How To Build An Indoor Greenhouse

In a grid-down scenario, we will not have the luxury of popping down to the local grocer to buy our vegetables and fresh herbs.

If you are a person who likes to garden, you will be very aware that most areas have a definite growing season. The problem is that we still need to eat even when the plants are not growing outside.

Since our homes are nicely climate-controlled, it makes sense to bring some plants inside to keep them growing during the cold and dark winter months.

Inside our homes’ walls, we can easily provide a warm, well-lit, and moist environment for the plants to grow in. This is where a small indoor greenhouse comes into play.

Why Use an Indoor Greenhouse?

There are many reasons we would want to use a greenhouse indoors, but the primary reason is that we can exercise far greater control over the conditions when we move the plants inside our homes.

Temperature, humidity, and moisture are a few of the variables that we can fine-tune to maximize our plant’s growth potential. Since the plants are inside our homes, we can also check on their condition with greater frequency.

Things to Consider

You will need to consider several factors before beginning construction:

• How much sunlight makes its way into the house. Walk around your home, examining all the areas around your windows to determine which areas have the greatest amount of direct sunlight. There are situations where there will be no good access to natural sunlight. In these cases, you will need to use grow lights in place of the sun.
• After you find a location with good sunlight or a space that you will provide artificial light, you need to determine the maximum size that the greenhouse can be.
• Once you have a location in mind and know what size of indoor greenhouse you can construct, you can determine which plants you can grow. Choose vegetables and herbs that your family enjoys and will fit the space. It is beneficial to plant some herbs that provide medicinal benefits in an off-grid or a grid-down situation.
• It would be best if you also considered whether you want to grow vegetables and herbs all the way to harvest or grow seeds for transplant later in an outdoor garden. This will have a determining effect on the size of your greenhouse and the volume of plants that you can grow at a given time.

Indoor Greenhouse Design

Once you have a plan for what plants you are going to grow, you’ll need to acquire suitable containers for them, and the size of these containers will be what you use as a template for how you are going to plan and build your indoor greenhouse.

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Be it pots, planters, or trays; you need to make sure that they will easily fit with room to grow.

What to Grow in an Indoor Greenhouse

Indoor greenhouses are often used to grow seeds into seedlings which are transplanted into gardens outside.

You can also grow a wide variety of herbs, vegetables, and even fruits as long as you have the available space to devote to their cultivation.

Please do your research before cutting any wood and plan for what you are going to grow and how you will grow it. Be mindful of the individual needs of each plant, and design your greenhouse around these needs.

Construction of the Indoor Greenhouse

The instructions that I am providing here are for the greenhouse that fit my needs and space. I used four 15″ x 8″ plastic planters as the containers for the dirt and plants.

You will have to adjust your greenhouse size according to what containers you choose to house the plants.

Determining the Size

Begin by laying out your planters in the orientation that works best inside of your greenhouse.

Once you are satisfied with their position, measure the length and width, which will be the basis for which you dimension the shelf or selves that the planters will be sitting.

Once you have the length and width, add an inch or so to each dimension to determine your greenhouse shelf cut sizes.

Tools Required

• Saw
• Drill with bits and drivers
• Square
• Carpenters pencil
• Exacto knife
• Staple gun
• Carpenters glue

Materials

• 1″ x3″ x8′ lumber available at Home Depot for $4.81USD each. I used nine boards for my build.
• 6 Mil vapour barrier available at Home Depot for $64.00 per 100 ft roll. It may be possible to find lower prices if you select alternative plastic sheeting.
• #6 x 1 ½ inch wood screws are available at Home Depot for $6.25USD for a pack of 100.
• #6 x 2-inch wood screws are available at Home Depot for $5.97USD for a one-pound box.
• Small hinges are available at Home Depot for $2.18USD.
• Staples are found at Home Depot for $13.64USD for a pack of 1000.
• Planters are available at Home Depot for $5.18USD.
• Soil can be found at Home Depot for $8.97USD.

If you had to purchase all these items in the quantities required to construct the indoor greenhouse I built, it would cost around $160USD.

It took me a little less than two hours to design and build this greenhouse. The cost and time your greenhouse will take may vary.

Building the Shelf

#1. I started by cutting the material for the shelf. The inside dimensions were made to match what I determined them to be during the design phase. In my case, I cut five pieces at 33 inches and two pieces at 18 inches.

#2. I test-fit the cut pieces before securing them with screws and glue. In this case, I chose to use three cross braces to support the planters.

#3. I made sure to place the planters inside of the shelf to confirm that they will fit appropriately.

#4. Once I was happy with how everything fit, I glued and screwed the shelf together.

Building the Sides

#1. To achieve the height that I wanted, I cut two pieces of the 1×3 lumber in half to give me four 48″ uprights.

#2. Knowing that my shelf width is 18″, I spaced my uprights so that they were parallel, square and 18″ apart.

#3. To determine the angle of the top for my greenhouse, I laid a board across the two uprights until it was sitting at an angle that I found agreeable. I made sure to leave space where the cross member and the rear board meet to accommodate the greenhouse door.

#4. I then marked the cross piece where it met with the uprights, which are now my cut lines for the upper cross members.#5. I cut the cross members and tested the fit. Given the boards’ width, I had to drill holes approximately halfway through the uprights’ width so the screws would have less material in which to drive through.#6. After drilling, I glued and screwed the upper cross-members in place.#7. I glued and screwed an 18″ lower cross member about 3 inches from the side pieces’ bottom.

Putting it all Together

#1. The two side panels are connected at the top rear by two boards that, in my case, measured 34 ¾” long. I glued and screwed them in place, forming an ‘L’ shape.

#2. I installed the shelf at an appropriate height, gluing and screwing it in place. Always check the height before continuing and make adjustments as needed.

#3. I attached more cross-bracing on the bottom and at the top front of the greenhouse.

#4. With the greenhouse frame now complete, I placed the planters inside to check the fit.

The Door

Constructing the door was very straightforward.

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#1. I cut two boards at the top opening’s full width and two more boards that will fit in between these longer boards once installed.

#2. I had to drill holes to accommodate the screws again.

#3. I made sure to test fit the pieces before gluing and screwing them together.

Wrapping the Greenhouse

#1. I cut a piece of vapour barrier long enough to wrap around the greenhouse, and then I loosely wrapped it around the greenhouse.#2. Starting at one corner, I folded a bit of the plastic over the top opening’s edge and stapling it in position.

#3. I then continued in this manner around the perimeter of the greenhouse. I had to cut and trim the plastic at the interior corners as I went around.

#4. Once the perimeter was secured, I flipped the greenhouse upside down and cut the plastic at each corner so that each side of the greenhouse had a plastic section that could be folded and secured to the shelf’s underside.

Related: How To Grow Suspended Food Indoors

I made sure each of these sections was long enough to cover the bottom of the shelf fully.

I folded the four plastic sections one at a time over onto the bottom of the shelf, securing and trimming as necessary.#5. I laid the door down on a section of plastic and folded, trimmed and stapled to get a snug fit of plastic around the outside surface of the door.

#6. Then I secured the door in place with hinges.

What’s More

Place the greenhouse in position and place the dirt-filled planters inside. It is a good idea to include a thermometer with a hydrometer to monitor the greenhouse conditions. Plant and water whichever seeds you see fit.

Building an indoor greenhouse may seem like a daunting project to undertake, but it is not difficult.

For a few hours of your time, you can provide your family with food during the cold winter months and give your plants a nursery in which to get the best start at life before moving to your garden.

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