Tiered Concrete Planter

Hi everyone!

We are Well Structured, a group of young women from the Girls in Engineering Academy (GEA), a program run by the Engineering Society of Detroit (ESD)! For our class project, we worked together to design and build the "Tiered Concrete Planter", a four-tiered concrete planter system held together by interconnected PVC pipe supports.

We wanted to jump into the worlds of structural engineering and environmental design hands-first! Along the way, our team did it all. We sketched diagrams, built cardboard prototypes, figured out concrete mixing ratios, and cast custom molds with built-in PVC connectors. To wrap up our creation and give back to nature, we hand-picked and planted local native flowers, host herbs, and nectar plants to create a cozy home for butterflies, hummingbirds, and other pollinators.

We hope you enjoy building it as much as we did!

Tools and Safety Gear:

1. N-95 Facial Mask
2. Mechanic Gloves
3. Safety Glasses
4. Trowel
5. Hot Glue Gun & Glue Sticks
6. Scissors / Utility Knife
7. Permanent Marker
8. Tape Measure
9. Hammer
10. Sand Paper
11. Miter Saw

Materials:

1. 2 - 50lbs Fast-Setting Quikrete Concrete Mix Bags
2. Cardboard Boxes
3. Heavy-Duty Packaging Tape
4. 6ft - 1 Inch PVC Pipe
5. 16 - 1 Inch PVC Pipe Caps
6. Plastic Solo Cup
7. 5-Gallon Bucket
8. Small Rocks
9. Potting Soil

Plants (Pollinator Friendly):

1. Native Flowers
2. Purple Coneflower
3. Cranesbill Wild Geranium
4. Butterfly Weed
5. Wolf Violet
6. Yellow Woodsorrel
7. Native Host Herbs
8. Dill
9. Rue
10. Fennel
11. Non-Native Nectar Plants
12. Lantana
13. Coreopsis
14. Egyptian Star Cluster
15. Ageratum

Before mixing any concrete, our team sketched a scale side-view diagram to plan out the geometry and weight distribution. From there, we mapped out the dimensions of each individual planter. The great thing about this project is that it's fully customizable! You do not need to follow our dimensions, but these are what we found worked best for us!

1) Plan the Tiers

Design 4 distinct planter levels arranged at varying heights to form an interconnected structure. Find where each support will go into each planter for best weight distribution. For example, our Pot 1 and Pot 2 will serve as the main ground-level foundation base, and Pot 3 and Pot 4 form the elevated upper tiers supported by vertical PVC legs.

2) Build a Test Model

Construct a prototype using cardboard boxes and plastic tubes to test the stability and visual arrangement.

3) Map the Dimensions of Planters

Measure and mark out the specific length, width, and height for each of your 4 planters. Then, mark out the inner cavity where the plants will sit. Finally, mark out where the connectors will sit.

For ours:

1. Outer Dimension

Length - 15 inches, Width - 9 inches, Height - 3 1/2 inches

1. Inner Cavity

Length - 9 inches, Width - 6 inches, Depth - 2 1/2 inches

It will sit in the center of the outer shell, leaving 3 inches from the width walls and 2 inches from the length walls.

1. Connectors

The connectors have a 1-inch diameter. They will sit 1/2 inch from the walls in the corner.

Cardboard makes a fantastic, low-cost mold because dry concrete doesn't stick to it! However, cardboard does absorb moisture from fresh concrete mix. To combat that, we used heavy-duty packing tape and taped off the cardboard areas holding the mix. This let all the moisture remain in the mix!

1) Select and Prepare Outer Cardboard Molds

1. Select four clean rectangular boxes that fit your dimensions.
2. Use scissors or a utility knife to cut away all flaps and tabs, making sure the cuts are smooth and even.
3. Apply heavy-duty packaging tape directly over the entirety of the box interior, making sure all corners, slits, and seams are covered to prevent wet concrete leaks.
4. To keep the cardboard from bowing outward under the heavy mix, wrap packaging tape around the outside perimeter of each box three full times.

2) Create and Attach Inner Cardboard Pot Cavities

1. Select smaller cardboard boxes or create small boxes with leftover cardboard that fit your dimensions.
2. Wrap the exterior sides and bottom of each smaller box completely in packaging tape.
3. Center the smaller box upside-down inside the larger cardboard mold, leaving equal space around all edges for the concrete outer walls.
4. Attach the inner box using hot glue. You may also tape over the glue to ensure there is no concrete leaking under.

3) Place and Attach PVC Connectors

1. Use a permanent marker to outline connector locations on the bottom inside face of each mold, keeping them an equal distance (in our case, 1/2 inch) away from the outer walls and corners.
2. Hot-glue the PVC connectors facing downward inside the molds according to your design.

For our design:

1. Pot 1: Glue 2 connectors along one short side.
2. Pot 2: Glue 4 connectors, one in each corner.
3. Pot 3: Glue 2 connectors along one short side.

