Concrete spheres make an intriguing and mysterious garden ornament.
They can be created with an exercise ball or other inflatable ball. Just wrap layers of chicken wire, hardware cloth or metal lath and smeare with thin layers of mortar as you go. You can see my favorite decorative concrete mix “here” and how to mix it “here”.
It is very difficult to cover the entire ball with the full steel layers. The trick is to use smaller overlapping strips. Apply the strips to just part of the ball and then smear with mortar. after it sets up enough to hold shape you can turn the ball a bit and continue with the process until the whole thing is covered.
You can leave a hole of any size or shape for different purposes.
1) Purchase a sphere mold. They come in halves which are intended to be poured and mortared together to create a solid concrete sphere.
Foam shapes can be cutout and placed against the ball and between the steel strips then removed after the concrete is cured to create shapes.
I won’t go into detail here on texturing and hanging (applying) or staining the concrete because it’s all been covered in detail on the other pages of the Stone Craft section of this site found on the top left menu.
The construction of my hollow sphere birdhouses is always a puzzling mystery to people. It was something I wanted to make a variety of with different textures, designs and finishes. The inflatable ball method was too time consuming to be practical and nearly impossible on such a small sphere so I invented a new way which I’ve kept a well gaurded secret until now. I'll get pictures of the steps up when I get the chance.
Here is the process:
2) Use a strong container with a bit of size to it, a heavy duty nursery pot works well. And make a reverse mold of the outside of the half ball sunk into the container. after it sets up, remove the mold and allow it to completely cure. If you intend to make more than one sphere it’s well worth it to make at least two of theses. You will only need one that's heavy duty the rest can be lightweight as they will just be used for forms.
3) Use a piece of metal lath and work it into the newly made heavy duty concrete mold. Tap it in with a rubber mallet and a wooden rod stretching and bending it into shape.
4) Pop out the metal lath half sphere and clean it up with tin snips then repeat the process for the second half of the sphere.
5) Lay some plastic wrap or thin plastic in the mold to act as a release agent. You will be placing the metal lath half sphere back into the mold on the plastic to use as a form.
To make the bird hole, use a short piece of pvc pipe in the desired hole size. Cut half of the pipe size out of each half of the sphere.
Now you can place your metal lath half spheres into the forms.
6) Smear in just enough mortar to cover the metal lath and clean up the half hole cutout you made for the pipe to go.
7) Once the mortar has set up enough to be removed without breaking, carefully remove the halves from their forms. It doesn’t have to be fully cure, just enough to remove it without breaking.
8) Now place the two halves together. Using a weather-proof wire, carefully wrap the two halves together. Twist a hanging loop in the wire and continue it around the sphere a ways to be embedded in the concrete. The hanging loop needs to be large enough so that it won’t be buried in the ¼” or so layer of texture coat. Also pay careful attention to the exact placement of the loop as it will determine the exact placement of the hole when the house hangs.
9) Hang your sphere by it’s new hanging loop and Insert your piece of pvc pipe at a bit of a downward angle to prevent water from running into the completed house. Coat the outside with mortar giving it your own one of a kind texture.
10) Be sure to properly cure your sphere for maximum strength and durability. As the concrete begins to kick over carefully twist the pipe to keep it from bonding to the mortar. Once it's safe to do so gently twist out and remove the pipe.
11) Before coloring the completed and fully cured sphere, use a small masonry bit and drill a few drain holes in the bottom side.
12) Be sure to hang your house in a location shaded from the hot afternoon sun.
Mirror Your Sphere!