A Sunken Dining Room

Working near San Francisco at the Bay-area home of Jeanne Castro, host Ken Bastida uses the expertise of landscape designer Dan Berger of LandPlan in Pleasanton, California. Dan says that, not including plants, a homeowner would pay approximately $4,800 to have a professional complete the work. If you do the work yourself, the materials should cost about $1,000 without plants. On a scale of one to five, (with five being the most difficult), Dan rates the difficulty at four; the difficulty arises mostly from an estimated three weekends of hard work.

Preparing the Site

To maximize intimacy and privacy, choose a secluded corner near a fence or wall, or pick an open spot surrounded by trees or plants. Clear the site to bare ground, and use a can of landscaper's spray paint to mark the boundary of the pit for the table and seating. Make the pit five feet in diameter, with the circumference about six feet away from nearby trees, fences or other structures. Also use the paint to lay out the line of the curving stone wall at the front edge of your chosen site. Following the line of the wall, dig out a trench about one foot wide and two to three inches deep.

Building the Stone Wall

The wall is dry-stacked, using any type of sturdy native stone. Before beginning the wall, though, build the two sets of stone steps that will traverse the wall and lead to the seating area. Construct the steps and paths from two-inch-thick flagstone.

Next, backfill behind the boulder and end stones, and cover the top with a layer of tamped dirt. Place the first flagstone step on the layer of dirt, again checking for level and making sure the front edge slightly overhangs the foundation boulder. Over the rear of the first flagstone, build up a stack of narrow flagstones to serve as a riser for the next flagstone step. Backfill behind the riser stones until the dirt is level with the top stone (figure C). Lay the next flagstone step on the riser stones in the same manner as the first step. Repeat the entire process for the second set of steps.

Special Note

For this sample project, the ground level behind the stone wall is slightly higher than the front side, which means that the top flagstone step is at the same level as the seating area. If you perform your project on a completely flat piece of land, you will need to add steps behind the wall to bring you back to ground level.

Before building the stone wall, begin the drainage system for the bottom of the pit. Dig a straight ditch that starts about six inches from the center of the pit. The ditch should not pass through the center of the pit because the footing for the table column will be excavated there later. The discharge end of the ditch should be located well outside the project area where the drain pipe can empty freely. Because a drain flange and grating will be placed in the floor of the pit, the ditch needs to be at least two feet deep in the pit area. Also be certain that the floor of the ditch slopes down slightly as it moves away from the pit.

Continue building the stone wall, backfilling with dirt to stabilize the stones as you finish stacking each tier. Add stones until you reach an overall height of 18 to 20 inches.

Building the Seating Area

To make the liner for the seating pit, use 1/4" x 4" plastic header board. Header board will easily bend into the ring assemblies needed to form the cylindrical liner.

After making four more rings, stack all five together to build up the cylindrical liner. Be sure to fasten a few vertical braces around the outside of the liner to hold everything together (figure G). Next, excavate the pit to a uniform depth of 18 inches and center the liner assembly inside. Backfill the outside of the liner until the dirt is level with the lip.

The seating area is made of flagstone pieces that should be wide enough to serve as a walkway behind the seats. Evenly space about six of these large flagstones on the dirt around the pit, allowing them to overhang the liner. Carefully mark the inside curve of the pit liner on top of the overhanging flagstones (figure H). Use smaller pieces of flagstone to fill the gaps between the seats, shaping them with a hammer so that they fit together like pieces of a puzzle. Finally, where you previously marked the curve of the liner, score the flagstones with a hand grinder (figure I) and knock out the overhanging pieces with a hammer.

Building the Table

Before proceeding with the table construction, complete the work on the drain. Cut off the vertical extension of the drain pipe so that a drain flange and grating can be attached flush with the floor of the pit. Once the drain and grating are installed, keep them covered with a cloth while building the table column.

Excavate a hole for the column in the center of the pit floor. The hole should be about 16 inches in diameter and at least 18 inches deeper than the floor of the pit. Next, place a 10-inch-diameter concrete form in the hole. The form must be long enough to rest on the bottom of the hole and extend 10 to 11 inches above the surface of the flagstone seating. Fill the form with ready-mix concrete, trowel off the top to a smooth finish, and check the top surface for level. Wait at least 24 hours for the concrete to harden before removing the form. After the form is removed, use more concrete to fill the space between the column and the hole in the pit floor.

While the concrete sets up, begin making the tabletop by using a jigsaw to cut a piece of exterior-grade plywood 42 inches in diameter. Then use tile backer board that's cut to the same dimension as the plywood, and attach it securely to the plywood with coated deck screws.

Creating the Mosaic Design

Mosaic pieces for the table surface can be made from new or broken china dishes, or even from pieces of attractive stone. If dishes are used, first smooth off the feet with a hand grinder. Next, place one dish at a time upside down on a small piece of plywood and cover with a towel. Use a hammer to gently break the dish into smaller pieces. Carefully turn the plywood, towel and dish fragment assemblage over so that the basic pattern of the dish is preserved.

Finishing Up

After removing the cloth from the drain, fill the bottom of the pit with two to four inches of 3/4-inch decorative rock to enhance drainage and to keep the floor clean. Also fill the joints between the flagstones with decorative pebbles for a more finished look.

To mount the tabletop to the concrete column, center and attach a 20-inch diameter plywood disk to the top of the column with four concrete anchors (figure K). Center the tabletop on the plywood disk, and securely attach it from underneath the disk with coated deck screws (figure L).

Planting Plan

To accent the dining area, and to enhance the inviting, intimate appeal, Dan Berger suggests a number of flowering plants. A combination of flowering vines and lower, more compact plants are good to place next to adjacent fences or other structures. The effect of the stone wall can be softened with cascading plants.

• Lavender starflower (Grewia caffra), Zone 11, hardy to 45 degrees F is a favorite of Dan's, but you should check with a local nursery if you require a frost-tolerant variety.
• Society garlic (Tulbaghia violacea), Zones 7-10, hardy to zero degrees F, with its white, lily-like flowers is another attractive choice.
• Flowering maple (Abutilon pictum), Zones 8-10, hardy to 10 degrees F offers yet another possibility because of the colorful blossoms and leaves.
• Flower Carpet Pink rose, Zones 5-9, hardy to -20 degrees F, has vivid, deep-pink blossoms that will brighten any area from spring to autumn.