July 2015 Job of the Month:
Decorative concrete isn't limited to horizontal surfaces like floors, countertops and patio decks. We can also use concrete overlays to cover up vertical surfaces. It isn't easy, since we have to fight against gravity, but this is a challenge we face regularly. Every time we lay down an overlay on a patio, we also cover up the vertical sides of the existing concrete. A larger project, like the concrete fireplace hearth at this office, can be trickier, but we can do it.
The fireplace was at the sales office for a property-development business. Their clients would visit the office and see the fireplace which had interior walls made of gray firebrick and a front facade made of yellow stone. The owners were not in love with the yellow and contacted us about covering it up with a more neutral color. They wanted a new color to complement both the floor of the waiting room and the wooden wall around the fireplace. We got to work on a cast-in-place concrete fireplace hearth by building a cement board frame and base around the yellow stone. We screwed together two layers of cement board for added strength. Next, we laid down the overlay on top of the cement board.
Vertical jobs like this one take longer than horizontal projects. For these applications we have to modify our overlay materials to make it work correctly for vertical surfaces. These special overlay formulas are designed to go on thick without sagging, which makes it possible to apply stamps and other effects to vertical concrete overlays. We wouldn't be applying a stamp this time, though; the business owners wanted a smooth surface for their new concrete fireplace hearth. Part of the process involves not applying the overlay material all at once, instead, we put it on in 3-4 thinner coats. This method helps prevent sagging. We used tools such as rollers, rakes and trowels to spread the overlay mixture evenly across the concrete fireplace hearth. This created a smooth, level surface across the entire overlay.
The overlay mixture we used for the concrete fireplace hearth had pigment mixed into it that created a gray color but it was not quite the shade we wanted, we needed something closer to that of the wall and the concrete floor. We used a water-based dye stain to bring the color in a little closer. In most projects, we'd have the option of using either a water-based dye stain or an acid stain, but as there is no such thing as a gray acid stain we had to go with a dye stain.
We wrapped it up by sealing the surface of the new concrete fireplace hearth. We made no changes to the firebrick inside the fireplace. We also didn't touch the shelf outside the fireplace per the request of our client. It was an unusual arrangement as we would have usually extended the overlay to the sitting area. However, the business owners were satisfied with it. The finished concrete fireplace hearth was an attractive gray with some variegation effects from all the troweling we did. It came out looking great.