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Chris Sullivan

This stamped concrete patio is flaking away due to a surface layer of weak concrete.


I hope you can give me some idea about what's going on with my concrete pool deck. The deck was poured in August 2005 by a local contractor, who then stamped the concrete in an Ashlar slate pattern using a dry color release. After he washed off the residual dry color from the surface, the deck did not look evenly colored. Some areas had barely any color while others had too much. I told the contractor that the color was unacceptable and needed to be fixed before the sealing. Despite that, when I wasn't home the contractor went ahead and applied a sealer pigmented with a dark brown stain. That made the deck look even worse, but it isn't my biggest problem. After the first winter, which was mild for the central Midwest, the decorative surface of the deck started to peel and chip away. In some large areas, the surface came off completely, down to the aggregate. I did not apply deicing salts, and no water was left lying on the surface.

Length: 06:08
Watch this easy-to-understand explanation of what causes concrete spalling, from concrete expert Chris Sullivan.

Length: 05:17
Watch this easy-to-understand explanation on repairing spalled concrete, from concrete expert Chris Sullivan.


Unfortunately, you have a slab of decorative concrete that's in bad shape and beyond easy repair. As the photo clearly illustrates, the top 1/2 to 1 inch of the concrete surface is beginning to come off because the stone, which gives concrete its strength, is pushed down, leaving a weak sandy layer on top. Once the top surface has been breached, it's just a matter of time before the entire top will break apart. Because the layer below with the stone showing appears to be strong and intact, you have two repair options: totally rip out and replace the slab or remove the top 1 inch and cover the underlying concrete with a stamped overlay.

In my opinion, the problem is not caused by the contractor's coloring methods. Instead, it's probably due to poor installation techniques, poor curing, a bad concrete mix or a combination of all three. Stamping the surface of bad concrete only speeds up the deterioration process. What makes things worse is that the contractor is refusing to take any responsibility and will not get involved to help figure out what happened.

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Author Chris Sullivan, technical expert and vice president of sales and marketing for ChemSystems Inc.

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