How to Make Gunite Look Like Stone

Geology

• Find out how the stones you want to imitate appear in nature. Natural stone is weathered, uneven and varicolored. Try to stick with just one type of natural stone. Sandstones and limestones are the easiest to create because of their smooth texture and uniform color relative to rocks such as granites.

Surface Preparation

• A thorough cleaning of the surface on which you will spray the gunite is essential. All ingrained dirt and debris has to be removed. The surface must also be wet prior to gunite application. The most efficient method is to use the compressed air and water supply of the gunite machine and spray the surface carefully. Ensure, of course, that the gunite machine’s rotary mixer is not connected at this time.

Spraying Procedure

• Once the surface is prepared, the nozzle man who operates the gunite machine signals for the cement and sand to be fed into the system. He sprays the gunite by holding the machine’s nozzle at right angles to the surface. The nozzle may be between three and 45 feet away from the surface depending on the job. In most domestic decorating jobs, the nozzle distance may only be one to two feet away from the surface. The air and water feeds must be adjusted so that the gunite glistens as it settles on the surface. An experienced nozzle man will be familiar with such adjustments.

Curing

• Similar to all versions of concrete, gunite shrinks as it dries. The shrinkage will not be as obvious or as great as in a concrete pathway since gunite surfaces are thin by comparison. The standard method of curing is to apply a fine spray of water as the surface sets. This should be done four times a day for at least a week. Some gunite contractors allow between 10 and 28 days for curing.

Texturing and Coloring

• Textures and patterns can be sculpted onto the curing gunite with a trowel to produce a stratification effect. Make sure that the layers are slightly uneven so that they resemble nature. A natural sponge dipped onto the curing gunite surface introduces pock marks that resemble water weathering. Gunite coloring is a skilled job. An experienced contractor applies a staining agent mixed with marble dust for a realistic color effect.

Sealing

• Gunite is not water-resistant and a carefully constructed natural stone pattern may disintegrate with excess moisture. Seal the imitation stone by brushing a standard domestic, nontoxic water-based stone sealant over the surface after the gunite is well cured.