Today's owners are looking for upfront economics, security, flexibility, and long-term durability. Completing the wish list is the owner's interest in a building that will represent the quality that they offer and become a statement in their area. There is no doubt that site cast tilt-up concrete answers an owner's requirements. The architectural advantages are proving to be the primary reasons for it becoming not only a viable option for other building types, but also a leading design medium for creativity due to recent innovations in architectural finishes. Part of the reason for the growing success of tilt-up is the advancements that product suppliers have made in recent years.
Contractors are now engaging a variety of technologies and processes to add greater variety to the palate available to architects and designers. From architectural features such as cornice lines and accent bands to the façade enhancements of thin brick, block, and stone, as well as a multitude of textured coatings, architects now have limitless possibilities for creating an aesthetically appealing structure.
One decorative architectural finish that has been popular with tilt-up concrete contractors for several years incorporates kiln-fired, ¼-inch thick bricks milled to tight tolerances with the exterior surface of the tilt-up panel. The bricks are placed on the floor slab within the panel forms to build a brick wall horizontally on the casting bed. A variety of methods secures these bricks during concrete placement and creates the “tooled” mortar joint look once the panel has been lifted into place. The brick faces are coated with a thin wax to prevent discoloration by the cement paste. The coating is power washed off after erection. Further, the brick has no impact on the structural performance of the wall, and it can be installed in almost any climate or weather condition.
Since the mortar joint is composed of the concrete placed for the panel, it can be enhanced with color additives. This is a definite advantage when trying to match adjacent projects using a combination of the thin brick and color in thin fascia applications of tilt-up sandwich panels. As with standard brick, thin brick systems can be placed in a running or stacked bond configuration with soldier and header courses. The bricks are available in a full spectrum of colors and textures with additional shapes for corners and returns.
Tilt-up is not limited to incorporating brick to achieve a masonry scale. Architectural concrete masonry units are placed in the forms horizontally—similar to the thin brick systems—providing another architectural option for tilt-up and adding a growing market for block manufacturers. Embedded masonry provides the aesthetic versatility and scale some designers find in masonry, while capitalizing on the speed and economy of tilt-up construction. Masons, mortar, and the traditional masonry schedule are removed from the project and minimal handwork is required. Unlike conventional masonry construction, the block units are free of the constraints of gravity, since they are embedded in the placed concrete of a tilt-up wall panel. This makes unique design patterns possible, including mosaic or tile patterns without complicating the construction schedule.
The key unit of the system is the “facer,” an architectural concrete masonry unit approximately 2 inches thick that has been specifically engineered for the application. The facer is laid on the forming surface in the desired pattern. Crews clip together adjacent units to stabilize them and seal the joints with sand to inhibit bleed-through of cement paste. Once this is completed, the tilt-up construction process proceeds as usual.
Painting is the most common method of finishing a tilt-up panel. While this technique has been available for decades, new advances in textured coatings have increased the variety and flexibility of this finishing method. Textured coatings can provide finishes from varying grades of surface texture to surfaces as visually stimulating as simulated stone—giving a new look to the traditional painted concrete wall. Further, many coatings have been fully tested and shown to last up to 25 years, which is four to five times longer than conventional paint.
A key difference between paint and coatings is the thickness of the application placed on the wall. Coatings are installed at the 15 to 17 dry mils range, while painting is typically 1/3 to 1/6 of that thickness. The thicker textured coatings will camouflage the minor cracks and imperfections that are commonly found on the surface of concrete panels. The coatings can be applied to damp, dry, cured, or uncured concrete and in a broad range of temperatures as low as -35° F.
Technology will continue to bring new finishing ideas to tilt-up for years to come. More simulated, faux, or “thin” materials will continue to be introduced, as well as improvements in coating materials. As the diversity of finishes expands, tilt-up will be used more frequently and further penetrate markets throughout the globe.
— Ed Sauter is executive director of the Tilt-Up Concrete Association. He can be reached at 319-895-6911 or email@example.com.