Novice stampers are prone to making a few common mistakes. Some have to do with planning the job. Others have to do with misunderstanding the materials, while still others are simply a lack of familiarity with manipulating stamps and skins. Here’s an opportunity to learn the easy way.
Begin with the basics
Tim Frazier, head trainer at The Stamp Store in Oklahoma City, says stampers need a command of the fundamentals of slab design before they start stamping. “Is it going to be indoor or outdoor use? Will it be driven on or walked on?” he says, of important questions to ask before starting out. “Does it require a vapor barrier, and did you put the correct amount of sand on the vapor barrier so the water can evaporate in all directions? Do you have a quality mix, matching the psi and the thickness with what kind of work is being done on it?”
The fewer variables influencing your job, the better. For a predictable mix on slabs he’ll be stamping, Ron Heck of Ron Heck Construction in Indianapolis uses only limestone aggregate, not pea gravel or other rock. Because it’s uniform and doesn’t absorb water, the more expensive material is worth it.
Communicate with the customer
Watch out for overselling. No stamping job is perfect, and Steve Harriman of Harriman’s Bomanite in Spencer, Indiana, says he doesn’t push to sell the product. Instead, he lets customers make the decision. Going hand-in-hand with that, though, is encouraging customers to be well-informed.
"You have to have a good, frank discussion with them about what they’re going to get,” he says. “They’re not going to get a flawless piece of work. There might be some cracks. There might be some imperfections. And they need to know that upfront, so they’re not going to be surprised at the end when they see some things that aren’t perfect.”
Once customers have picked out colors and patterns, bring them 2-by-2-feet samples, and don’t bring just one, Harriman suggests. “Bring one that the customer thinks they want, one you’d like to see them do, and slight variations on what they want, maybe one darker and one lighter.”
If a customer wants something that’s a bad idea in your climate, don’t be afraid to say no, says Heck. In his area, which is prone to many freeze-thaw cycles, he won’t do overlays.
Don’t create slippery surfaces
When you’re designing the job, make sure you’re not creating slippery slopes, Harriman says. “We’re tearing out a slab that is too slick, and the people couldn’t walk on it,” he says. “The slopes were too strong, and when it got moisture on it, the people were falling.”
To avoid creating a slip hazard, a sloping path may need to be designed with steps or a new contour. But the surface needs enough slope for good drainage, so that algae and moss won’t thrive. Good drainage requires at least 3/16 inch per foot on a textured surface.
The choice of a pattern also affects traction. “You don’t want to have anything that doesn’t have much relief to begin with, because by the time you put the sealer on, it will be too slick,” Harriman says.
When it’s time to seal the concrete, a penetrating, water-based sealer creates a less-slippery surface than an acrylic coating does, Harriman says. But in the shade, that porous surface also harbors moss and algae, which can make the surface slippery. Harriman suggests adding a slip-resistant additive, such as H&C SharkGrip from Sherwin-Williams, to a coating.
Trying to pour a slab that’s too big to handle at one time is a common beginner’s error, says Heck. “I have a crew of four guys plus myself,” he says. “Yesterday we poured 6 1/2 yards of concrete, about 440 square feet. You want to max yourself out at no more than 7 yards at a time.” Heck says when a crew is stamping a very large slab, the stamping may start off looking good, but by the end it’s difficult to get an impression.
“Don’t pour more than you can handle and have plenty of help,” says Harriman. “Weather plays a huge part in how much you’re able to do. On a decent weather day, maybe 75 degrees, if you pour in the morning, if you have a complicated pattern, you might be able to do 400 to 500 square feet. If it’s going to be hot, you might have to reduce it to 300 to 400. That’s a hard lesson to learn.”