Concrete woes blamed on poor guidance
Q: I have a big problem. Concrete was poured around my new swimming pool. I wanted a colored, sanded finish that resembled cobblestones.
Four weeks later, the concrete has a milky, splotchy appearance and the finish is rough on bare feet.
What, if anything, can be done to salvage this job? How could the mistake have been prevented? — Tom H., San Jose, California
A: Oh, my! The photos you sent me tell the tale. Believe it or not, from what I can see, the concrete finishers did a remarkable job. They used the correct sand in the mix to produce a nice, sandy texture, and they washed just enough cement paste out to produce a gorgeous exposed aggregate finish.
I realize, though, that this is not what you had envisioned for the final product. Can you see the problem? What you picture in your mind and what another person envisions based on your verbal description can be miles apart.
You may have wanted a stamped concrete look that resembles actual cobblestones. For all you know, the contractor might not have ever seen a cobblestone alley, street or sidewalk.
To achieve a stamped cobblestone look, concrete finishers broadcast dry pigments into the wet concrete, mix these into the top layer of the concrete and then lay rubber mats onto the concrete that have the cobblestone texture and outline.
These mats are tamped into the wet concrete and then peeled off. The concrete then looks just like cobblestone.
Based on your email to me, I don’t know that this is exactly what you wanted. It’s a classic case of miscommunication. You could have prevented this situation by giving the contractor a few excellent photographs of what you wanted.
If the concrete finish you wanted can be found at a local business, park or other place, you could have taken the contractor there to show him.
Countless YouTube videos show patterned and textured concrete.
If you want actual stamped concrete, you have to start over. You need to tear out all the concrete and replace it.
If you just want a different-colored finish that's less rough, you might be able to produce it with a very thin cement stucco overlay that's no more than inch thick.
Your big challenge is that you can’t add much thickness where the concrete slab touches up against the cast border of the swimming pool. You need positive drainage away from the pool.
You can create a unique cobblestone finish using the thin overlay, stencil templates and some dry pigments.
You can also create the look of flagstone, tile or even brick. Shaded coloration is very possible — so it's not just one uniform color when complete.
An expert concrete mason can make up the thin overlay cement stucco and colorize it. He would apply this over the new concrete, smooth it and then overlay heavy paper templates that might resemble brick or the cobblestone outline.
These are lightly pressed into the wet stucco, with an additional dry pigment then broadcast onto the stucco.
The paper template prevents the second color from touching all the stucco. The concrete mason floats the pigment into the stucco and then might use a few special rollers to create a unique texture to the overlay.
The contractor shouldn’t be penalized for this mistake. The photos suggest that he did a great job and that you didn’t get the final finish you wanted because of poor communication.
Before you tear up the existing concrete, do a small test to see whether the stenciled overlay will produce the finish, texture and coloration you want. I think it's possible to get very close, and the work could be done in just one or two days.