kind used for stucco walls and similar surfaces and start at the beginning of the base section you just did. Spread a thin layer of wet finish over the concrete base. You may mix rock colored surface stain in with the mixture or spray coat it on later if you have any special effects in mind. Cover the surfaces of the concrete shapes completely.  Go section by section so your working surface doesn't dry before you can texture it.


Next, cover the large flat areas with aluminum foil. Do not crumple the foil, but wrinkle it just a little bit and then spread it over the still wet ‘rock’ surfaces and press down firmly as shown in the picture. The foil will give the ‘rock’ surfaces a natural texture.


After about 5 minutes, remove the foil and use the edge of the trowel to etch a few cracks into the concrete and to trace seams and layers between separate rock shapes. This takes a steady hand, but don’t make the lines too straight either. Vary depth and width of surface striations to imitate features of natural rock. Lightly brush the rock surface with a paint brush to remove concrete crumbs and create a weathered look. Allow the concrete to set overnight before putting weight on it.


Once the “rocks” are set and dried, brush or spray on stain. Even if you applied stain to the finish itself, you should add contrasting colors to accent cracks, seams and shadows. It requires an artist’s eye and a lot of practice as you can see from these shots of Billy Williamson’s finished projects. It’s an art form and if you ever get a chance to work with someone like Billy who understands it, take the job! Mimicking Mother Nature is a whole bunch of fun!

This is one of the exhibits at Tiger Creek Wildlife Refuge that Billy designed and help build (below).  Tiger Creek is home to a large collection of rescued tigers, tiger cubs and other big cats located just north of Tyler, Texas.  Tiger Creek is a not for profit organization providing rescue services and shelter care for tigers and big cats.

These tigers below are enjoying the summer sun sprawled on the waterfalls and rocks built by Billy and the volunteer crew and Tiger Creek staff.

 These guys play rough, but the rock formations can handle the pounding.

 This next exhibit was built for a Tennessee zoo by, also by Billy Williamson.  The black bear in the exhibit enjoys the waterfall and stream in his new home.

This fat bear is having a little soak.  Not a single rock here is real.  All were sculpted by hand using the method described above as was the creek below in a chimpanzee exhibit.

Note, there is not a single loose item in the picture below.  Chimpanzees love to throw rocks and loose objects.  Billy's knowledge of chimp behavior led to this design in which everything in the river is part of a single piece of concrete, sculpted and staied to look like an ordinary stream full of rocks and deadfall trees, but without the hazard to keepers and visitors of having a loose rock heaved at you by a mischievous chimp.

Photos (c) 2009 by Tom King, Tiger Creek Wildlife Refuge and Billy Williamson (All Rights Reserved) 


  1. Quite detailed and thourough I'd say, but quite the long trail if wanting to do a smaller quicker process. Try this if you are doing a smaller project:

  2. This article was specifically designed for folk wanting to do a larger, more detailed project. And Billy's work is as much art as it is construction, so perhaps I should have included a caveat about this being a bit more ambitious than simply throwing down a few fake boulders.

    If you're just accenting a patio, you can always go down to Home Depot and buy a simple stone walk mold for about $20. It works well if you want to build a fake stone walk out of concrete and creates a surface that looks like mortared stonework. You can use it to face a stone wall, floor a patio, make a sidewalk or create an attractive "pile o' stones" accent. It looks neat and the hard plastic mold comes with detailed instructions for how to lay the concrete. You can even use some of the techniques shown here to make the "rocks" look more realistic.

    Good luck selling your book, though. Looks interesting.

  3. Mr FixIt

    i like you was not a chosen one to be wealthy with money. But I am wealthy in heart and soul, which to me is MORE important, for money is monetary. But Being given the hands, brain and willpower to create is undoubltly the absolute grandest of all wealth! I am a self taught artist, and i have taught myself how to build boulders. I have known about the rebar process for the larger boulders but didnt was a little intimidated by the rebar. I am not anymore, as my plan is to construct 3 or 4 huge boulders in my frontyard, i just finished 5 boulders of approx 4' long, by 2 to 3 feet wide and only 24 " in height. BUT i want the next ones to tower up to 6'tall 4 to 5 feet wide.. im excited to get started, i have to go buy a rebar bender. i think the only challenge i will face is the tying of the rebar properly. I want to thank you for the amazing insight of your experience. The boulders are INCREDIBLE!! AMAZING work!! I hope mine turn out as wonderful as these are... oh , by the way , Im a
    mother of 3 beautiful children and i have taught them that if you put your mind to anything, you can do it! and the only way to be successful is to face your fears head on. and IF we fail, get up and do it again!! thank you again for the great tips!!debora.. muralsbydebora@yahoo

  4. Anonymous(poster) above touting is spam - just trying to sell video. Don't waste your time.

  5. Where does Billy Williams live?
    How can I contact him?

  6. Billy lives in Tyler, Texas. You may be able to find him in the directory. He spends a lot of time on the road. He does a lot of projects for zoos and theme park kinds of things. Brian Werner at Tiger Creek Wildlife Refuge probably has his cell number. I haven't seen Billy in more than a year and lost his number in my latest move. I'll see if I can find his number if you'll send me your phone number through my Facebook account, I'll text it to you once I've got it (if you can't find it). My Facebook ID is twayneking.

