DEAR TIM: I need a recommendation for the finished surface of a small 42 inch long and 20 inch deep exterior potting bench and a somewhat larger outdoor kitchen top. I am on a limited budget and need a surface that is smooth and is more decorative than wood. My daughter would prefer pink if possible. The winters here can be bitterly cold so I want these tops to be maintenance free if possible. John C., Hartland, WI
DEAR JOHN: You can possibly get what you want and still be within budget with at least one of the tops. The potting bench top might be resting in the boneyard scrap pile of a local solid surface countertop fabricator. I have seen more than one pinkish-cast solid plastic countertop material that would be an ideal outdoor countertop surface. The craftspeople that make solid-surface countertops frequently end up with a variety of leftover scraps they sometimes sell for a song.
Depending upon how handy you are, you can get exactly what you and your daughter want, but the tops will be made from a material you may not have even considered: concrete. You can add permanent pink powdered pigments to Portland cement, get pinkish sand and even small pink stones for the aggregate to make the concrete. I'll wager that with a little experimentation, you will produce stunning pink countertops that will withstand countless Wisconsin winters.
Experimentation is necessary to determine the final color of the cured concrete, once it has dried for 30 to 60 days. The concrete will almost always look several shades lighter once dry than when it was first mixed. The degree of final smoothness of the finish will also affect the color. Smooth countertops are easier to maintain and believe me, it takes some practice to learn how to wield a steel trowel like a pro. Fortunately, the cost of the raw materials to make the concrete should be minimal and if your experiments produce just one cubic foot of mixture each time, you will waste very little money.
If you decide to use a natural stone material or ceramic tile, you need to make a base for these materials to rest upon. Indoor tops differ from outdoor tops because builders know they will stay dry. But your tops are sure to get wet and water will eventually seep under all of the countertop materials. This water and changes in humidity and temperatures can cause untreated wood to rot, swell, twist, expand and contract. This deterioration will lead to delamination of or cracks in the finished surface materials.
I would consider using treated plywood as the foundation for ceramic tile and natural stone tops. Chemically treated plywood will not rot if it comes into contact with liquid water. If you can't get treated plywood, buy special powdered chemicals that contain borates. Dissolve these into water as directed and saturate the regular plywood with the solution. Once dry, the wood will have superb resistance against rot and decay.
It sounds crazy, but I would cover the wood with 15 pound felt paper and let it drape over the edges. Fold the felt paper under the plywood 6 inches on each edge and secure it with staples. I would then screw one-half inch thick cement board to the treated plywood. The natural stone or ceramic tile will then be permanently bonded to the cement board with Portland cement-based thinset.
Keep in mind that the ceramic tile or natural stone products that are somewhat affordable are often found in uniform sizes such as 6 x 6 inches or even 12 inch squares. The spaces between the pieces are filled with sanded Portland cement grout that may or may not be epoxy-fortified. Regular sanded grout will work fine so long as you do not use too much water when you mix the grout and when you finish the joints. The water will dilute the cement in the grout and it will rapidly deteriorate.
Water is indeed the fiercest opponent that outdoor countertops face, especially in cold climates. The water can freeze and blast apart the countertop. The most common damage is delamination of the finished materials from the concrete base.
Pay attention to the directions on the thinset. Mix only as much thinset as can be used in 20 minutes. The cement board and finished countertop materials must be dust free. If you can slightly dampen them with water just before applying the thinset, you will greatly enhance the bond between the cement board and the finished materials. Once you spread the thinset onto the cement board, cover it with a piece of finished top material within three minutes if possible. If at all possible, erect a temporary shade shelter to avoid working in the sun.
