How to Repair Granite Cracks

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How to Repair Granite Cracks

According to the American Society for Testing and Materials (ASTM), granite is a "visibly granular, igneous rock" that can appear in myriad colour combinations. The stone typically contains quartz and feldspar, as well as one or more dark granular minerals. Granite may also include minerals, such as mica and hornblende. Considered one of the most durable stones, granite has applications for artists, architects, and interior designers. However, even the strongest granite can crack, which requires do-it-yourselfers to repair it. Homeowners and construction workers should learn about what causes granite to crack, as well as follow a few steps to repair the cracks.

What Causes Granite to Crack?

The appearance of very narrow fissures is the first indication of cracking granite on a bathroom countertop or large fountain sculpture. At less than a centimetre, granite cracks can be hard to detect with the naked eye. Although vandalism plays a role in producing cracked granite, the cracks caused by human destruction are typically much wider than inherent and human-induced causes. Some of the inherent and human-induced causes include structural overloading, the use of hard mortar mix, flaws within materials, and salt migration caused by prolonged moisture exposure. Thin fissures demonstrate the potential for the granite to become structurally unsound, which means do-it-yourselfers must address the cracking by performing immediate repairs.

Repairing Granite Cracks

In addition to creating potential structural problems, cracked granite also diminishes the beauty of the stone. The loss of aesthetic appearance undermines the value of the granite, which can hurt homeowners who place their home on the market or reduce the value of commercial property because of unsightly exterior flaws. Construction workers and homeowners can repair cracked granite by assembling materials, buying a granite repair kit, and following a few repair steps.


The efficient repair of granite cracks begins with the assembly of a few materials and the purchase of a granite repair kit that matches the colour of the cracked granite. Construction workers may require the use of ladders to access hard-to-reach cracked granite sections of tall office buildings. The materials that do-it-yourselfers need to perform a successful repair job include granite cleaner, a soft cloth, masking tape, and a razor blade.

Granite Cleaner

The first step for repairing granite cracks involves carefully spraying granite cleaner on, and about 1 cm around, the cracks. Seasoned professionals can pour the granite cleaner, but pouring the cleaner requires a steady hand. Spraying ensures the cleaner finds its way down the fissures. Do-it-yourselfers can force the cleaner into the cracked portion of the granite by using a soft cloth that also removes surrounding dirt and debris. After applying the granite cleaner, homeowners and construction workers should buff the entire area to prepare for the next step.

Masking Tape

Run pieces of masking tape along both sides of every granite crack. Masking tape serves two purposes during the repair project. It outlines the location of each crack, which is important for very thin fissures that appear on small sections of granite, such as tile. Second, masking tape ensures a quick and easy cleanup of the repair epoxy. Do-it-yourselfers may need to tear more than one piece of masking tape to run along the sides of larger cracks.

Epoxy Compound

The third step of the repair project requires do-it-yourselfers to mix the two-part epoxy compound with the colourant in an enclosed repair kit tray. The colourant should closely match the colour of the granite near the cracked portion of the stone. If the cracked area includes multiple colours, homeowners and construction workers should chose the dominant colour.

Apply Repair Compound

With the use of a small putty knife, apply a small amount of repair compound by pressing the putty knife deep into the fissure. Do-it-yourselfers should move the putty knife on both sides of the crack at different angles until the compound completely fills the crack. They may experience compound that slumps down, which requires granite repair workers to add more compound until it rises to meet the granite surface.

Razor Blade

The compound needs to dry for about 10 minutes, although the time to harden varies between hot exterior walls and moisture-laden interior rooms. After the compound hardens, do-it-yourselfers run a sharp razor blade to remove excess compound until the crack becomes smooth to the touch. Once the crack reaches the proper level of smoothness, remove the masking tape and do not use the repaired cracked section of granite for at least 24 hours.

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