How to Build a Greenhouse Potting Bench or Table

I need to start off by apologizing. When I first released our Beginner’s Guide to Using a Hobby Greenhouse, I enthusiastically promised that a tutorial on how to build a greenhouse potting bench was “on the way soon!” Welp… that was over a year ago now. My bad! So, I’m very sorry it has taken me this long to write this up for you.

See, I was waiting because we had planned to build a new potting bench and document the step-by-step process for this tutorial. We haven’t done that yet, so I put off sharing. However, a college buddy of mine recently reached out to ask how we built our greenhouse benches (after he saw my unfulfilled promise on the greenhouse article… lol). I admitted I was slacking, but sent him some tips along with many photos of our completed redwood benches to use as a guide. Not only did he nail the design, but he took a bunch of progress pics for us to share here. Thank you Luke!

Follow along to learn how to build a greenhouse potting bench, or several! We’ll go over a list of supplies needed, size considerations and suggestions, our design and alternative variations, and instructions on how to put it all together. For all you visual learners, I’ve included ample photos to go along with this simple design.

Disclosure: This post may contain affiliate links to products for your convenience, such as to items on Amazon. Homestead and Chill gains a small commission from purchases made through those links, at no additional cost to you!

DIY Greenhouse Bench Design: General Notes and Alternatives

What type of wood should I used to build a greenhouse potting bench?

Our greenhouse potting benches or tables are constructed with redwood lumber (a combination of heart and common), which has excellent natural rot-resistance. Cedar is another great choice. In general, hardwoods like redwood and cedar have superior durability, termite-resistance, and an increased lifespan than softer woods like pine. Since your greenhouse benches likely won’t be in direct contact with food and soil, you could use treated lumber if you desire (unlike constructing a raised garden bed, where I advise against that).

Should I seal the wood?

As you can see in the photos, the tops of the benches are slotted with space between the wood planks to allow water to freely drain. Even so, our benches don’t get super wet very often. We keep the majority of our greenhouse seedlings and plants nestled inside 10×20 trays or with other saucers below, so there isn’t water running onto the benches on a regular basis. Because of this we chose not to seal the redwood and simply left it raw, as-is from the store.  

If you happen to live in a very humid environment, or if you plan to water in a manner that is always draining onto the benches, you may want to apply a sealer or wood oil to help protect them. Or, if you’re concerned about maintaining their appearance. When our greenhouse benches get wet (especially with dirty water) it does leave water marks or light stains on the wood. But we don’t mind, and the marks could also easily be sanded away.  

Other options

As an alternative design, you could also build a greenhouse potting bench with a wire top instead. Use our design to create a similar frame/base, and then secure sturdy galvanized (rust-proof) wire on top of the bench instead of wood slats.  Be sure to include the horizontal top supports so the wire won’t sag though! This general design can also be used to create benches or tables for other applications. For instance, we used a very similar process to build our DIY potting bench – just a bit taller, deeper, and with a solid wood top. (Photos of our potting bench are included below)

Greenhouse Bench Sizes

Our greenhouse is 6 feet wide and 8 feet long. So, we built two benches that are 68 inches long (just shy of 6 feet), 22 inches wide, and 28 inches tall to fit along the side walls, and one bench that is a tad wider but shorter to fit along the back wall (66″ long and 24″ wide). See the photo below.

Use this general design to build a greenhouse potting bench of any size. Measure your space, and do whatever best fits your greenhouse! Here are some considerations when choosing dimensions:

Length

We designed our benches to maximize every inch of usable space inside. Together, the three benches (just under 6 feet long each) create a U-shape that lines the three sides of our greenhouse, with just enough space to work between them and the entryway. My buddy Luke followed a similar layout as ours, but on a larger scale. In his 8×12′ greenhouse, he built a bench that is just under 8 feet for the back wall, and one just under 9 feet for the side. Do keep in mind that the longer they are, the heavier and more awkward they’ll be to move or rearrange.

