In nature, every rock formation tells a story. Boulders shift, erode and experience alterations in color over time. When installing artificial rock, professionals must ensure that the tale is realistic, compelling and intuitive. An average viewer should be able to see, for instance, that one formation fell against another causing a third to crack.
The first step in mastering the design and construction of non-natural installations lies in the ability to properly address scale. Formations should be large enough to mimic nature without overwhelming the space, and configured as a grouping of boulders or a cliff face that predates the home. It’s recommended that installers work with larger pieces rather than stacking smaller ones because the latter creates the sense that the formation was deposited there by a crane, which detracts from the realism.
Conversely, installers must avoid creating one massive structure that emerges unrealistically from the ground like a dome.
In nature, sections of rock split and separate over time. Those using hand-sculpting methodology must form these discrete specimens from the monolithic piece of concrete so they appear as individually created rocks.
To achieve this effect, place a gap measuring at least a couple of inches between individual stones. Contiguous rocks should not be flush with one another, with some protruding 3, 4 or even 5 inches from adjacent sections. Take the same care where the rockwork meets the bond beam.
The cleavage between the stones also needs to be deep so that the bottom of the gap is invisible. This means that, rather than attempting to conserve concrete, installers must shoot enough material to allow proper carving of all crevices.
Finally, it is important to generate a sense of visual excitement by utilizing twists and turns. Showcasing the rock in various stages of degradation reinforces the illusion that it is an evolving entity.
Perhaps the most essential aspect of crafting effective non-natural rock formations is achieving mastery of how they are formed.
In nature, smaller pieces of rock, or “talus,” crack off over time and fall to the floor below a larger formation. Talus generally occurs when two substantial cracks intersect, leaving a weakened section.
To emphasize this phenomenon, it’s important to showcase the cracks that caused the breakage. The talus, and the accompanying void left behind, should have near-identical surface types, so one can imagine the two fitting together like a puzzle.
Installers also can design a rift in progress by creating a large split within a specific rock. This shows the degradation of the mass.
To mimic aging in artificial granite, some artists simulate an effect called exfoliate plates, in which large chunks of rock, measuring from 1- to 6 inches thick and 3- or 4 feet in diameter protrude from the formation. When occurring naturally, these outcropppings eventually fall from the parent formation as a result of snow and frozen rainwater accumulating beneath them.
To achieve exfoliate plates in an artificial setting, drop a bucket full of plaster or concrete on the formation and, shortly before the material hardens, form pocks with a fillet knife or trowel so that they are almost completely detachable. This creates the illusion that one could place their fingers underneath the plate and lift it off.
It’s important not to underscore the entire perimeter because part of it must still appear attached.