Planters enhance the appearance and the function of a deck, making
them popular add-ons for customers. Plantings soften the rigid look
of decking material and provide bursts of flower color that clients
love. Large planters filled with tall plants like ornamental
grasses or shrubs can be used to create privacy or conceal eyesores
like utility boxes and storage areas. And a planter that puts a
bounty of fresh herbs or tomatoes right at the chef’s
fingertips makes a perfect complement to an outdoor kitchen.
Of course, planter boxes are also a great upsell for deck builders.
But while they’re easy to build, they do require some thought
beyond simply constructing boxes and filling them with dirt. For
one, contained gardens can tack on a few hundred pounds —
especially once they’ve been watered — and the deck
must be able to handle the extra weight. It’s a good idea to
double the joists where the planters will sit.
Water presents other challenges — and opportunities as well.
Plants need it to grow and flourish, so you’ll have to
provide for drainage and shield the decking materials from
moisture. You can also increase customer satisfaction and your
profit by building in a watering system.
A liner keeps the wood of the planter box from directly contacting
soil moisture, which might cause rot or insect problems. For
clients who are planning on growing edibles, liners also prevent
any worry about lumber treatments leaching into the soil.
One option for a liner is a rubber membrane, such as PondGard from
Firestone (800/428-4442, firestonesp .com). Drop-in metal liners
made from copper or galvanized steel are another possibility, but
they can be tricky to locate and often need to be custom
We prefer plastic containers that we can drop into a wood frame.
They are quick, reliable, and — when you factor in the labor
costs of other methods — relatively cheap. The self-watering
EarthBoxes (888/917-3908, earthbox.com) used in this project cost
about $30 each (Figure 1).
Figure 1. A self-watering container like the one
shown above can be easily dropped into a wood frame.
Irrigation and Drainage
Container plantings tend to dry out quickly in the heat of the
summer and sometimes need a drink almost daily. No one wants to
drag a hose around all summer, though, so offer your clients a
Drip irrigation on a timer is a great way to simplify the chore of
watering and get plants the water they need. Irrigation tubing can
be run behind planters, or for a planter that sits out in the open,
it can be run underneath the decking and up through the bottom.
Then, individual tubes with emitters are placed at the base of the
plants to deliver water right where it’s needed. Numerous
sources, from home-and-garden centers to plumbing suppliers, sell
kits. Two to consider are Netafim (888/638-2346, netafim usa.com)
and DripWorks (800/522- 3747, dripworksusa.com).
An excellent alternative to drip irrigation is a self-watering
container. It comes with a reservoir, which needs only periodic
replenishments of water. When the reservoir is full, the water
slowly wicks through the soil, providing moisture to the plant
roots. To make watering even simpler for your clients, you can set
up an automated watering system to refill the reservoir.
While plants need water, they shouldn’t be swimming in it.
Good drainage is a must for planter boxes. Be sure the liner and
planter have adequate drainage holes. If you will be supplying the
potting soil, choose what is called a soilless mix, which typically
contains a blend of peat moss, composted pink bark, or coir;
vermiculite; and sand or perlite. Regular dirt from the backyard
tends to have poor drainage and can be the kiss of death for plants
in a container.
Building the Boxes
Because the dimensions of the planter assembly depended on the size
of the liner, we purchased the liners first and used them as a
guide. We also factored in the measurements of the decking
materials that we were going to use for the fascia.
Making the frame was straightforward; we fastened pressure-treated
2-by stock together with stainless steel screws (Figure 2). We
attached 3/4-inch pressure-treated plywood to the outside of the
frame — for stability as well as to provide a place to attach
the decking fascia (Figure 3). Then we screwed the planters to the
joists (Figure 4).
Figure 2. The outer frame of the planter box is
essentially a stud wall made from treated lumber.
Figure 3. A plywood face stiffens the
planter’s frame and provides nailing for finishes (left). The
author leaves out sections of plywood to fit the planters around
the newels (right).
Figure 4. Keeping the plywood above the decking
prevents it from wicking water, which could eventually cause
To support the weight of the soil-filled containers, we installed
2-by risers along the bottom of the planter boxes. These were
ripped so that the container’s lip would just barely rest on
the top of the frame (Figure 5). Next, a container was placed in
position, and a 21/2 inch hole for drainage was marked and drilled
Figure 5. Once filled with dirt, the liners will
be too heavy to hang from their rims. Risers ripped from 2-by stock
support the bottom of the liners. When installing the risers, place
them where they won’t interfere with the liners’
Figure 6. With the liner in place, the author
drops a marking pen through its overflow to mark the location of a
drain hole (left). The hole is large — 2 1/2 inches —
to prevent clogging (right).
The outside of the planter boxes is finished with TwinFinish
composite decking (TimberTech; 800/307-7780, timbertech.com).
Because it’s generally less affected by water than is wood,
composite decking is a great material for planters. To fasten the
lowest row of decking to the planters, we used screws from the
inside; we used hidden fasteners to attach the rest (Figure
Figure 7. The lowest piece of the
composite-decking facing is affixed to the planter from inside with
screws (left). Subsequent pieces are attached with hidden fasteners
The tops were a little more work than the sides. We wanted to cover
up the lips of the EarthBoxes, yet allow them to be removed. So we
ripped the decking to the right width and rabbeted the edges to fit
over the EarthBoxes (Figure 8). To allow for removing the boxes,
the tops are fastened down with screws, whose color matches the
decking (Figure 9). A small piece of decking material finishes the
corners (Figure 10).
Figure 8. The top of the planter is made from
composite decking rabbeted to overlap the liner rims.
Figure 9. Screws hold down the surface facing,
allowing it to be removed should the homeowners want to pull out
Figure 10. Trim pieces are nailed home.
After we built the planter, we installed a cable railing system to
allow maximum light to reach the plants while still providing
safety. Check with your local inspector about railing heights. Some
inspectors measure from the decking, some measure from the top of
permanent structures such as planters and benches.
Brent Benner is a carpenter, and
Jennifer Benner, his wife, is a horticulturist and
writer. They live in Roxbury, Conn.