Width

We opted for 22-inch wide (deep) benches for a couple of reasons. One, that is what fit best in our fairly small greenhouse while still providing room to move around. Also, we considered the size of average seedling supplies since that is what we primarily use our greenhouse for – raising veggie, flower, and herb seedlings for the garden. Most seedling heat mats are just under 2 feet wide, designed to fit common 10×20 trays used for holding containers of seedlings. (10×20 trays get their name from their dimensions). Finally, about 2 feet is a comfortable width to reach across. Yet if our greenhouse were wider than 6 feet, we may have made the benches a tad wider like Luke’s too.

Height

Our greenhouse benches are about 28 inches tall (28.5″ once the final top boards are installed). Standard table height is 28 to 30 inches. This height works perfectly for raising seedlings and is comfortably ergonomic to work around. Luke is a tall dude and also has a taller greenhouse, so he constructed his potting benches at 34 inches tall.

Take into account the types of plants you intend to grow, and the overall height of your greenhouse. I have also seen much shorter greenhouse benches, which will provide more headroom above for tall plants – such as potted tomato plants, cannabis plants, or similar lanky friends. Of course, large potted plants could also be set right on the floor of the greenhouse.

Additionally, our greenhouse is located in a tight spot between our house and a fence. Keeping the plants up off the floor provides them the most natural light and less shade. We also built and installed our greenhouse on top of a 12” tall homemade concrete block foundation, which gave us an additional foot of headroom inside.  

Supplies Needed to Build a Greenhouse Potting Bench

• Four 4×4’s for legs, cut at the desired bench height. You could also use 2×4’s, but we prefer the added stability that 4×4’s provide.
• 2×4’s boards. You’ll need two equal-length boards for the long sides of your bench, and two shorter equal length boards to create the top rectangular frame, plus extra pieces for leg and frame supports. Again, ours varied between 66 or 68″ long, and 22 to 24″ wide.
• Thinner finishing boards for the top. We used 2.5″ x 0.5″ redwood planks similar to these ones (but not exactly) and found them in the interior finishing lumber section of our local Home Depot. Each bench required 7 planks, spaced about 1 inch apart. Luke used 8 planks since his benches are a couple inches wider than ours.
• 2.5 or 3-inch long deck screws or wood screws for frame assembly, like these ones 
• 1.25 or 1.5 inch trim head finishing screws to attach the bench top slats like these (you could potentially use up to 2″, if your top planks are thicker than 0.5″)
• A power drill
• An electric saw, such as a circular saw or miter saw (unless you have the lumber pre-cut to size at the hardware store, or feel like taking on this project with a hand saw)
• Measuring tape
• Optional: a carpenter square, to help you keep everything straight.
• Optional: a wood sealer, such as this non-toxic Garden Seal or Hope’s Natural Tung Oil

INSTRUCTIONS

1) Plan & Prep

I suggest working on a flat and level surface, such as a table, workbench, concrete patio, or garage floor to build your greenhouse potting bench. Make a sketch of your design if that helps you, and jot down the measurements.

Start by cutting the four 4×4 legs and table top frame lumber (four pieces) to your desired dimensions. In our design, the four 4×4 legs measure 28” tall, and the top frame consists of two 68” 2×4’s and two 21.5” 2x4s. We waited to measure, cut, and insert the additional table top and leg supports until after the main frame was assembled.

Note: Keep in mind that depending on how you line up your outer frame boards, the bench could gain or lose a couple inches in either direction. See the photos below to see what I mean. Most 2×4” boards actually measure 1.5” by 3.5”. So, if you cap the ends of your longest boards with the shorter ones, the bench will end up being 3” longer (1.5” on each end). This matters if you’re working with a very tight space/fit like we were, and could also change how long your slatted benchtop boards need to be cut. Therefore, cut your longest board at 69” inches rather than 72” if you want to build a greenhouse potting bench that is exactly 6 feet long once complete.

