Hypertufa "How To" Tips – Using Armatures & Forms for Larger Projects

Questions About How To Construct
A Hypertufa Rock Formation For A Waterfall

I received an email from an enthusiastic hobbyist who wrote:

Hello, first of all let me say thank you very much for such a great and informative site! I’m writing because I need to get some of your hypertufa how-to advice.

I am making a waterfall with either hypertufa or concrete and I wanted to make a rock-face resembling a cliff. I have been looking at some nice concrete trees and cliffs but I’m seeing a lot of welding and rebar – I realize that’s important for large structures.

My structure is just over 1 meter tall, and under half a meter wide, and I want to make it as light as possible. There will be a waterfall. The biggest issue is that I really want the entire structure to be hollow.

I think I might use some wood/bamboo/styrofoam/chickenwire combination as an armature. I know I have to cover it with the wire mesh cloth strips. What I don’t know is if I can remove the armature after the first stages of curing?

Am I supposed to cover the entire armature with plastic and a release agent before I put on the wire mesh? But if I am wire-tying the mesh onto the armature, would I have to untie it before removing it or is it supposed to be permanent? It would sure make a lot more weight and mass, and would make the structure very ugly if seen from the bottom.

The good part about this particular waterfall is the back will be against a wall, so could I just leave it a half shape form in a trough style, and then lift it up on its side? and then could I later cement that waterfall to a base? The base will extend about 1.5 meters beyond the front, so I would prefer to make it all upright from the beginning.

So that’s my question – can it be done upright and can the armature be removed afterwards? And any ideas as to the best armature material? I would prefer not to weld.

I saw some beautiful indoor waterfalls with welding of wires thinner than rebar, used in conjuction with something like chickenwire, and I could see it was mostly hollow. I didn’t see any other filling other than wire mesh beneath it … but I don’t undertstand how they removed the filling afterwards, or how they made this big hollow rock face.

I kind of guess that it’s hollow because they’ve removed the form, but it could be that the wires are really secured well, but I still don’t see how they could form it through the chickenwire, keeping the chickenwire hollow.

One more quick question, can it be used as a waterfall before the 1 month curing process? Say after a week?

I would greatly appreciate any knowledge or how-to tips on this subject, or a point in the right direction. I am very interested in making large hollow hypertufa and concrete rock structures for waterfalls in the future as well.

Thank you! “Chinarabbit”

My reply:

Hi Chinarabbit:
I hope I can answer all your questions. And thanks for the kind comments about my website – I appreciate that. 🙂

Whew … I give you credit for taking on a large project like what this one will probably be. You have pretty much answered your own questions, in that there has GOT to be some sort of inner structure onto which you will apply the hypertufa or ‘crete. Whether it is a welded rebar frame (yes … I understand most of us just don’t have this option, due to not having the welding equipment and/or the money to afford to have one made for us), or a chicken wire contraption such as you described … based on what you want to do, and to have it LAST A LONG TIME you will apply the mixture to the frame.

I will highly suggest that the frame NOT be removed, as it will be an integral part of the final object.

Now … on a side note, though I really don’t have a 100% complete idea of what you want to do … the “inner structure” could be nothing more than chicken wire. If you wad up plastic (bags) and fill the entire inner cavity of the form with it, the “wads” would act as a temporary barrier to keep the wet mixture from falling through the chicken wire. When partially cured, the plastic wads would be removed, thusly what you have is a reinforced ‘tufa or concrete structure. Follow me here? And you are making the entire structure lighter in weight, which is also one of your concerns.

I am guessing chicken wire is going to be an integral part of the inner structure, in order to get a curved surface.

In addition, you’d better use a reinforcing agent of some sort to make a more durable recipe. Again … longer lasting for you.

And lastly, DO NOT RUSH the curing process! (30-days is about what it needs to be.) That is one of the biggest reasons for failures! Plus, if plants and more importantly fish are going to be in your pond … you have GOT to leach out the lime from the cured structure.

