As a place for birds to drink and bathe, a birdbath attracts species to your yard that feeders and houses won't attract. With simple tools and materials, you can build a concrete birdbath without any previous experience working with concrete. Place birdbaths directly on the ground, on secure pedestals or on logs.
Choose a flat, level place to work. Spread a sheet of heavy-duty plastic to protect the work surface. Choose a location protected from rain and freezing temperatures -- ideally warmer than 60 degrees Fahrenheit -- where you can leave the birdbath undisturbed for a week while the concrete cures.
Pour a pile of play sand onto the plastic sheet and moisten the sand with water so it holds together. Firmly pack the sand into a mound in the size and shape you desire for the interior of the birdbath’s bowl. The mound of sand acts as a mold to cast the concrete over. Keep the depth of the bowl relatively shallow; birds prefer baths that are less than a couple of inches deep.
Cut a sheet of plastic slightly larger than the mound of sand and coat one side of the plastic sheet with petroleum jelly or motor oil to keep the concrete from sticking to the plastic. Place the plastic sheet over the mound of sand with the oiled side facing up. As an alternative, you can cast the concrete directly over the sand, but it will give the finished concrete a rougher texture.
Mix 3 parts contractor’s sand and 1 part Portland cement in a large metal or plastic bucket using a mason’s trowel or garden trowel. Add water to the mixture in small amounts, stirring thoroughly before adding more water. Stop adding water when the mixture is the consistency of modeling clay. Squeeze a handful of the concrete to test it. If water drips from your hand, the mixture is too wet and you need to add a bit more sand and cement in the same proportions. Wear gloves, eye protection and a dust mask when handling cement and wet concrete.
Cover the plastic-wrapped mound of sand with a 1/2-inch-thick layer of the concrete mixture using a trowel. Pack the concrete down firmly over the mound of sand. Cut strips of plastic drywall reinforcing mesh, or 1/4-inch metal hardware cloth for larger birdbaths, and lay the strips over the concrete. Trim the mesh or hardware cloth back slightly from the edges of the bowl so no mesh protrudes beyond the edges of the concrete.
Cover the mesh with another 1/2-inch-thick layer of the concrete mixture and smooth the surface with a trowel. For birdbaths wider than 16 inches, add another 1/2-inch-thick layer of concrete.
Drape a sheet of plastic loosely over the concrete and weigh the plastic down around the edges. Let the concrete sit undisturbed for one week to allow it to cure fully. To attain maximum strength, concrete needs to stay damp while it cures. Check the concrete every day or every other day to ensure it does not dry out. If it appears dry, spray water over the concrete and re-cover it with plastic.
Pick the concrete birdbath up off the sand mound and turn it over carefully. Peel both plastic sheets off the concrete. Ensure that the concrete surface is dry. Leave the concrete unpainted or apply latex wall paint with a paintbrush to give the birdbath some color and a smoother surface. Seal the birdbath by applying a water-based concrete sealer directly on the finished concrete or over the latex paint.