2) Assemble the Bench Frame and Legs

Secure a 4×4 leg (for total of 2) at each end of your longest 2×4 board. It’s easiest to lay the 2×4” on top of the legs. See the photo below. The 2×4″ should be flush at the top of the 4×4” legs, and arranged perpendicular to one another. Use a carpenter square to make sure everything is square. Or, measure the distance between the top and bottom of each opposing leg to ensure they’re equal (straight). 

We secured the lumber together with deck screws (two screws per junction), which we find can be easily screwed in with an electric drill without making pilot holes first. Repeat with the second long 2×4” board and remaining two legs.

Next, stand the two long sides of the bench upright and attach the short ends to complete the rectangular frame. You could do this right-side up, or upside down with the frame on the ground and legs in the air. Whatever is easiest for you. Before securing the short sides, ensure that the legs are all straight and evenly spaced as you did before. Now, attach the shorter 2×4 boards to each leg in the corners.

Note: You could also do this whole operation in reverse, and attach the shorter sides to the legs first, then attach the long front and back. Your call! Truth be told, I think that is what we did. It was over 4 years ago now…

3) Add Leg Supports

Now we need to give this thing some extra stability with three horizontal supports. First, add a board between the legs across the backside of the bench, about halfway down the legs. Next, do the same on the two shorter sides. Depending on how you assembled the top of the bench, the side supports may be slightly shorter (1.5 inches shorter) than the top frame piece on the same side because you want to keep it flush with the front side of the leg. There will not be a support across the front of the bench, which leaves the underside easily accessible for storing items below your bench. Secure the supports to the legs in the same manner as the top frame. 

Variation: You could also secure the side supports along the inside of the 4×4 legs, making it easier to create a lower shelf if you so desire. This is what I did when we built our potting bench (photo below).

4) Add Benchtop Supports

Next, insert several horizontal supports inside of the benchtop frame. One support every 13 to 18 inches is sufficient, so simply play around with your bench dimensions to see what works best. For our 68-inch long benches, we added a total of four supports, about every 13 to 14 inches. Luke’s longest bench was 106″, so he added a total of 5 supports every 16 inches on that one.

Measure and cut the supports to fit the interior space between the long top boards. I always err on the long side – it’s better to have a tight fit (or have to shave a little more off) than end up with too-short of support boards. If needed, gently knock the supports into place with a rubber mallet. We installed our support pieces with the wide flat side of the 2×4” facing up. Secure them to the outer frame with deck screws (or similar).

5) Install Benchtop Slats

Now it’s time for the final finishing step! Cut your slender top boards to the same length as your benchtop. We kept ours flush with the top frame since we were after a precise and tight fit. Or, you could make them a few inches longer – with a slight overhang on each end. 

Place the boards on top and decide on the spacing you like between them. We left approximately 1 inch of space between each board. Once you figure out the layout, I suggest attaching the very front and back edge boards first, and then evenly space and secure the interior boards between them. 

Secure the top slats to the frame below using trim head finishing screws. Install the screws so that they’re flush or sunk just inside the surface of the wood, creating a smooth and snag-free finish. 

And… you’re done!

Now, all you need to do is move your greenhouse potting benches into their new home. Our benches are slightly wider than the doorway itself, so we had maneuver them in sideways and legs-first… pivot, anyone? Finally, sit back to admire your beautiful craftsmanship with a nice frosty brew! Or, homemade kombucha. Or a cup of delicious gourmet loose-leaf tea. Whatever suits your fancy. You deserve it!

I hope this tutorial on how to build a greenhouse potting bench was helpful and easy-to-follow, and will enable you to smoothly construct your very own kick-butt benches. Please let me know if you have any questions, and feel free to spread the love by sharing this post. Thank you so much for tuning in. Happy building!

Don’t miss these related articles:

• A Beginner’s Guide to Using a Hobby Greenhouse
• How to Build a Trellis: Two Easy, Inexpensive DIY Designs
• How to Build a Raised Garden Bed
• Seed Starting 101: How to Sow Seeds Indoors (or, in a greenhouse)
• How to Build a Concrete Block Greenhouse Foundation