NOTE: Pots 3 and 4 also have connectors at the bottom of their pots, which we will address during the pouring step.

Pro Tip!

If you want built-in drainage holes at the bottom of your concrete pots, insert them now! Hot-glue small plastic straws vertically to the bottom of the inner box cavity and wrap them in packaging tape. When you strip away the cardboard and tape during demolding, the straws easily pull out, leaving clean drainage holes!

Safety First!

Put on your N-95 face mask, mechanic gloves, and safety glasses before opening and mixing dry concrete!

1) Measure Your Ratio

1. Use a plastic Solo Cup to maintain a 1:4 water-to-concrete ratio.

For example, each of our planters required 5 cups of water for every 20 cups of dry Quikrete mix!

2) Mix (for one mold)

1. Pour necessary water into the 5-gallon bucket before dry mix. This helps reduce airborne dust when combining!
2. Pour the corresponding ratio of dry concrete mix into the 5-gallon bucket.
3. Stir thoroughly with a trowel until fully blended. It should resemble an oatmeal-like texture.

Time to pour!

1) Pour

1. Carefully pour the wet concrete into the space between the outer and inner cardboard molds.

2) Settle Air Bubbles

1. Tap the outer sides of the cardboard boxes lightly to eliminate trapped air pockets, then smooth the top surface with your trowel.
2. Let them cure completely for 24 hours.

3) Repeat Steps 3 and 4 for Pot 2

3) Special Instructions for Pots 3 and 4!

1. Follow steps 3 and 4 as listed.
2. Both Pots 3 and 4 require four connectors embedded on the bottom.
3. Press the connectors gently into the wet concrete until they sit flush with the surface, making sure you align them with your planned measurements (for us, 1/2 inch from walls and corners). This is important to make sure the PVC supports are straight!
4. Since PVC is buoyant in concrete, place small rocks into the connectors to keep them in place.

To connect all four concrete planters into a sturdy, multi-level tower, you'll need to cut custom vertical support legs out of your PVC pipe!

Using a miter saw, we took a 6-foot PVC pipe and cut it down into eight specific support pieces.

1. Two 12-inch Pipes

These are used for the longest vertical supports to connect Pot 2 directly up to Pot 4. (Represented in the blue circle.)

1. Four 6-inch Pipes

These are used for middle-tier supports linking Pot 1 and 2 to Pot 3. (Represented in the yellow circles.)

1. Two 3-inch Pipes

These are used for the middle-to-top tier supports between Pot 3 and Pot 4. (Represented in the red circle.)

Tip: Make sure your cuts are as straight as possible! Due to slight variability in the spacing between embedded connectors in Pot 3, be open to trimming the smallest pipe down to achieve proper height and even support for Pot 4!

Almost done!

1) Demold

1. Once cured, peel away all the inner and outer cardboard and packing tape.

2) Clean Up and Sand

1. If there were leaks into the inner cavity, use a hammer to knock the dried pieces out.
2. Use sandpaper to sand down any rough edges.

Remember! These planters won't come out in a perfect rectangle. That's what gives them character!

Time for assembly!

1) Base Tier

1. Pots 1 and 2 will be the base foundation. Lay Pot 2 down on the left and Pot 1 down on the right.
2. Place the longest (12-inch) PVC supports into the furthest left connectors in Pot 2.
3. Place the four 6-inch PVC supports in the remaining connectors in Pots 1 and 2.

2) Middle Tier

1. Align the embedded connectors on the bottom of Pot 3 with the 6-inch supports extending upward from Pot 1 and Pot 2.
2. Press Pot 3 firmly into place, ensuring all PVC supports seat securely inside the connectors.
3. Place the shortest (3-inch) PVC supports into the top connectors in Pot 3, checking to ensure they sit level with the long supports coming from Pot 2.

Note: Cut or trim the small PVC supports now if necessary to achieve a level fit!

3) Top Tier

1. Align the connectors on the bottom of Pot 4 to the remaining supports extending from Pot 3 and Pot 2.
2. Press Pot 4 firmly into place, making sure all PVC supports are fully secured into the connectors.

4) Optional: Aesthetics

1. Sand and paint the exposed PVC pipes to match your desired color palette or planter finish!

We disassembled our planter to pot it, but it is completely okay to keep it together!

1) Fill Each Planter with Soil

1. Add rich potting soil to each cavity

2) Add Plants

1. Plant your choice of plants to fit appropriately in each level.
2. Water gently.

Move your completed Tiered Concrete Planter to a bright, sunny outdoor spot where local pollinators can easily find it. Give your plants a generous initial watering, sit back, and watch the butterflies, hummingbirds, and other pollinators visit your new garden structure!

Thank you so much for following along with our project! As young women in STEM, our team had an incredible time brainstorming, prototyping, mixing, and assembling this multi-tiered planter!

We truly appreciate you taking the time to check out our build! We hope you enjoyed creating your own Tiered Concrete Planter as much as we enjoyed designing it!

Happy building!