27 Nov Concrete thinking: How to make mod, stackable sculptures with concrete blocks

July 2022 update: We’re using some new colors and experimenting with a different (and exciting) shape of concrete block plant stands. Check out the latest post.

“What is garden art to you?”

That was the theme of the night during this week’s #GardenChat, the lively Twitter convo that happens every Monday from 6 to 7 PM PST. (Have you been? It’s a lively place to meet garden-minded people…)

That got us to thinking — and tweeting — about the ways in which Ryan and I like to add human-made flair to our yard. There’s the furniture Ryan designs, of course, and our luscious bird feeder and tuteur from TerraTrellis, which adds bold sculptural interest to our surroundings.

But these days we’ve been finding a lot of whimsy in…concrete blocks.

We constructed a sturdy platform base to support our ever-changing concrete block sculpture. The dimensions of the platform are 44 inches by 21 inches, so that the 6 x 3 grid of 8 inch-wide concrete blocks overhangs the base. Our 48-block sculpture at 14 pounds per block weighs roughly 678 pounds! Important: we made sure to level and set our platform legs into the ground with 2 50-pound bags of concrete.

That’s right: good old-fashioned concrete masonry units. Their size, shape and negative space make them incredibly versatile to use inside a garden.

Find them at your local hardware store. Concrete blocks come in many different sizes shapes and can double as planters. Got a bunch of gourds to show off? Use concrete blocks to make a deconstructed jack o’lantern. Feeling down? Build ’em up into the throne for your spectacular self! You can, and should, paint them. (Instructions and reasoning in a minute…)

Update: check out our January 2016 post on primroses!

2016 update.

Lately we’ve been using this concrete block sculpture as a tiered vertical display of some shade plants that we are tending for the Culver City balcony project that we are working on. We love the versatility of these blocks.

Frank Lloyd Wright’s Ennis House, Los Feliz, Los Angeles. Photo credit: Flickr — Willivolt.

Our use of concrete blocks was inspired by Frank Lloyd Wright, who used patterned concrete blocks extensively — most notably in his “textile block” houses like the Ennis property in LA. The inherent contrasts — the heaviness of the concrete vs. the bricks’ intricate patternwork; weather-stained cement vs. emerald trees — are robust, and right up our alley.

We’ve been moving concrete blocks around into various configurations for three years now in two locations within our garden. Our first location is beneath our citrus trees. We love the shadows that Ryan’s LED lights cast on this 40-block sculpture at night, but we’ve noticed that three years outdoors have left our blocks stained and dull.

On the right is our first concrete block sculpture beneath the citrus trees in our garden. This photograph was taken in September before the citrus lounge remodel.

Ryan’s LED stadium lights illuminate our garden and throw shadows across this concrete block sculpture at night. We also use some upward-facing concrete blocks as planters.

It is nearly impossible to clean stains off of bare concrete blocks due to its porosity. Concrete blocks need to be sealed before they become cleanable. So recently painted the forty blocks of our first sculpture a clean shade of “Rustic Taupe” to match our newly renovated “citrus room” that Ryan built beneath our orange and tangerine trees. When we brought the blocks into the new room, we configured them differently and used them to support a new bench.

Before and after painting concrete blocks. The primary reason to paint blocks is to seal them and make them cleanable. Our concrete blocks measure 7-5/8 inches wide by 7-5/8 inches deep by 5-5/8 inches high and cost $0.79 each.

Citrus lounge remodel. We’ll move around these forty concrete blocks to fit our mood. We painted each block the same color as the deck and walls in order to draw attention to the geometrical shapes.

Painted concrete blocks create a clean contrast with the leaves and blooms of our flower bed.

We painted the new bench using Behr Exterior Paint (shade: “Vixen”) to match our TerraTrellis sculpture.

DIY Painted Concrete Block Sculptures:

1. Arrange concrete blocks for cleaning. We recommend resting each block at a slight angle (atop wood slats, for example) so that the blocks are not flat against the ground when drying. We added a dropcloth and used this arrangement for painting as well.

2. Wash the dirt from your concrete blocks with a strong jet of water. We used a pressure washer. This step can be skipped if the blocks are new and clean. A scrub brush and garden hose sprayer could be substituted for the pressure washer. The cleaner the block, the better the paint will adhere and the longer it will last. We waited four hours for the blocks to dry before applying bonding primer.

3. Prime and paint the blocks. Bonding primer assures maximum adhesion of paint to concrete. We used Behr’s Concrete & Masonry Bonding Primer and Concrete & Garage Floor Paint from Home Depot for this job. Both are latex acrylic-based for easy cleanup. We used nap rollers to apply both products, making sure to thoroughly coat the inside of each block. We applied two coats of paint on top of one coat of primer. We waited a day between each coat.

The bonding primer reminded of us skim milk and applies very thinly.

Applying the primer with a nap roller.

We found that a six inch nap roller worked perfect for painting the inside of these blocks, which is very difficult to do with a brush. Each block took about two and a half minutes to paint. Forty blocks took about an hour and half! The second coat went a little faster.

4. Wait at least two days before arranging and stacking the blocks so that they do not stick together. Make sure your platform is strong and level.

Who knew a bunch of big, hulky blocks could feel so serene?

Speaking of peace and happiness, we hope your Thanksgiving will fill you up in every way that matters. Have a fun holiday — and see you on the other side of that pumpkin mousse cheesecake!

UPDATE: We brought in some staghorn ferns to warm up this outdoor room and to complement the geometric shapes of the concrete blocks. Check out our guide to mounting staghorn ferns here.