Concrete countertops come in a wide variety of forms: pre-manufactured slabs, cast-in-place, and custom precast. Concrete countertops, especially custom precast, offer nearly limitless design possibilities. They appeal to those looking for something unique, personalized and environmentally friendly.
The history of concrete countertops began about 25 years ago in the Bay Area of California. Artists used concrete as a medium for artistic expression to create highly sculptural, customized islands, countertops, vanities and fireplaces. The artistic, highly customized look has defined the public's idea of what concrete countertops are and is the main reason most people choose concrete: it's not like anything else and it can be endlessly customized to fit their unique tastes. Recently concrete's ability to be made environmentally friendly has also added to its appeal.
Concrete, when manufactured and fabricated correctly, can be a practical addition to any stone fabricator's repertoire. This article outlines the three types of concrete countertops and considerations for working with each type.
Pre-manufactured concrete slabs usually have exposed recycled glass as the defining visual characteristic. Slabs are generally similar in size and thickness to granite, and are intended to be fabricated alongside natural stone using the same machinery and fabrication techniques.
Pre-manufactured slabs fabricate and install just like granite. Some of the varieties available include a Terrazzo-like look with exposed recycled glass aggregate. Pre-polished slabs are also sized similar to natural stone, making them available as an "off-the-shelf" product.
Cast-in-place means the concrete countertops are cast and finished on site, directly on the cabinets. All the work is done in the client's home, from mixing the concrete to sealing the finished countertops. Cast-in-place is a risky option because of the challenges of doing all the work on site on top of finished cabinets, and the lack of job site control during and after casting. In addition the range of looks is limited, since most cast-in-place concrete is troweled. Grinding and polishing up against walls and cabinets is difficult and sometimes impossible to get into tight corners. Cast-in-place concrete countertops pros and cons include:
--Forming, casting and finishing on site on top of the cabinets can limit your options
-- Typically only a troweled finish is used
-- Seamless-some stunning effects are possible
-- The fabricator has little control over jobsite, and there's risk of damage to client's cabinets.
Custom precast concrete countertops are templated just like other countertop surfaces. The contractor takes the templates back to the shop and builds forms around them, then pours concrete into the forms. Once the concrete cures, the contractor processes and seals it to create the final look.
Custom precast concrete countertops can have integral sinks, drain boards, embedments and other features cast directly into the concrete. Additionally, custom precast concrete countertops can have any look, such as exposed aggregate, honed, troweled, acid stained and many more. Unlike pre-manufactured slabs, custom precast can be made in any thickness, with monolithic edges of 3 or more possible. In contrast, pre-manufactured slabs have to be laminated like natural stone, and the glue line is always visible.
With custom precast concrete countertops, each piece is custom formed and cast to fit the cabinets. Since each piece is custom shaped, no cutting is necessary, and since slabs can be made larger than pieces cut from a pre-manufactured sheet, fewer (and sometimes no) seams are possible.
Well-engineered precast concrete countertops can be strong as well as beautiful. Properly placed reinforcing, either steel or glass fiber, provides great strength without adding unnecessary weight and reduces or eliminates the risk of breakage.
Custom precast concrete countertops can be formed, cast, processed and sealed in a shop. Then they can be installed like granite. Pros and cons include
-- Nearly limitless look: polished, honed, exposed aggregate, solid, troweled, and nearly limitless custom colors, including mottling and patterns can be achieved; also, embedded materials, veining, integrally cast sinks, drainboards and complex patterned edges are all possible
-- Any thickness is possible with monolithic casting- no lamination lines, either
-- Each piece is cast to shape - no cutting, Therefore there's little or no waste
-- Concrete can use crushed scrap stone, recycled glass and more to make it very green.
Stone fabricators around the country are recognizing the demand for custom concrete countertops, and are considering adding concrete to their offerings. There are several factors to consider. Pre-manufactured slabs are easiest to add to a stone shop's offerings, because they are fabricated just like stone. Pre-manufactured slabs also have some "green" appeal because they incorporate large amounts of recycled glass. However, pre-manufactured slabs are not locally made. And, they don't offer the level of customization and personalization that consumers typically seek in concrete.
Cast-in-place is not likely a technique that stone fabricators would consider. Many decorative concrete contractors are able to use this technique with great results, since the finishing technique of troweling requires a great deal of skill and practice with concrete. This is not an easy skill to develop. Additionally, the risk of damaging a client's cabinets while working in their home with concrete is too great.
With custom precast, stone fabricators can choose to manufacture and install the concrete themselves, or, they could partner with an existing concrete countertop manufacturer. The benefit of partnering is that someone else handles the process of making the countertops. The downside is that the stone fabricator gives up control of the quality and the design, and a good portion of the profit, since someone else makes the countertop.
Whatever approach you choose, it is important to recognize that every cast-in-place and custom precast concrete creation is unique. There is no defined mix design, manufacturing technique or sealer that must be used. Sealers in particular vary widely, and the sealer dictates the final performance of the countertop in terms of stain-, heat- and scratch-resistance.
The Concrete Countertop Institute has published overall quality standards that are applicable to all three forms of concrete countertops. The standards allow for various levels of sealer protection. The Concrete Countertop Institute started a certification program in June 2010 that will help consumers find concrete countertop manufacturers who have proven that they meet the quality standards. Still, given the variations in performance, education of both the fabricator and the client is essential to ensuring quality, performance and customer satisfaction.
Jeff Girard, P.E., and president of The Concrete Countertop Institute, trowels a cast-in-place countertop in a kitchen.
A 40-foot cast-in-place bar top by Coastal Concrete Counters in Pensacola, FL.
Variegated concrete vanity with integral sink, intricate edging and custom color matched to the travertine backsplash. Inset: Intricate cast edges are possible in concrete countertops.
Decorative puzzle seaming is one benefit of custom precast countertops. This corner zigzag seam is a perfect example.
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