Granite Countertops

Solid-stone countertops are a pricey proposition due to the special tooling and installation required. However, their natural beauty, durability, resistance to heat and a sense of permanence add value to the kitchen as well as the home. You will need to prepare a solid sub-base of 3/4-in. plywood, then add a lightweight tile-backer material (called Denshield on Figure 2) over the plywood before laying out and installing the stone surface itself. In this guide we will install granite countertops. 

The trickiest part of installing stone tile countertops is cutting a crisp, clean countertop “nosing” (or front lip). This difficult task is simple when you use a homemade jig that’s clamped to a tile saw’s sliding table to cut perfect 45-degree miters.

To calculate the number of tiles you need, multiply the lineal footage of 24-in. wide countertops by 2.5. Then add as many tiles as required to cover wider peninsulas or islands and subtract for cooktops, stoves, sinks or other built-ins. Keep in mind that you’ll probably need partial tiles for filling around built-in appliances as well as at least a half dozen more tiles to allow for breakage and mis-cuts. Have extra tiles on hand; you can always return the leftovers.

In addition to the granite tiles, you will need :

  • 25-lb. bag of thinset mortar— gray for dark tiles or white for light tiles.
  •  5-lb. bag of unsanded grout for the tile joints. (Unsanded grout is easier to work into the narrow 1/8-in. wide grout lines and you won’t risk scratching the stone while grouting.)
  •  A quart of polished-granite sealer (about $25) to treat the tile and grout surfaces a week or so after grouting the tile. It will help prevent stains from penetrating the porous surface and enhance the natural beauty of the stone.
  •  One roll of fiberglass mesh tape for taping the Denshield seams.
  •  1/4-in. notched trowel for spreading the thinset.
  •  4-in. or 6-in. putty knife.
  •  2-in. margin trowel.
  •  A honing stone to soften sharp exposed edges.
  •  A grout float for spreading and embedding the grout.
  •  Color-matching caulk to substitute for grout at inside corners
  •  Plastic spacers for supporting the backsplash tiles.

Because you can’t score and snap it like ceramic tile, you should cut granite tiles on a diamond tile saw. In addition to standard carpentry tools, you can rent or buy the tile-cutting saw. Lay out all your tiles and plan ahead of time, have the underlayment installed and you can do all the cutting in one day. Use four rubber-padded mini-clamps to hold the tiles to the jig. Steel C-clamps may crack the tiles. But use a couple of small C-clamps to secure the jig to the saw table.

For the underlayment you will need the following materials :

  •  3/4-in. plywood underlayment: You’ll need a full sheet of 3/4-in. plywood for every 8 ft. of countertop.
  •  Tile backer: Buy a 32″ x 60″ sheet of Denshield (or cement board if Denshield is not available) for every five lineal ft. of counter.
  •  1×4 cabinet blocking: Pick up enough 1x4s and 2x4s to line the top of the cabinet backs, cabinet ends and areas where plywood splices will occur.
  •  1×3 backsplash trim cap: Buy enough 1×3 trim lumber that matches your cabinets along with the necessary stain and finish to cap off the finished backsplash.
  •  One 1-lb. box of 1-in. roofing nails for nailing down the Denshield.
  •  One 1-lb. box of 2-in. screws for securing the plywood to the cabinets and the 1×4 to the wall studs.

Preparing the Cabinets

The key to flat, long-lasting tile countertops is a solid plywood base. Thin cabinet sides or corner braces simply won’t provide enough anchorage to hold the plywood flat and stable. After the tops are removed, you’ll have to build up cabinet edges with 1×4 or 2×4 blocking along cabinet backs, ends and areas where plywood splices will fall.

Cut the 3/4-in. plywood underlayment to length so it splices over blocking using the factory edge of the plywood in the front for straight nosings. Cut plywood to length to fit flush with finished cabinet ends and 1 in. short of cabinets that butt against appliances like stoves or refrigerators.

