How To Build A Greenhouse in a Tiny Space

If you’ve got a green thumb, or if you WISH you had a green thumb, you’ve likely seen gorgeous glass greenhouses and wished you could have just a tiny piece of that growing capacity.

How To Build A Greenhouse

But in your tiny apartment, condo, or house, it’s impossible to grow anything indoors, and the growing season’s too short to do it outside, right? Wrong. There is a perfectly easy way to build your own greenhouse area in the smallest of spaces to start seeds in preparation for spring or to grow your own vegetables or herbs or flowers – even in a basement or on a shelf with no or little natural light. This article will help you learn how to build the perfect small-space greenhouse.

DIY Green House Building Level: Beginner Project

DIY Small Space Greenhouse - artificial light

Materials you’ll need to build a small greenhouse:

  • Grow light (discussed below), double loop chain, eye hooks
  • Timer (discussed below)
  • Seeds
  • Seed trays and lids
  • Proximity to an electrical outlet for the timer and light

How to build a small greenhouse step by step:

Size of your greenhouse

The size of your “greenhouse” need only be as big (or as small) as the grow light you choose. These are sold in 2-, 4-, 6-, and 8-bulb sizes.

More light for bulbs

While the 8-bulb grow light does have more light, it also requires more space. The 2- and 4-bulb lights are smaller, but because you’ll want to turn the trays sideways when the plants get bigger anyway, you’ll be able to grow the most if you have footprint space of the 6-bulb light.

How to install the indoor grow lights

maximum lighting in a small space

For these reasons, and for maximum lighting in a small space, we recommend the 6-bulb grow light, simply because it easily accommodates at least four trays of seeds and starts, turned sideways and lined up under the light.

opening up the grow light box

Use care in opening up the grow light box and when you remove the light itself so as to not (a) break any bulbs, or (b) dent the reflective aluminum shields near the bulbs.

Remove any protective packaging

Remove any protective packaging used for shipping. This will likely require you to remove the bulbs individually, as they are (hopefully) protected individually for shipment.

replace the bulbs by carefully grasping the bulb

You will remove and then replace the bulbs by carefully grasping the bulb with two hands and twisting until the metal pins on the bulb line up with the slot on the light frame. Slide the bulb in or out, straight up and down.

Remove the bulb protection

With the bulb out, remove protective foam, if applicable.

Replace the bulb by sliding the metal pins

Replace the bulb by sliding the metal pins into the slots and twisting the bulb gently to lock it into place. Repeat for all bulbs that require packaging removal.

DIY Small Space Greenhouse36

Pick a place that you can designate as your grow space. This could be an old table, a shelf, or even the floor. It can be in the basement (as long as it’s temperature-controlled), in a home office, or even in a mud room – natural light sources are not required for the success of your plants, due to your grow light. This tutorial uses a top shelf in a backyard shed.

double check the fit

Once you’ve identified the spot that you can grow things, it’s time to mount your grow light to the ceiling above. First, although you’ve measured it out before you purchased your grow light, double-check to make sure the light will fit your space as expected.

DIY Small Space Greenhouse - Lights

On the side of most grow lights are on/off switches, the cord, and often an outlet for linking other grow lights together. Make sure these things are accessible as you determine the mounting placement.

Your grow light comes with two metal hooks

Your grow light comes with two metal hooks attached to the ends of the light frame. Because you already know how your grow light will fit lengthwise (due to the “dry fit” placement you just conducted), you now need to determine where the hooks need to be positioned with regard to width. Measure the width/depth of your light (about 20”), then divide this measurement in half.

your growing space footprint

Use a stud finder to find the ceiling beams that most closely align with your growing space footprint. Or, if you’re lucky, simply use the exposed beams available to you in your unfinished shed. Measuring from the wall (or wherever the side edge of your grow light will hang), mark the halfway distance (about 10”). Repeat for the second beam.

