How to Fix Cracks in a Kool Deck

Hunker may earn compensation through affiliate links in this story.

Things You'll Need

  • Garden hose with nozzle

  • Eye goggles

  • Rubber gloves

  • Protective clothing

  • Face mask

  • Scrub brush

  • Muriatic acid

  • Water

  • Plastic buckets

  • PTA bonder

  • Kool Deck cement

  • Clean wooden stick

  • Applicator

  • Drill with paddle

  • Cloths or towels

  • Trowel

  • Plastic sheet

  • Sand


Wash the newly-repaired area daily over the following six weeks to help strengthen the patch.


Muriatic acid is very dangerous, with a strong odor that can burn sensitive skin and nose and eye membranes. Keep baking soda nearby when applying in case of an accidental spill.

Image Credit: Garden Hose image by Richard McGuirk from <a href=''></a>

The Mortex Keystone Kool deck system is a colored cement topping used most often near pools and patio areas to keep the cement surface cooler in temperature and to provide easy cleaning for your deck. Although Kool Deck systems provide improved expansion and contraction of surface elements over regular cement, they can still crack over time and require repairs. You can fix cracks in your Kool Deck with the aid of a Kool Deck patch kit, available through the Mortex Corp.

Step 1

Clean the surface of your Kool Deck with a garden hose power nozzle to remove dirt and loose cement from the area. Any deteriorated concrete should be removed from the area of repair before attempting to patch.

Step 2

Soak the repair site in addition to the entire area surrounding the damage with plain water.

Step 3

Wear rubber gloves, goggles, a face mask and protective clothing while preparing muriatic acid. Prepare a solution of one part muriatic acid to one part water in a plastic bucket or container. Always add the muriatic acid after the water to avoid splashing of the caustic substance in the bucket.

Step 4

Apply the muriatic acid to the area of damage with a scrub brush. Allow the solution to bubble for several minutes before scrubbing and rinsing the area thoroughly with clean water. Be sure the area is free from the acid before filling the cracks. Keep the area wet until you are ready to apply the bonder.

Step 5

Mix two parts of the PTA bonder to one part water in the following manner: add one half of the water needed to the PTA bonder in a quart-sized pail. Stir the bonder thoroughly for two minutes using a stir stick. Let the mixture stand for three minutes, during which time you can prepare the Kool Deck mix.

Step 6

Put the Kool Deck cement mix into a second pail. Add 24 oz. of water to the cement mix, constantly stirring as you add the water. Use a drill with a paddle to stir the mixture until it is blended smoothly.

Step 7

Add the remaining water to the PTA bonder, stirring until it is completely blended. Soak the entire area you will be patching with water, blotting up any excess pooling with a towel.

Step 8

Use the provided applicator to scrub on a thin coat of the PTA bonder over the area that is cracked. Wipe up any excess bonder that may get on the outside area of the repair with a wet cloth.

Step 9

Rinse the applicator completely before using it for the Kool Deck cement mixture. The bonder and the cement should never mix on the applicator.

Step 10

Apply the Kool Deck cement before the bonder has dried on the crack. Pour the Kool Deck cement over the bonder into the crack, adding additional cement with the applicator to form high peaks over the crack before it begins to lose its sheen.

Step 11

Trowel the Kool Deck cement after the water sheen dissipates on the cement, using light pressure to flatten any high points on the first pass of the tool over the cement. Wait several minutes and make a second pass over the area to smooth the cement.

Step 12

Clean off any residual cement or oversplash while it is still wet around the surrounding patch; after drying, it may be impossible to remove.

Step 13

Cover the patch with plastic as soon as you finish the repair, weighting it with sand and keeping the plastic sheet on top of the repair for 48 hours.

Step 14

Clean the area after two days with water and a stiff scrub brush and water. This will help keep mineral deposits from forming over the area of repair.

references & resources

Abaigeal Quinn

Abaigeal Quinn works as an international entertainment broker in the United States. She is a former news editor and insurance agent who began writing for a daily newspaper in 1995.