I hope this helps some. Post more if I’ve not clarified anything enough for you. Let us know how your project progresses! Good luck!

~~~

Chinarabbit replied:

Thanks for your time and response, it’s been very useful. I am ready to get started!

I have already bought several large styrofoam sheets of different thicknesses and a lot of bamboo skewers. I thought I’d follow this procedure:

1. just carve the basic shape I need with the styrofoam, securing the pieces together with the bamboo skewers, making a solid structure, because I’ve decided to leave the back open, and just have a sort of half-shape with a rock face and an open back and bottom on the finished product. Actually there will be 2 rock walls, at opposite ends of the structure, with their back to a plywood wall, and a concrete riverbed/planter/pond along the bottom connecting the two.

2. wrap the structure in large plastic bags for release (maybe even some vegetable/mineral oil mix on top of the plastic, or is it unnecessary if I have plastic?)

3. wrap that it in a chicken wire frame…

4. put fine wire mesh strips over the chicken frame (do you think this is important? or can i do without it? I thought the fine wire mesh might make the concrete more stable, but it would also make the chicken wire unattached to the concrete, perhaps the chicken wire would fall away because it didn’t penetrate the fine mesh?)

5. mix the concrete and apply a layer 3 inches thick and carve out the shape of rocks. can you recommend a replacement for the fiber strands? I’m an American living in China and not sure i will be able to find those, can they be made from something else?

6. after it begins curing I would remove the styrofoam, leaving only the wire mesh/chicken wire attached beneath.

7. keep misting it. This project will be behind glass, and include an automatic sprinkling system, maybe I will just install the glass and let the sprinklers mist it for a month.

So, I have those minor issues. Thank you Claudia for your in-depth responses. I would greatly appreciate your final input on these last little details.

Once again they are:

A. what do you think of the styrofoam form leaving a half-shape waterfall?

B. is oil useful on plastic?

C. wire mesh on top of chicken wire? or just one or the other?

D. replacement reinforcer other than the strands you mention in your site.

E. also, should I apply a layer of concrete/Elmer’s glue mixture to get finer detail? Or is one layer sufficient for waterfall detail? And would the outer layer weaken the structure?

I have seen several other forms, such as overhead tree branches, which have had an outer layer applied and also seems to fall off exactly at the seam between the two layers, who knows if they used any glue. Probably not, it’s in China and I don’t think they’ve read your site. lol

So anyway, thanks again for all help and ideas. Your The-Artistic-Garden.com is by far the best website on hypertufa how-tos that I have found.

You are a very generous person to offer such wonderful advice in the spirit of helping and giving and sharing. So many other sites on this subject regard it as quite an expensive little secret of sorts. I’ve recommended your site to all my family and friends interested in gardening.

Keep it up – I hope it’s a permanent site that will last for years to come.

~~~

I replied again:
Hi Chinarabbit:

Wow, you live in China! I just love the internet – such an incredible way to meet people from all over the world.

OK, you are keeping me busy here.  😀  Let me try to answer everything:

A. Styrofoam can be a great sub-surface or inner form that can be completely covered in ‘tufa … so this sounds OK;

B. Nope — don’t need the oil. The plastic should just pull away from the ‘tufa;

C. I “think” (I am using my best judgement here–but it is ultimately up to you!!) the chicken wire, mooshed inbetween the ‘tufa will be just fine — no need for the mesh strips;

D. You can use a bonding agent (read more here: hypertufa & concrete bonding agents explained) to strengthen as opposed to the fibers;

E. 1st Q answered by “D”; I cannot accurately guide you if one layer will be enough — you did say 3-inches — that should be fine, but again, I am not there along side you 😉 perhaps the layer on the branches were not properly prepped before whatever was applied to them (you’ve not mentioned?), thusly the material is falling off. It isn’t adhereing to the sub-surface properly.

I hope I answered everything. Umm … one thought that I must mention that jumped out at me. You mentioned a plywood wall behind this new structure? I am going to assume you know constant moisture and/or direct contact with water is NOT a good thing for plywood. I am hesitant of you using plywood with a waterfall construction.

And, thank you so very much for your kind compliments. It means a lot to me that people do appreciate the attention I try to put into everything I write and share online.

Good luck with this project and I do hope all my “hypertufa how-to” tips have helped steer you in the right direction.

Comments

  1. Hi! What a wonderful blog, I wish I had stumbled across this sooner! Very timely, too. I’ve been researching how to create some false ancient ruins for my wooded back lot (sort of like what you might see in the Lord of the Rings movies), but on a much smaller scale. I was thinking of a sitting area that looks like a small portion of a ruined castle wall, or perhaps an area with a few fallen column bases and half columns laying in the undergrowth, that sort of thing. Have you ever seen hypertufa used in that way?
    Cheers!
    Gregor, the gardening goth.

  2. Hello,
    My father and I built a waterfall and pond around 1980 in SoCal. We did this over a few years on the weekends. The beautiful almond color layered boulders at the bottom 4 foot base became unavailable so the upper 3 feet is a mixture of rock. I don’t like the look and would like to cover the upper section with concrete a sculpt it to match the base and somewhat redirect the water flow for a more dramatic aesthetic effect. I am only physically able to do a few hours work per day. My concerns are:
    1. Any issues like separation, cracks… with doing small sections over time, maybe months.
    2. Any reinforcing required with the reface/covering that may vary from 1/2″ to 15″ thick ?
    3. What type of cement is best ?
    4. What is your recommended mixture of materials ?
    5. What paint or dyes for tinting a variegated almond, grey and charcoal.
    6. For fine tuning the water flow, what would be the minimum and maximum thickness ?
    7. For fill and shape backing are aluminum plates, bars and Styrofoam acceptable ?
    8. I have confidence in my sculpting, detailing and color matching but totally unsure about the materials, application and their limitations.
    Your suggestions would be greatly appreciated.
    Thank you

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