Use Cement Board or gypsum-based material called “Denshield” with the core and the sheathing modified to repel moisture and accept a tile overlay with conventional bonding adhesives. It is lightweight and you cut, snap, rasp and fasten it exactly like standard drywall, and comes in 32 in. x 60 in. sheets, which is ideal for countertops.

Splice the Denshield where ever you wish, but keep in mind that all of the splices and the outside and inside corners need to be taped with fiberglass mesh tape and a thin layer of thinset, so avoid using lots of little pieces.

The miter jig (Figure 1) will fit on most tile saws, but it may need alteration for some models. Use any flat 1/2-in. plywood for the jig. A table saw is the tool to use. Cut the parts, then spread exterior-grade woodworker’s glue on the edges and tack them together with 1-in. nails. Rest the jig on a flat table and clamp a tile to the angled jig surface with the bottom of the tile resting on the tabletop. Then rest the narrow stop block against the top of the tile and glue and tack it to the jig.

Positioning and clamp the jig securely to get a perfectly even miter that ends right at the edge of the 1/16-in. factory cut micro-bevel on the tile edge. Cut some test tiles with the jig and make the fine adjustments until results are satisfactory. Use rejects for the rear row of tiles with the bad edge against the backsplash.


Laying Out the Tile

After the tile base is in place, spend some time dry-laying the tile to work out the best looking top. Inside corners are critical because the grout lines have to align in two different directions. ALWAYS start at inside corners and work your way towards the countertop ends. Spacers aren’t necessary, because you can easily eyeball the 1/8-in. grout lines for both dry-laying and the actual installation. 

On the countertop section containing the sink, work from both ends toward the sink.  That way, you can custom cut one or more shorter tiles near the center of the sink where they won’t be as noticeable.

Another advantage to laying out the tile ahead of time is that you’ll know if you have enough tiles. Mark the backs of tiles (write on masking tape) that need special cuts like narrower tiles at countertop ends or in the middle of the sink and tiles that need 45-degree angle cuts and the outside corner tiles. Cut miters on all countertop front and end tiles (outside corner tiles need miters on adjacent edges), then cut miters on opposite ends of half that quantity for the nosing. Cut the nosing tiles 2 in. wide. Use the leftover sections for the backsplash.

Other Edge Treatments

Wood edging: If you’re used to working with wood, this edge is by far the fastest and easiest of all methods. Before installing any tile, rip 1×3 wood that matches your cabinetry down to 2 in. wide, then rout the outside corner with any profile you wish. Leave off the Denshield nosing strip so you can glue and nail the nosing directly to the plywood. Sand and stain the wood then cut it to fit and fasten it to the plywood with construction adhesive and 3-in. finish nails driven into the plywood core. Use tiles and add another 1/16 in. to allow for the tile thinset to gauge how far the wood edge should project above the countertop surface so the wood and the finished tile top will be flush. Finish with three coats of polyurethane. Fill the grout line between the wood and the tile with matching caulk rather than grout or a crack will eventually develop between the wood and the tile.

Overlapping tile edges: As you can see, the front edge of the top tiles overhangs the nosing tiles, so the exposed, unfinished edge needs to be polished (we cut a simple 45-degree chamfer with the mitering jig, but you can leave it square too). This technique works best for marble or limestone tops because the material is soft enough to finish with an orbital sander and progressive grits of 100, 150 and 220 silicon-carbide or aluminum-oxide sandpaper. Begin by installing the countertop tiles first, overhanging the front edges using the same technique described above. Then polish the edges with a 4″ grinder fitted with a marble-polishing disk and install the narrow front pieces as we show in the main story.

Bullnosed edges: This is by far the trickiest method because it takes skill to freehand consistent edges with a right-angle grinder. Check around to find a stone fabricator who uses special machinery to bullnose individual tiles for a cost of about $12 per lin. ft. Lay out the tiles as shown in Photo 12, then mark the tiles that require edging. The downside of this method is that you won’t be able to finish your counters for several days while you’re waiting for the fabricator to finish. So it’s a good idea to lay out the tile on the old countertop and take the tile in for grinding before the demolition work starts.