The most important tools needed to create this fountain are a wood saw (circular or table), mortar mixer (could be a strong drill and a paddle) a strong air compressor and a stucco sprayer. Because we are professional concrete artisans at RockMill Concrete we have used some equipment that isn’t found in the common tool shed. But, don’t worry, everything we’ve done here can be done by an avid DIY’er.
The first step is to imagine your shape. I like modern designs and tend to gravitate towards stark boxy elements. Here is the initially imagined fountain concept:
The overall concept is stacked boxes with water flowing along the outside of the top box into the lower box serving as the water reservoir. Above you can see a cross-section of the setup. The red tube on the left serves as a power supply conduit for the pump within. The pump can sit on the bottom of the basin box and is plumbed to a fitting on the top box. The top box will sit on some brackets which I will explain in detail later.
After you imagine your shape, the next step is to create your mold. A non-porous material that you can cut works best to construct your mold. Make sure to choose a form board material that has a texture you like.
To create this fountain I used some particleboard leftover from another project. Using particleboard is a bit tricky because it is incredibly porous and will disintegrate if wet. It was a material on hand so we made due.
Once you have your material, cut the pieces to suit your overall size and shape. This is a large fountain; the bottom finished piece is 28.5” square and 24” tall while the top box is 22.5 square and 14” high. We’ve cut the form boards long on two sides (thickness of material x 2 + short side) to allow room to screw them to one another.
Because we used particle board, we needed to apply a wash coat with thinned-down polyurethane to all sides of each piece of particleboard. Any ‘varnish’ type coat would work. You would want to use a solvent appropriate for your varnish (in our case water) to allow the material to penetrate into the substrate. I thinned our polyurethane by half. (Plywood or any potentially porous material would require the same process.)
To ensure that the particle board was fully non-porous, after the wash coat we used standard latex paint (again something we had on hand) to coat all sides evenly so the surface doesn’t directly come into contact with the concrete. This step is to prevent moisture absorption into your forms which can destroy them and also cause concrete curing problems. We’ll be using plastic to cover everything as the concrete is setting. The humidity under the plastic can be 100% so it is very important to seal all sides of the form boards. We left the latex paint to cure for a weekend.
The next step is the mold assembly. We assembled each of our box molds and used hot glue to stick them to a flat table. If you don’t have a flat moisture resistant table then you’ll need to include a bottom on each box mold. At Rockmill we have many laminate tables which serve as work-horses so we used one to form the bottom of the two molds in this case.
After the overall mold structure is built, the next step is to create depressions for the conduit pipe on the lower box and for the water entry point on the top box. The conduit pipe will be attached to the lower box with a bulkhead fitting and we wanted to recess it up from the bottom surface. For our lower recess, we used an inverted dish with a flat bottom although there are many objects that could serve this function. There will also be a bulkhead fitting through the top box and we wanted it to be recessed from the top plane so as to keep the bulkhead from being seen. For the top box recess, we used a 3” PVC end cap.
The last step in making the mold is prepping the mold’s surface. Firstly you will want to ensure that the surface is smooth and consistent. In our case the latex paint was applied with a roller and hence a few roller lint bunnies were found here and there. These were knocked down with some 220 grit sandpaper. Sanding should be very light and fast. The goal is to remove the lint without penetrating the coating. Even with care, it’s likely that you will sand through some places. Not to worry, the wash coat step will help to keep moisture out of the wood.
Next, apply paste wax to the insides of your box molds. Almost any wax will do. You can find paste wax in the wood finishing section of a hardware store. I would choose wood wax over automotive wax if you can as I feel it leaves a thicker film, although, in a pinch, I would guess auto wax would work. We applied one coat of wax because we then applied a specialty concrete release oil. This is something we purchase in 5 gallon drums so in your case, with DYI, two more coats of wax will be in order.
After your mold is prepped it’s time to think about the concrete. We assessed that we would need two batches based upon calculating the surface area necessary to cover and our chosen thickness. We decided the first coat would be 0.2” thick. Our mold set is a whopping 47 square feet; at 0.2” thick this requires 0.85 cubic feet of material. We make our mixes from scratch, that is sand, cement, various admixes and for the face coat and PVA fiber. This fiber is something that you’re only going to find at a concrete craftsman store. It’s pretty much a requirement to use specialized concrete mix for this project as compared to something at a local box store. I won’t go into the details about this topic but here are some links to places you can purchase the good stuff:
Here’s where the stucco sprayer comes into play. This is something you can purchase at a local home center for about $80. There are also special concrete specific face coat guns but, for the money, the one from the home center is great. If the gun has different sized nozzles, outfit the largest one. We shoot face coats at about 30 PSI give or take so plumb in your air compressor and dial the pressure to that ballpark with the trigger depressed.