Screw hooks

Use two #8 screw hooks. These are strong enough to hold up your light, but small enough to easily screw into a 2×4 ceiling beam.

Screw the hooks into the ceiling beam

Screw the hooks into the ceiling beam at the point you’ve marked. Predrilling is not required, although you can predrill if you choose. Just be sure that, if you do predrill, the hole is small enough that the screw hook has a very tight fit.

Use pliers to tighten up the screw hook

Use pliers to tighten up the screw hook. Note: The two hooks you use do not have to be precisely centered above your light; the chains that you mount your grow light on can be angled if necessary.

two screw hooks mounted securely

At this point, you should have two screw hooks mounted securely in two ceiling beams at an even distance (at least half the width/depth of your grow light) from your wall.

Attach a carabiner to one end

Attach a carabiner to one end of your double loop zinc chain, then repeat for the other chain. These chains can be purchased and cut to length at your local hardware store – each should be long enough to hang from your ceiling-mounted eye hook to your grow surface. If your grow surface is a table that is 5’ from the ceiling, for example, maybe purchase two 6’ chains (or more, if your chains don’t hang straight down). This example involves two chains cut to slightly less than 2’.

Attach a carabiner to each

Attach a carabiner to each of the wire attachments on the sides of your grow light.

use the chains

Use these chains to carefully lift your grow light. We recommend using a helper if your light is not positioned flat on the ground, as you don’t want it swinging down and breaking a bulb.

Set the grow light flat

Set the grow light flat on the growing surface so you can position yourself to safely and securely attach the chains to the screw hooks. Double check the proximity of the electrical outlet you’ll be using, to make sure the cord comes out of the correct side of your grow light. Rotate the light at this point if needed.

Place one section of your double loop chain

Place one section of your double loop chain onto one screw hook. Don’t worry about making the light level or straight at this point; that’s easily adjustable later.

Lift the other side of your grow light

Lift the other side of your grow light and secure the second chain onto the second screw hook.

Make any adjustments

Make any adjustments needed with your chain to ensure the grow light hangs perfectly flat all around.What this safe yet versatile setup offers you is the ability to raise and lower your grow lights as needed based upon your plants’ growth. It’s a simple operation that can be maneuvered by just one person, which is helpful – just adjust one chain at a time to hit the desired grow light height/distance from plants.

unable to mount the screw hooks

If you were unable to mount the screw hooks onto perfectly centered ceiling beams, your light can still hang securely and positioned well if you have some sort of support on one side, to hold it into place. We used the edge wall of the shelving unit to this end.

Run your cord to the nearest

Run your cord to the nearest, or most convenient, electrical outlet.

DIY Small Space Greenhouse- electrical part

Technically, you’re done setting up your grow light. However, we strongly recommend the use of a timer. Seedlings and starts are highly sensitive, and these timers work perfectly to keep the correct amount of light on your plants. (You can adjust the time allotments anytime.)

Simply plug your timer into the electrical outlet, then plug your grow light into the timer. Follow the instructions on your timer packaging to set the timer. This ensures that you won’t forget to turn the lights on/off during the course of your busy life, although you’ll still need to remember to water them daily.

The amount of light you choose to use depends on a number of factors, including but not limited to the availability of natural light in your small space greenhouse, the type(s) of seeds, the development of the seedlings/starts.

let you rock your green thumb

Now that your grow light is in a position to let you rock your green thumb, let’s talk for a minute about how it works in relation to your seeds and plants. Over seeds and small starts, the grow light will hang quite close to your soil (8”-12” is a good guideline for starters; try it for a day or two and see how your soil and seeds react), so you will want to adjust the chain accordingly. Just keep the light from touching your plants – never, ever should it touch any part of the plant, or it will scorch them.

Provide great lighting source

(Although the point is to provide tons of great light to help your plants grow, you need to make sure the grow light is not too close without adequate water on your soil, or it will dry out your soil and scorch the tender starts… as you can see has happened here in the middle of this geranium tray.)

