Two years ago, a woman called to have her patio resealed. But once I saw it, I realized the 10-year-old stamped concrete amenity needed much more work. Other than when it was installed, the slab had never been sealed and appeared quite chalky.
Having settled drastically over the years, the patio had recently been raised. The holes the mud-jacking company drilled were filled with a bright white patching compound that contrasted sharply with the almost-black slab.
The slab was intended to be light gray with dark gray antiqued highlights, but the contractor hadn’t properly removed enough of the charcoal-colored antiquing release agent. He just hosed off the loose release agent and then sealed the rest of it in. Because dark colors absorb sunlight, the homeowners couldn't use the patio during the day because the surface literally burned their feet.
Added to the color and settling problems, the slab also had cracks ranging from ¼-inch to ¾-inch-wide throughout.
There were wide gaps around the perimeter where the expansion joint material had rotted out. They were unsightly and rainwater entering them would quickly cause the slab to sink again.
They needed to be filled.
I told the homeowner I couldn’t in good faith simply reseal what she had. It would certainly be shinier, but her patio would still look horrible and I didn’t want my name attached to it.
When I said all the problems could be remedied without removing the concrete, she was incredulous. She’d lived with them for several years and had become resigned to accepting the patio, warts and all. But since I couldn’t make it look any worse, she was happy to give it a shot.
Averting future slab damage
The first task was to find out what I was dealing with. I cleaned the slab with a 3,000 psi pressure washer to remove remaining antiquing release agent as well as dirt.
After the slab dried, I forced foam backer rod into the cracks and gaps and applied Sika Corp.’s self-leveling Sikaflex 1 cSL polyurethane caulk to the rod.
I chose this product for its elasticity and adhesive characteristics. Because concrete expands and contracts during periods of temperature fluctuation, rigid patch materials often crack and flake out of repaired cracks. Flexible caulk works perfectly because it moves with the concrete without being compromised.
I sprinkled dry sand generously over the wet caulk to give it texture and allow for a subsequent coating to adhere. I removed excess sand with a leaf blower.
Formulating the right surface color
When the caulk had dried sufficiently, I mixed up a very light gray homemade stain using color hardener and acrylic bonding admixture using the procedure I detailed in the March issue. The stain was applied in two coats and allowed to dry overnight. The opaque stain covered both the mud-jacking patch material and sand-impregnated caulk, producing a uniform light gray color.
As soon as the stain had completely dried, I applied Butterfield Color’s Perma-Tique powder in Storm Gray (PT12). When mixed with water and applied to a stamped slab, the product runs off high spots and settles into joints and textural depressions. There, it dries with a tenacious bond. It’s an easy way to restore the antiquing color to old or weather-beaten stamped concrete.
The final step involved sealing the restored surface. I like Euclid Chemical Co.’s EverClear VOX, a water-based acrylic sealer that's easy to apply, even in hot weather. As an added bonus, it can be sprayed from a cheap plastic garden sprayer as opposed to an expensive metal one. On stamped concrete, the satin sheen looks more realistic than a high gloss and is less slippery when wet. Although it doesn’t darken the color as much as solvent sealer, it does adequately enhance the slab’s appearance. In my own outdoor tests, it lasts longer than solvent acrylic sealers. The homeowners were ecstatic with the results.
An untapped market
I don't know why more contractors don’t realize the benefits of learning proper repair. Stamped concrete has been around for decades, so there’s a lot of it that could use attention.
You don’t need specialized tools, the materials are relatively cheap, it’s not physically demanding or time-sensitive, and it can be done by one or two people. Thus, overhead is extremely low.
Customers already have a mess on their hands, so they appreciate the contractor who comes in to save the day. I’m often called in by other contractors who are having problems. In all, repairing decorative concrete can be a very gratifying and lucrative specialty.
Steve VandeWater is the manager of The Concrete Store in Fishers, Ind. He’s a former Indianapolis-area contractor and creator of the Indiana Decorative Concrete Network website. E-mail firstname.lastname@example.org; for more information, visit www.indecorativeconcrete.com.