After doing your calculations and getting all of your mixing materials together, you are ready to mix your concrete. It is critical to not use too much water in your mix as it will decrease the strength of the finished fountain. For face coat we dose water at 30% of the total dry material. Mix up your batch thoroughly and allow the material to sit undisturbed for about 10 minutes. After 10 mins, come back to the mix and add small amounts of superplasticizer (available from the links above) to the mix until reaching a spray-able consistency. Here’s a video describing what is a good consistency:
Hopefully you have a helper on hand to help you load the sprayer’s hopper. Start with about ¼ of the hopper full as the material weight can be cumbersome, especially if it’s something new to you. Spray a test panel to ensure the material is flowing from the gun well. The video above goes over tips and what consistency you need to look for.
From here, it’s a pretty straightforward process of coating your mold with concrete. Depending on the size of your mold, you may need to reevaluate your mixture’s consistency. If it’s too thick, mix it again and add tiny amounts of superplasticizer. But, be cautious because too much superplasticizer will cause your spray mixture to run down on vertical surfaces.
Try to plan out your spraying thickness such that all of the material is used and applied evenly on the mold surface. We covered the mold using about half of the face coat batch. Then we coat it again (second face coat) with the remaining material. The time it takes for this face coat to set up (stiffen/harden) depends on many variables like the mix you’re using and the temperature of the room.
Use a chip brush or a silicone basting brush to brush after the second face coast as soon as you can to help consolidate the concrete by removing any air holes and potentially evening out the spray work. Brushing too soon will just move material around and you risk thinning areas. Brushing too late can be ineffective as the face coat is too stiff to consolidate. Keep checking the face coat every 10 minutes or so. In general, we brush after about 30 minutes but that time can vary tremendously.
Brushing provides another benefit. The surface left after brushing is slightly rough with brush lines and is perfect for bonding another layer of concrete. At this point we only have about 0.2” of material on the mold face which is pretty thin and not very strong. The next step will be to apply a “backer” mix of concrete. The backer mix contains glass fiber which provides the strength necessary for your piece to firstly de-mould but ultimately not break in use.
We can tackle the backer application a few ways. Perhaps the easiest is to let the face coats setup overnight. The advantage with this method is that the risk of poking through the face is almost null. On a difficult to reach part (such as the deep big box) It’s very likely that when reaching in and applying the backer you will scrape, poke, etc the face coat. The slight disadvantage is that a bonding agent is required between the setup face and the new material.
There are two types of bonding adhesive available for this task. One requires itself to setup and dry before applying the next coat of concrete and the other doesn’t. If you choose to apply backer the next day pick up some concrete bonding adhesive and follow the specific instructions on that product.
If you choose to apply backer immediately after face coat, be sure it’s setup enough where you can leave a slight finger depression but no more. If you wait too long, the backer could not bond properly.
Planning the backer is much like the face. You must decide the thickness desired and calculate the batch volume necessary. With the backer we will use alkali resistant (AR) glass fiber. This will be something available from the suppliers listed. We are choosing a finished part wall thickness of 0.5” and our mix calculator yields 1.2 cubic feet of material required. We will choose a slightly lower water content at 28% of dry materials and choose a glass fiber amount of 3% of total batch weight.
Just like the face coat, thoroughly mix your batch with the water and allow it to sit for about 10 minutes. Now apply superplasticizer until the mix work-ability improves. Only after the right consistency is achieved do you add the AR fiber. AR fiber is brittle and you want to mix it into the concrete gently and as the last step.
We used a different gun for this application that I don’t expect the non-professional to have Fancy backer spray gun. The consistency we need is dictated by how the material flows out of the manufactures provided funnel. We add plasticizer in small amounts until the correct consistency is achieved.
You can still apply backer to your face coat by carefully regulating your mix consistency and using a mortar trowel. To hand apply the backer make your mix loose enough that you can apply it to the sides without it slumping down and not so stiff that you can’t spread it. When hand applying, be careful to not over or under apply material, pull some material away in places and use a gauge block of the desired thickness to inspect your progress.
Here’s a video of us spraying the backer coat to the walls.
Like the face coat, this backer will be hand brushed to help press it to the face coat and reduce voids. Brushing the face coat was important for the aesthetics of the fountain and brushing the backer coat is critical to the strength as it’s only half an inch thick.
Follow the instructions for curing time with the craftsman concrete mix you are using. When we made our fountain the shop temp allowed us to demold it the next day. Demolding is straightforward; unscrew the form boards and gently pry your concrete out from the walls. Hopefully your waxing was thorough and you have some pretty parts to look at!
We wanted a as molded finish to our fountain so we simply cleaned the part faces with soapy water and a scrub pad. We applied a concrete sealer and assembled the pump, tubing, brackets and bulkheads. Here is our finished product:
I hope this served as some inspiration for you and given you some insight into the steps involved if you are venturous enough to take this on as a DIY project.