Seed tray and potting soil

Grow some flowers n your greenhouse

So let’s get some flower seeds ready to grow. Fill a seed tray with potting soil. You can start your seeds in very small seed containers and plan on moving them to larger containers as they grow.

Because the seeds become plants that you’ll transition to larger containers, those larger containers will take up more space than the small seed starts.

So, in other words, a single tray of small containers for seed starts can eventually expand into multiple, even many, containers down the road. Plan ahead for your small space greenhouse’s capacity.

Plant the seeds as per planting instructions

Plant the seeds as per planting instructions. These tiny impatiens seeds, for example, basically rest on top of the potting soil and aren’t buried.

impatiens and petunia seed

For impatiens and petunia seeds, sprinkle a tiny bit of potting soil over top of the seeds.

six rows of seeds

This is one case where only six rows of the potting soil are planted for now; as the seeds grow and become too big for these slots, they’ll be transferred to larger ones. Don’t feel like you have to fill the whole planting tray.

Label your seeds

Label your seeds, particularly if you’re planting a variety of things in your tray, such as flowers and various vegetables. Many seed starts look similar at the beginning, or you may want to keep track of colors or varieties.

squeeze or spray bottle

Carefully use a squeeze or spray bottle to wet the soil of your planted seeds. Take care not to squirt the water directly at the seeds, as this can dig them up or remove them from the soil completely. A good habit is to spray water around the seed area, even when the plants start to grow. This will help roots to reach outward and get stronger faster.

Enough water for seeds

Add enough water that the potting soil is permeated, not the top layer only.

soil is sufficiently moist

When your soil is sufficiently moist, you’re almost ready to move the tray under the lights.

Place clear plastic above

Place a clear plastic lid over the seed tray. It doesn’t have to be super tight; just the standard sized clear lid over the standard sized tray. This helps to keep the potting soil and seeds moist as they work to germinate and will speed up the growing process.

check water seeds everyday

Check on (and water) your seeds every day. Under the grow light, even with the lid on to retain moisture, the soil will dry out. Also, soil can appear dark and moist when it is in actuality quite dry. Gently press a fingertip onto the soil to gauge moistness; if your finger comes up dry, then so is the soil.

Germinate seeds

Take care that you don’t over-water; this will “drown” the seed and make it unable to germinate. If the soil is moist to the touch, slightly spongy when you press your finger down on it, then it shouldn’t need much more water, if any.

seeds sprout

When your seeds sprout and are an inch or two above the soil, it’s time to graduate them to non-lidded growth. Notice how the inner plants dry out faster than the outer ones? This is because of their position directly under the grow lights, coming from all angles.

Slight drying is normal

This slight drying out is normal and not a problem, as long as you keep them watered daily. Actually, it’s a sign that your grow lights are speeding up the growth process, so embrace it!

Adjust the height of your grow light

Adjust the height of your grow light as needed; you can even raise it to water your plants and lower it when you’re done, if you like. This system is so simple and versatile.

geraniums seeds

In just a short while, your seeds will become starts, which will turn into full-fledged plants like these geraniums that are getting their third leaves.

Seeds tray

This seed tray is sitting on the shelf below the grow light shelf to show how it fits. As more trays are required to hold larger plants, they will be turned sideways on the shelf to maximized space. This is one reason the 6-bulb grow light is recommended; all parts of the tray will receive good growing light whether parallel or perpendicular under the lights.

Seeds plants

In no time at all, your seeds will become beautiful plants…which you can enjoy in a vegetable garden.

small space greenhouse-started flower seeds

Or enjoy your small space greenhouse-started flower seeds in window boxes (make these window boxes yourself following this tutorial).

red window plants design

Wherever you choose to enjoy your plants, we hope you first enjoy greening up your thumb by creating this simple, yet highly effective, small space greenhouse.