Green Wall Construction

The Living Wall Construction Guide

Why I decided to build a living wall

I was inspired to build my Living Wall after reading a book by Patrick Blanc and seeing the photos of some of his projects on his website.

Patrick Blanc is a tropical botanist that has traveled the world and studied tropical plant habitats. He used his botanical knowledge to create a way to grow plants that resembles their natural habitat and eventually came up with his original concept called Mur Végétal or The Living Wall. For this project, I have followed his initial design with very few deviations.

Here's a link to the photos of the Patric Blanck's living room that was the inspiration for my project. Patrick Blanc's Wall

Advantages

I decided to build my green wall for the following reasons.

Root Growth

A living wall creates very similar conditions to the native habitat of most tropical plants.

Two layers of felt create an ample growing space for the roots so that the roots aren't confined to a pot or container. With some of my plants, the roots are in excess of 5 feet and they are still growing longer! Larger and healthier root systems make plants more resilient, which sometimes results in my plants growing faster despite less than optimal conditions.

Watering

Because the entire set up is automated, it allows for greater watering consistency so that the plants receive the exact amount of water at the exact same time every day. Additionally, it allows me to go on trips and not worry about my plants.

Root Aeration

Plant roots require air to breath in order to remain healthy. When growing plants in pots, it is very easy to over water the plants and essentially suffocate the roots. In a green wall, plant roots grow between two layers of synthetic felt and receive the right amount of water and air, which allows the plants to grow faster and remain vigorous.

Air Humidity

The wall creates its own microclimate, in which the felt and the plants evaporate water and plant leaves "trap" some of that humidity, creating a more optimal growing environment for most tropical plants.

Substrate

When growing plants in pots, one of two things usually happens. The plants either outgrow the pot or the substrate breaks down and the plants have to be repotted. In a living wall, the synthetic felt doesn't break down and, if the wall is big enough, it will be years before the plants will outgrow the wall.

Space

The green wall allows you to save space.

First of all, it utilizes vertical space that would be left unused otherwise. Second, not using individual pots and growing plants together actually saves space as well, because some of the smaller plants can be grown in the gaps between larger ones.

Aesthetics

Even though I like tropical plants and enjoy growing them, a room cluttered with multiple plant pots doesn't look aesthetically pleasing, at least in my opinion. A green wall, when properly designed, looks like a piece of rainforest, and seems a lot more aesthetically pleasing than a clutter of pots.

Although growing plants in a green wall has many advantages, it's not the ultimate solution for every situation. Ultimately, wether you want to grow plants in pots or in a green wall set up is a matter of preference.

Construction

In this section you will find a detailed description of how I built my green wall. At the end of this section, you'll find a list of materials and tools that I used for the project and their approximate cost.

In a nutshell, the design consists of a metal frame, PVC sheet, two layers of Polyamide felt, a reservoir, and a simple irrigation system running on a timer. It is a fairly simple set-up that is exceptionally durable and versatile.

Planning

Before going to the hardware store or ordering the materials online, it might be a good idea to measure the area where you're planning to install the wall, create a simple drawing, write down all the dimensions, where the screws are going to go, etc. If you plan everything thoroughly, it will save you time and money so I would recommend spending some time on it.

The Frame

I built the frame from 3.6" metal studs available at most hardware stores. They are easy to cut with aviation snips and I used a stud crimper to connect the pieces together.

Here is a simple diagram of the metal frame. You'll notice that I added several horizontal pieces for structural reinforcement. I did it because my wall was going to be pretty tall 10'. If your wall is shorter, you may not need to add them at all.

PVC Sheet

I ordered a 3 mm thick PVC Sheet instead of a 10 mm thick one by mistake. Although it works fine, I have to be careful when I staple things to it to make sure the sheet doesn't crack. So, I would strongly suggest buying a 6 or 10 mm PVC sheet instead. The nice thing about ordering from places like Laird Plastics is that, for an extra $20, they can cut your plastic sheet to the specified dimensions.

Once I got the plastic sheet, I attached it to the frame using self-drilling roofing screws. The reason why I selected them for this project is due to the fact that it is easy to drive them though the metal and they have a rubber washer that is supposed to keep the water from entering into the hole.

To make it easier, I pre-drilled the holes in the PVC sheet beforehand.

Also, to make a tight seal around each screw, I put a dab of aquarium silicone around each hole before inserting a screw.

It is important not to put screws in the bottom portion (about 24") of the sheet so that you can bend it away from the frame and insert the back of the fish tank between the metal frame and the PVC sheet. That way the reservoir will capture the excess water from the wall. The PVC sheet should have enough flexibility to allow for that.

