For the past decade solid countertops have led the way in kitchen remodeling but now a revolution is taking place in the kitchens of those who want a one-of-a-kind look, and that is the introduction of the concrete countertop. Not only is the look artistic but concrete countertops have the durability of the best solid counter tops only they are created with the homeowner in mind. In fact, like fingerprints and snowflakes, concrete countertops are rarely duplicated.
Concrete is not the easiest way to build and install a countertop. Just like ordinary concrete projects the countertop variety requires careful preparation and is subject to a curing process. In addition the design and must be carefully laid out before the pour and then finished so it will last the life of the home. In addition the labor and materials can be expensive and the kitchen can be tied up for as much as a week while the project is being completed
However, the final results are worth the time and expense. Not only will a concrete countertop be unique, and an instant conversation piece, it will provide many years of service. In fact concrete counters have been in use for centuries in different parts of the world.
1. Form the Form
The first step in a do-it-yourself concrete countertop is building a form. This is made from 3/4-in.-thick particleboard coated with melamine paint. This plastic paint covering helps the concrete dry slower so that it can cure for maximum strength. It also keeps the concrete edges smooth and prevents it from sticking to the wooden form when it comes to remove it. Drywall screws or a pneumatic stapler works for assembling the form that can be shaped or just made into a rectangle. To avoid splitting the composite board the wood should be drilled before putting in the screws. Sink holes, range top or deck-mounted faucets should be blocked out with plywood. These block outs should be the same height as the side boards so that the concrete can be made level with the top of the whole form.
2. Add Strength
As with building a solid, concrete sidewalk a strong countertop is fortified with diamond lath, reinforcing rods and polypropylene fibers. The diamond lath can be cut to fit with aviation snips to a length of one-inch short of the edges. In addition No. 3 (3/8-in.) rebar or reinforcing track should be placed around the sink cutout for extra strength to accommodate the weight of water.
3. Layer the Concrete
The concrete should be poured in layers with minimal time delays between pours so that one batch adheres evenly to the next. The longevity of a concrete countertop depends on how the concrete mixture is mixed. First, the dry ingredients are mixed thoroughly using a standard mason's hoe with holes. Then the liquid components - the latex additive, liquid pigment and water - is carefully measured and then added to the dry ingredients slowly.
For a good mix many installers use two quarts of white Portland cement for each 60-pound bag of concrete. Because of the great pressures on concrete as it cures it will want to crack. However, the polypropylene fibers, diamond lath and reinforcing rods fight the stresses to prevent cracking.
5. Two Mixes
For the best results two different mixes are required, one for strength and one for finishing. This is similar to sidewalk concrete preparation. The poly-fiber-reinforced concrete is for the core of the slab while a standard concrete finishing mix is used for the surfaces. A small amount of regular, finishing concrete is packed in about an inch thick around all of the edges. Then the reinforced concrete, diamond lath and reinforcing rods are added. Last, a full layer of finishing concrete is used for the surface.
The two different batches of concrete have to bond together so form a seamless block. This means the consistency and color have to be the same all the way through. That's why it is so important to measure ingredients, especially the liquids. The concrete should be just damp enough to hold together when you form it into a ball.
This is no time for soupy mixture because this thin consistency cannot not be compacted. This is why a dry, high-strength mixture is used in countertop projects. To achieve this the concrete mix is tamped down with a magnesium float so that it packs tightly into the form. Next the surface is smoothed with the float.
Small amounts of concrete are then added to fill low spots and cover pieces of aggregate. Larger pieces should be removed and the voids filled with fresh concrete. With a helper, strike or saw the surface with a piece of two-inch, square metal channel that should be at least eighteen-inches longer than the form. The bar is moved back and forth as the finishers move along the top of the form. The leading edge should be raised slightly so that it does not catch on pieces of aggregate in the mix.
The concrete is left to set for about two hours. Then the surface is smoothed with a steel trowel. If puddles of water occur on the surface the slab should be left to rest for 30 minutes and the process repeated. Take care to trowel the slab in three to four brief sessions. If the area is hot or dry cover the concrete with wet burlap or plastic to slow the curing process which will increase the hardness. The concrete should cure for at least 48 hours before the forms are removed. To put the countertop down get lot's of help! When in place put a bead of silicone around it to seal it and then seal the concrete with a coat of acrylic clear finish.
For more information on decorative concrete countertops our Contractor Directory for a contractor or simply post your project online.Posted by: kim