Making A Seat Wall Planter

Figure A

Homeowners Shirley and Paul Flaskerud live in the wine country of California. Their front yard is adjacent to their neighbor's backyard and fence. They want to add screening to make the yard more private and incorporate more seating. Their yard is 37 feet long and 19 feet wide, boxed in by a house on one side and fences on two other sides (figure A).

Landscape designer Nancy Driscoll designs stone walls and planters with a wine-country feel. She says that stone planters have a timeless quality and add architectural integrity to a space. Her design includes a cap on the stone walls to add seating in the garden. A seat wall should be built to a comfortable 18 inches high — the standard height for seats. Although her design includes two parallel stone walls, this project focuses on the one wall planter.

Driscoll figures that a professional would charge $2,100 for two stone walls (not including plants and sod), but do-it-yourselfers could build them for $700 in materials. This project is a 3 on a scale of 1 (easy) to 5 (hard) because of the stonework and can be completed in two weekends.

Step One: Marking the Layout

To determine where the seat wall will go, use any fixed object as your starting point. In this project, the existing concrete patio is the baseline, and the wall will be 14 feet long. After choosing and measuring your area, hammer in stakes at each end and run a string line between them.

Figure B

Drive in a few more stakes to mark the perimeter of the planter, which is four feet long and three feet deep, in the middle of the wall. Mark the outline using landscapers spray paint. The wall will be 10 inches wide where it borders the planter and 14 inches wide on each end. Prepare for the footing by digging out trenches about 12 inches deep (figure B).

Figure C

Step Two: Pouring the Footing

Place 1/2-inch rebar stubs, 32 inches long, every 16 inches along the footing, hammering them nine inches into the ground to provide vertical reinforcement for the wall and planter. Link the rebar stubs together with horizontal pieces of rebar, connected with tie wire (figure C).

Figure D

Tie another string line between the vertical rebar to set the height of the stone wall — 16 inches high to leave room for a 2-inch-thick cap. Fill the trench halfway with concrete and smooth out the surface with a trowel. Allow the footing to set up overnight (figure D).

Step Three: Building the Rock Wall

Driscoll selected muted gray and tan Mule Creek wall rock, which has fractured surfaces and is easy to build with. The rocks cost $500 for this project. However, there are a lot of options for price and aesthetics.

Figure E

The first course of rocks is below grade, completing the wall's footing. Apply a generous amount of a standard mortar mix on top of the concrete, and set the rocks on top of it (figure E). Work in small sections and line both sides of the footing. Then go back and fill in the middle with more rocks.

After completing the first course, continue building more layers on top. Vary the size, color and texture of the rocks to achieve a rough-hewn look. Set the flattest side outward to maintain the straight line of the wall. Break stones as needed to create the shapes you need.

Figure F

Set a metal channel (figure F) at each end of the planter's inner wall. These were custom-made by a welder for $45 each. They will help finish off the fourth wall of the planter later.

Figure G

Build up the wall to the string line, embedding the rebar frame as you go. Then go back and scrap out the excess mortar along the face of the wall. This technique, called "blind mortaring," gives the wall a more natural, dry-stacked appearance (figure G). After you complete the wall, allow the mortar to set overnight.

Step Four: Capping the Wall

Driscoll chose a two-inch-thick Connecticut blue flagstone for the cap ($240 per ton). With a hand grinder, cut the large slabs down to pieces that are about 36 inches long and 16 inches wide. This allows for one inch of overhang on each side. Lay out the flagstone on the wall to determine what shapes or angles need to be cut so that they will fit together like puzzle pieces. Grind down any sharp edges on the stones and rinse them off to remove dirt and grime.

Lay out the flagstones on the wall, leaving 1/2-inch joints between them. Tie a string line along the front wall so that you maintain a straight edge as you mortar the pieces in place.

Figure H

Remove each stone one by one and apply a 3/4-inch-thick bed of latex-based, thin-set mortar ($15/bag at home supply stores) to the top of the wall. Apply a bead of adhesive to the underside of the stone (figure H) and then set it in position on the wall. Tap the stone with a rubber mallet to ensure that it is firmly set and level. Continue mortaring the cap stones in place along the wall, being careful to line up the edges.

Figure I

Once all the cap stones are in place, use a masonry bag to apply grout into all the joints. Wipe off any excess (figure I), and allow the grout to set up overnight.

Figure J

For the back wall of the planter, use pressure-treated 2x12 planks instead of rocks because they won't take up as much space. Cut the boards to length and slide them into the metal channels installed earlier (figure J).

Planting: For More Privacy

To create more privacy and a sense of spaciousness, Driscoll chose plants with a fine texture. She plants a crape myrtle that has lavender blooms in summer in the stone planter. She also lays a sod lawn to make the garden cool and lush. Rounded trees in the back beds help disguise the back fence, and flowering shrubs and bushes soften the lines of the house. Her planting plan includes:

American arborvitae (Thuja occidentalis), Zones 2-7, makes a great privacy screen because of its full form
Hens and chicks (Echeveria imbricata), Zones 9-11, succulents with fleshy gray-green rosettes and orange flowers

The rough-hewn stones add a timeless touch to the garden, and the flagstone cap lends a finished look with extra seating space for a gathering of friends. The central planter is the ideal space for a crape myrtle — or any small tree — to provide a focal point and more privacy. The side beds, filled with an assortment of plants, make the space feel larger and softer.