LED Grow Lights

For this project I used grow lights from theorchidhobbysit.com. I've used grow lights from www.theorchidhobbysit.com before and they work really well. The lights are inexpensive, durable and they produce the kind of light that looks like daylight to the human eye, which was important to me.

The Fabric

Patrick Blanc uses 3 mm needle punched polyamide felt (containing 0 percent wool) in his projects. In my research, I couldn't find too many manufacturers in the United States that make felt of suitable quality. Most of the manufacturers' products that are designed for green walls, specifically in the U.S., are actually too dense and prevent the roots from growing into the fabric. Also, some of the products available are hydrophobic and actually repel water instead of absorbing it.

Although many companies specializing in green wall construction have greenwall kits available, I decided against them because their kits have felt pots sewn to a felt sheet. The reason why that is not ideal is because it doesn’t allow the roots to grow freely and requires the use of a substrate. In Blanc’s design, the root's growth is not restricted, as they grow between two layers of felt stapled together.

You might be tempted to add some substrate to the wall. I've seen some people build the wall and add sphagnum or make pockets in which they add Leca. They do it because they are worried that plants without any soil will die or not do well. I've actually tried adding potting soil, sphagnum and lecca and every single time I ran into significant problems. So, even though it might be a bit scary to take your expensive plants, wash away all dirt from the roots, and insert them into the felt with nothing else, I would strongly suggest doing just that. In the next article I'll talk more about installing plants into the wall.

I opted for 3 mm Polyester felt from Mood Fabrics because they don’t have a minimum order quantity and I didn’t have to buy more fabric than I actually needed. It seems a bit denser than what Blanc uses in his indoor projects, but it works fine. After I completed my wall, I found the perfect product on Alibaba.com. The difference between what I used and the felt that Patric Blanc uses in his projects is that it is less dense and it is needle punched to allow the roots to breathe more. The polyamide felt, sold on Alibaba, seems almost identical to what Blanc uses in his projects. The advantage of the material that I used is that it retains more water, which is a good thing in a dry Midwestern Climate.

Once I got the felt, I measured and cut a piece that was the length of my wall and twice the width.

I used a staple gun to attach the felt to the PVC sheet. It's important to staple the first layer first, and then staple the second one.

I would then take one side of the fabric and align it with the edge of the PVC sheet, then staple it evenly throughout until it looked nicely secured. After that, I would fold it over and align the other edge with the edge of the PVC sheet and do the same. When starting the second layer of felt, first align its edge with the edge of the first layer of felt, then measure 1 inch from the edge and start stapling. The reason why you want to start stapling the second layer an inch away from the edge is because it will allow you to add the irrigation tube between the two layers later.

Reservoir

When building Green Walls many people build a reservoir from 10 mm PVC sheets. In my case, I found it was cheaper and more practical to buy a 10 gallon aquarium from Petco and just line it with black PVC sheets on the outside to make it match the rest of the wall, and to prevent algae from growing inside the tank.

After a few months, I discovered that a 10 gallon tank was too small for my size of wall for two reasons.

First, for the size of my wall and the number of plants in it, the 10 gallons of nutrient solution wasn't enough, as the plants would use up certain nutrients too quickly.

Second, the water would evaporate too quickly, and even in the colder winter months it would only last about a week before the pump would be halfway out of the water (which could potentially damage the pump). After six months, I switched to a 20 gallon tank ($40 at petCo.) and it now lasts me up to 3 weeks.

Before using the tank, make sure you fill it up to the top on a level surface and check for any leaks. While leaks are extremely uncommon, the first tank that I bought did have one.

The Irrigation System

The beauty of Mr. Blanc’s design is in its simplicity and reliability. The irrigation system consists of a pond pump, and, a piece of tubing that runs to the top and horizontally across the wall in the shape of an upside L. Additionally, I would suggest adding fine aquarium mesh around the pump to prevent the irrigation system from clogging.

Here is a simple diagram of the irrigation system.

Here is a picture of my wall before I installed any plants on it. You can see that the hose goes up and then across the top section of the wall. (I drew black lines to help you see the outline of the irrigation system better)

My friend Hector decided to build his green wall. In the picture above, you see the frame and the irrigation system. Instead of piercing the hose, he used individual emitters that he inserted into the hose and used an aluminum L bar to build a metal frame.

The pump

I used a submersible pump from Harbor Freight because it was one of the cheaper options.

You could also buy one at a local hydroponics store.