    1. I am always so fascinated by the structures at theme parks and such that after the first few times, waiting in lines is spent observing, wondering how, and considering how I could do such things. Always wondering how they did it. Most recently, a trip to Magic Kingdom allowed good insight by observing the soon coming Snow White and Seven Dwarves ride to open next year. They were doing the same thing basically. I'm also wanting to do a smaller water fall and fire pit feature in my back yard so I decided to do research after I realized that's got to be my method of forming the structure. Still planning- thanks

  7. When making one continuous creek bed and waterfall can it be done in sections? Is there a time period you can have lapse between the start and eventually finish of a long continuous project like a creek bed? I guess what I mean is, if one starts and stops will the next section adhere to the previously done section ? Jane

  8. You have to on larger projects. Billy typically works on them in sections when he's doing zoo exhibits or large projects that can't be done in one swoop. It works the same way tall poured concrete structures work. Just make sure the areas you will join are clean on the older section and the concrete will adhere just fine. Good luck with your project.

  9. What is the actual structure behind the rebar, is that just dirt or clay or something and if it is what do you mean leave room behind the rebar to crawl around. The picture does not look like there is room behind to crawl around

  10. You are basically building a rock shell over either a hollow space or over dirt, foam blocks or something to give the outer surface a bolder shape. Roofing paper works as does sheet plastic for backing the rebar. Shaped chicken wire is also useful to provide a backing for the rebar when you apply it. Any of the techniques swimming pool builders use can work for you. The only difference is that you are creating free form shapes that bulge outward rather than bowl shapes that bulge inward.

    You can fill the empty spaces with dirt or sand - virtually any fill material. If you are placing pumps or electrical lines inside the rocks, leave it hollow and provide discreet access panels at key points. There are all sorts of interesting things you can do if you've got the creative bone in you.


  11. Tom, if you are mixing your own cement, will a type n motar mix work or what would be the best type to use? I am planning on making steps up my back hill as well as some boulders to go along side it and would like to know the best mix to use. My backyard is too far away to bring in a truck as well as it being up a hill too.

    1. Billy recommends a sand aggregate concrete mixture (the kind used for stucco walls and similar surfaces). Something about mortar mix being too brittle.

  12. What type and brand of stain or paint is used. I am rdering soon so want to get this correct.

  13. Concrete looks like rock, so most folk don't bother to paint it. Almost any concrete paint would work, but be careful. Paint can make the boulders look fake. If you want to create stress lines or color textures, you can probably use concrete stain. You'd have to experiment with the colors and application. Myself, I wouldn't paint it. I'd let the concrete weather and discolor naturally over time just as real boulders do. It'll even grow moss on it if conditions are right.

  14. We always used concrete mix with added liquid polymer. It helps the concrete bond and also helps the fake rock dry more durable and resist cracking.

  15. The polymer additive will improve durability and resist cracking, especially along seams or where the ground is shifty. The rebar backing is important also to prevent cracking. Just make sure you understand how to work with liquid polymers before you start. You might want to practice in an inconspicuous area before going whole hog.

  16. Nice blog.....In my opinion Concrete is the most widely known example of this.The new category has been proposed to recognise that man-made rocks are likely to last for long periods of Earth's future geological time, and will be important in humanity's long-term future.Rock & Concret Breaking

  17. This is amazing. I never considered how they made the habitats at zoos, etc. We are hoping to make some large, fake boulders (and maybe a cave--fingers crossed) for our back yard this summer. How warm does it need to be to have the cement cure in place? The foil for texture is genius!

  18. You can pour cement in almost any weather. I like to be able to feel my fingers and toes, just as a general rule of thumb.

  19. Mr Fixit... Thank you for this great article! I wish I'd found it a couple years ago when I first started playing with making faux rocks! But, to paraphrase your statement.... After some terrible experiments and a few happy accidents, God has decided to bless me with the knowledge you have gathered and shared so freely and generously. Thank you!!!

  20. Very good blog I am looking into making a few boulder formations for a waterfall does he have a technique for water proofing the rocks
    Thank you

  21. It's concrete. Concrete is pretty well waterproof once it's cured. You might use some concrete sealant (see your Home Depot or Lowe's)to prevent the concrete from absorbing water. Just ask the people at Home Depot.