Large Concrete Faux Rock Stepping Stones – How to Make Them?

How to Make Super-Large Concrete Stepping Stones for a Walkway

Judy V. emailed the other day and asked:

While I have made hypertufas and concrete leaf castings with great success I am about to try faux rock concrete slabs [stepping stones] for use in a walkway. Some of these will be close to 4 feet in width so I will have to make them in place. I am planning on them being 3 to 4 inches in thickness and will use 4″ x 4″ wire mesh used in concrete patios for added strength.

My question is about curing these concrete slabs properly. Water will leech out into the soil. I’d thought about putting plastic as a barrier between the soil and the cement but I am afraid it will trap moisture in the winter and cause heaving. Any suggestions?

I’d planned to cover the top of the “stone slab” with plastic sheeting. Since I plan to do some “carving” and also “stamp” the surface I am not sure I want the plastic to touch the top of the stone so I’d planned to keep the plastic an inch or so above the surface. Also would you suggest I use the special fiberglass fibers in the mix and/or concrete adhesive?

Any suggestions you might have would be appreciated. This is a front walkway and it is not the most used entrance into the home.

Thank you in advance.

Judy V.

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My reply:
Hi Judy:

You sound like you’re on the right track as far as the construction method. Since you’re doing such large (HEAVY!) concrete stepping stones, I doubt you will want to place plastic under them – how would you remove it? Unless you trim away the edges of any exposed plastic after everything has cured. That could be an option – just leave the plastic where it is. Certainly shouldn’t hurt anything, though yes perhaps some moisture might get trapped.

(Don’t forget to review all the how-tos on my website about hypertufa. Here’s the page for a recipe for super strong faux rocks, including really big ones: Faux Rock Recipe.)

However, you can also pour them without the plastic right into the soil – think about it. Sidewalks and driveways are poured like this. Only thing is some aggregate stone is placed as the first layer before the ‘crete is poured. This might be an option for you too – but perhaps use a layer of small pebble-type stones.

Any additional reinforcing agent would be a good idea, even though you’re using an inner layer of wire mesh within each of the stepping stones. Just know using the fibers will require a blow-torch to singe off all the little fibers that will probably stick out from the ‘crete.

I’d encourage you to practice making one big slab [stone]; make a record of the exact recipe ratios you used; let it cure for a few weeks to see what happens and by then you ought to have an idea if it’ll make it long-term and how to tackle the entire project.

Best of luck with all your projects and do not hesitate to contact me again if the need arises.

Comments

  1. How is the step making project going? We are thinking of making steps up to four feet wide and seven inches deep. Any ideas?

  2. Your advice is excellent because placing plastic under stepping stones is generally not a good idea…….unless a layer of sand is placed on plastic first.
    Concrete gains it strength by water mixing chemically with the cement, not by drying as most people surmise. Concrete requires more water in the mix than is necessay in order to maintain its workability and any moisture in excess of that amount is given off in the form of either absorbation into the the substrate (soil) or by evaporation from the top surface, which, if the fresh concrete is still in its ‘plastic’ state and has not gained enough strength to withstand the shrinkage stresses, could result in a surface looking like a checker board road map.
    With a plastic barrier placed under the stepping stone all of the excess water with be forced to leave the concrete from the exposed top surface.
    Glass fibers will definitely be helpful as they tend to keep the concrete from shrinking too rapidly as the concrete is going through its chemical hydrating process but if the excess water leaves the product prior to the concrete attaining the required strength that is sufficient enough to withstand the shrinkage stress at the upper surface, quite often cracks much like those in a bed of clay in the desert would look when drying out after a rainstorm. This is caused by water leaving (shrinking) mostly from the top surface while the lower surface maintains its mass because the water hasn’t been evoproated into the atmosphere, like that which is exposed to the effects of the sun.
    Also, removing any exposed fibers by burning with a torch works great—– if the fibers are made with polyproplene —–but if they were actually made with fiberglass it’s much more difficult.

  3. Suzanne says:

    Thanks for sharing this – my husband and I have a limited budget and can’t afford buying the kind of extra large stones we’d love to have installed on our patio. So we just might give this project a try. I’ll do a test run like you suggest in most of your hypertufa posts – to make sure we know what we’re doing. 🙂

  4. Claudia says:

    You’re welcome! I do hope these tips give you an option to affordably get the patio of your dreams. Good luck!

  5. Adellaf Eutslery says:

    I’m very glad that I found your site and this post in particular. I have been wanting to add some large stepping stones to a pathway through my back garden which is long and I have planted many shade loving plants. I don’t have a lot of money to buy the pavers, and this project would also allow me to make ones that have a more rustic look to them. I want moss to be able to grown on the edges, with time, to make the stepping stones look like they’ve been there forever. Thank you for being so sharing.

  6. Adellaf:
    I’m glad my information will help you with this project. Good luck!

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