The most important thing to consider is the Maximum Head Lift, which is the maximum height to which the pump is able to lift the water. You want the number to be at least a foot greater than the height of your wall. In my case, the wall is 10 feet tall, so I chose a pump with the head lift of 11 ft.

Connecting The Pump To The Hose

After I purchased the pump, I measured the outside diameter of the nozzles that come with the pump and and was looking for a hose that would fit. I ended up buying a 3/8 inch hose from Lowe's. My pump didn't come with a suitable connector so I had to purchase that as well. Most hydroponics pumps will come with several different hose connectors.

The Hose

I used a ⅜ clear hose from Lowe's for my project. A better alternative would be to use a rubber hose specifically designed for hydroponics.

I didn’t use an elbow connector and instead I just bent the hose roughly 90 degrees at the top. I would suggest using an elbow connector at the top instead and secure it with two metal hose clamps. The horizontal portion of the hose is perforated. To do that I used an old file with a sharpened end. I used a cigarette lighter to heat it up the file before piercing the holes. Also, I drew a horizontal line on the hose to mark where the holes would be. The holes should be spaced out about 6 inches or so. Finally, I filled the top of the end of the hose with silicone. Alternatively you could use a hose stopper and a hose clamp.

Assembling The Irrigation System

The hose is placed between the two layers of the felt and secured in place by stapling around it on both sides. At the top I did the same, and I stapled the hose below and above it all the way across. That way the hose is kept in place and doesn't move around on its own.

It is very important to orient the holes in the hose facing the wall, otherwise it will spray all over the room. Once the hose is installed, I waited until the wall is finished to attach the pump.

Mounting The Structure To The Wall

I used one screw on each side to attach the structure to the actual wall. This was sufficient and the structure is pretty sturdy. After I attached it, I would lightly pull on the bottom part of the PVC sheet to create about an inch gap between the sheet and the frame to insert the back wall of the fish tank. this way the sheet and the felt are both in the tank. (see diagram for explanation) Now is the time to attach the pump. If the hose connector is barbed, you might choose not to use a hose clamp. It’s ultimately up to you. Just make sure it is tight enough.

After the wall is completed, fill up the tank with water and run the pump for a few hours. In the meantime look behind the wall (through the opening in the metal studs.)and check for leaks. It is important to run the pump for a few hours at first so that you can flush everything, and get rid of any residual chemicals from the felt and the silicone.

Materials & Tools Required For The Project

Here you will find a list of all the materials and tools I've used for the project. I am also including current prices (February 2021) so that you can have an idea of how much it would cost.

Materials

Product/linkTotal Cost

4 Metal Studs from Lowe's. $17.52

Roofing Screws from Lowe's $10.98

Aquarium Silicone $11.99

3/8 Vinyl Tubing from Lowe's $9.28

Polyester Felt from Mood Fabrics(I used 4 years $35.96

Submersible pump from Harbor Freight. $49.99

Hydroponics Timer 8.69

20 gallon fish tank from Petco $40

12 mm thick PVC sheet (Sheet dimensions: 48" x 96") from Eplastics. $155.45 + $20 for cutting

If you're in the U.S. , you might find it cheaper at a local plastic manufacturing store like Laird Plastics. For an extra $20 most places will cut it to size for you. I would also suggest cutting two pieces with the dimensions of about 1" by 96" (or the length of your green wall) and attach them on each side with silicone. They will protect against the water spilling on the side. (Note that I didn't include the cost of shipping because I purchases it localy)

Hose connector from Lowe's (connects the hose to the pump. You may or may not need it depending on what nozzles your pump comes with. $3.58

Total amount: $363.42

Tools

A Stud Crimper is used to connect studs to each other to build a frame. $20.89

Hex Nut driver $2.48

Screw Driver $7.98

Electric Drill$19.99

Drill Bit Set . . - . $3.99

Staple gun (comes with enough staples to finish the project)$8.99

Snips for cutting metal studs 11.99

Paint scraper for cutting the felt $1.48

Total amount: $77.79

Grow Lights

This section is optional as depending on the location of your wall, you may not need the lights at all.

LED Grow lights form www.theorchidhobbyist.com are great. You might need several of them depending on the size of the wall $34.99

I've used this Aluminum bar to make the light mounts. I screwed them directly to the stud frame. $6.99

Total amount: $41.98

If you have followed these steps, your wall is now complete. Although you might be tempted to buy the plants and install them at this point, I would suggest reading the next two posts so that you can avoid certain mistakes, and ensure the long term success of your wall.