Mini Greenhouse DIY

Updated: May 6, 2021

Even small greenhouses can be expensive. Here is a DIY project to solve your gardening needs and won't break the bank. Depending on what you have on hand, you can finish this project very cheaply. All in all, I spent a total of $6.99. The approximate project time was roughly 4 hours, which includes the time it took for the paint to dry.


Having a mini greenhouse is useful for many reasons. It's a great way to start multiple plants/flowers growing that may have different soil requirements in the same space. It allows you to grow plants year-round. You will also be able to protect plants from harsh winters and frost.


When Your Sister Gives You A Dirty Old Window



My sister-in-law arrived one afternoon with this old window in tow. This made my day even though I had no idea what I was going to use it for at the time. I'm not sure exactly where it came from but I suspect it may be a window from a house that my Dad tore down a few years ago. In spite of its appearance, it is surprisingly very sturdy and in excellent condition.


"Whatcha gonna do with this old thing?"


I've been in the process of starting some plants indoors and having some difficulty due to inadequate sunlight. The windows of my house are thankfully, positioned in a way that the sun doesn't shine directly in the house. Which is great for temperature control, the house stays nice and cool year-round. However, for growing plants, not so good. On top of that, I don't have a lot of electric outlets either, at least not in locations it would be convenient to set up growing plants. So grow lights is not something I can utilize right away. Outside would be my best option and that's when I remembered the window.


A mini greenhouse would solve my dilemma. I decided on a simple box style using the window as a lid. I've seen similar things like this but they are pricey, I figured I had almost all of what was needed and could do it myself a lot cheaper. This idea is versatile in many ways. You can place it anywhere you want it and, because it is small, you can move it from location to location with ease. You can make it a full box if you want. I opted to go bottomless so that I can use the soil underneath if I choose to. Being a woman, I love options. Also, at times I am not starting new plants, I can place the box over existing plants to protect them from cold weather and/or frost.


Tools You'll Need

  1. Drill - and drill bit, not sure of size exactly, one for use with 2" screws

  2. Window cleaner

  3. Paper towels

  4. Screws - 2" to 2.5" depending on the thickness of the wood you are using. I used eight 2.5" screws and twenty-four 2" screws

  5. Hinges - depending on the size of your box (I used 6)

  6. Screwdriver

  7. Approximately 9' of wood

  8. Caulk

  9. Paint - outdoor type - Also a paint can opener tool & stir stick

  10. Window

  11. A good size old cardboard box or newspapers (optional)

  12. Tape measure

  13. Saw - preferably electric

  14. Sander - (optional)

  15. Paintbrush - a 2" brush will work fine

"Anyway, let's get to it".


The first thing I needed to do was clean the window. So I went to work with some Windex and paper towels until it was crystal clear, pretty much. *It is important to note that old windows made prior to 1976 may contain lead paint. So don't do any sanding without a proper respirator mask and protective equipment. I myself, have no intention of fooling with sanding the window for this project. This isn't a professional job, just something I am adding to my yard. It doesn't need to look perfect. It will look just fine being painted over. I just scraped off loose the larger chips so the paint would hold better and let it go with that.


This baby will be outside in the weather so the glass panes will need to be re-caulked. This will protect it longer and weather-proof it. I caulked every pane on both sides. I tried my best to do a nice pretty seam but...you know how it is...things happen. Just go slow and steady and keep some paper towels handy. Don't worry about getting it on the wood so much, it will be painted over anyway. So I am not an excellent caulker, not the end of the world. I got the caulk where it needed to be and then I took my finger and smoothed it out making sure to fill any gaps. It's not great but looks a little better. I made a nice, sorta wide, seam. This is one reason I didn't need to use painter's tape on the panes. The caulk line made an adequate barrier so all I needed when I painted was a steady hand.



Let's Sling Some Paint


This won't be a too messy job but you will want to lay something underneath to protect your yard or the surface you are painting on. I broke down an old cardboard box to lay it on and went to it. I started with the window and painted on two good coats on the first side and let it dry. While that was drying, I went about constructing the box (see below). After the first side was dry, I flipped it and painted two coats on the other side. Except for my sloppy caulk job, it looks like a new window.



"Coming right along"


While the window drys, I took out my tape measure and measured the window. The width was 27.5" and the length was 28". I headed to my woodpile and found a couple of very nice planks. I'm not sure exactly what kind, I'm guessing oak because it is very, very hard. I cut it to size with an electric hand saw and then I used my sander to clean them up a bit. I'm not sure what that white stuff was but it didn't take much to sand it off. I didn't do a 'full on' sand job, just enough to make them look a little better and so they will hold the paint better.



"Let the good times roll"


Alright, now let's screw this baby together. If you have an excellent drill and maybe use softer wood, you'll probably have a better time of it. In my case, the wood I used is very, very hard and my drill is mediocre. I drilled the holes out first and then turned the screws with a screwdriver. I probably could have screwed them in afterward with the drill, but this way I could assemble it as I go without the need to keep changing the bits out. I used two 2.5" screws on each side. They seem a little long for this but the wood I used is an inch thick so if I used 2" screws, they would barely go in all the way through. After the window finished drying I set it on the box to see if it was going to fit properly.



"Ah, very nice!"


I set the window aside and went to work painting the box. I applied two good coats all around, inside and out then allowed it to dry. After that, it is time to attach the hinges. Since I had everything I needed for this project, except hinges, that ended up to be the only actual purchase I made. I bought a pack of 6 for $6.99. The way I put the box together, it left a little almost an inch where the window comes to the edge of the wood on the backside. This was actually intentional because of how I wanted to mount the hinges. Instead of attaching them the normal way, straight down the back, I thought the window might be too 'top heavy' and pull loose, eventually. Since the window is so heavy, I used all 6 hinges and mounted them to the top of the box and the side of the window (as shown below). This way, the top of the box supports the window and the window is able to stand its own weight and is properly supported without having to be propped up. Again, I pre-drilled the holes and then screwed in the screws with a screwdriver. The hinges come with very small screws, that just ain't gonna cut the mustard. I used my own screws. I chose 2" screws for the hinges.


A Job Well Done


Even if I do say so myself. I found the perfect spot for it. There is a place near my backdoor that grass is having a tough time growing so this covers it nicely. Like I say, not having a bottom, I can move it anywhere if I want to cover a plant during a frost. I took some garden bed liner to keep any weeds from coming through and tacked them down with garden nails, they are in a 'U' shape. I set a few of my flowers I started in containers inside and patted myself on the back.


Check It Out


I hope you enjoyed this project. All it takes is a little imagination and necessity. Oh, and one more thing; Buster has been keeping an eye on his cat grass 'Paw Patch'! It's coming in nicely. He can't wait to nibble on it and has been probably sneaking a taste when my back is turned. Thanks for reading and have a terrific week!



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