Re-purposed Windows- DIY Greenhouse

Updated: Mar 30

If you don't know me, I'm a Florida girl, transplanted to the arctic tundra of NY.

It was never my plan to stay in NY forever when I made the move, but as life would have it, I met and fell in love with a native Long Islander, and the rest, as they say, is history.

My husband (boyfriend at the time), promised me a greenhouse to get me through the long NE winters.


It took years before we made that a reality, but he kept his word!

When we initially set out to build a greenhouse, I had seen pictures floating around on the internet of greenhouses built from re-purposed, antique, and salvaged windows and doors. I fell in love with the idea, but really couldn't find a comprehensive step by step plan for building my own.


It's a project you guys. Better that you know that going into it, lol. However, I'm in love with the finished product, and it's made it through two winters so far. With that said, let's get into the nitty-gritty.

Materials

Windows and doors

2" x 10" lumber for decking and floor joists

4" x 4" pressure treated posts for posts

Concrete

Concrete 8" tubes

Metal concrete anchor post bases

Floor Joist Hangers

Roof Rafter Hangers

3" outdoor decking screws

2" outdoor decking screws

1.5" outdoor decking screws

Paint

Ribbed Clear Poly-Carbonate Roof Panels

Ribbed Foam Closure Strips for under poly-carbonate panels

Self Drilling, Galvanized, Sealing Screws for roofing panels

Clear Silicone Sealant for roofing panels

Deck Panels

Window Vent Openers if you have opening windows in your cupola

Step One

You're going to need windows, lots of them, and at least one french style door. Have an idea of how large you want your greenhouse to be going into it, so that you can get the right size windows.

I knew going into it that I wanted my finished greenhouse to be approximately 10' x 10'.

I started scouring craigslist, garage sales and more in the search for windows and doors. I was able to find some for free, and paid a minimal amount for others. Once I had several windows I started drawing out how I could put them together.

I'm big on symmetry, so I tried really hard to find multiple windows and doors in the same sizes. You don't HAVE to make your greenhouse symmetrical, just know that it will make things easier for you if you do.

The front and back of my greenhouse are opposites, but the sizes are the same, which simplified things. Each individual side is different from the other, but they are symmetrical individually. Using my wood frames and some filler pieces I was able to make up for any difference so that the sides ultimately ended up being the same sizes.

You can get a feel for how to potentially lay yours out by looking at how I did mine.

This is the front. The back basically mirrors it. I can't get a great picture for you guys because there's only about 3' to the fence.

These are the right and left sides. As you can see, each individual side is symmetrical unto itself. You may have to get creative with your layouts. Once I had several windows and doors and had a basic layout drawn up, I began to look for specific sizes that would fit into the empty spaces I had left.


Step Two

The next thing you need to figure out is where you're going to build your greenhouse. You'll want a space that gets good sun, particularly during the winter months. Here your steps may diverge slightly from mine, depending on how level the area you intend to build is. Our area was extremely un-level, with lots of large tree roots beneath, so we opted to build up, on piers creating a crawl space of sorts beneath, and adding on a porch in front. You could skip the porch part if your greenhouse can sit on or close to the ground.


Another thing you need to consider from the very beginning is if you want your greenhouse to have electricity. We wanted it for light, and to have the option of plugging in fans, heaters, and propagation mats. You'll need an electrician to run the underground wire for you, or be handy with electricity.


Step Three

Stake out the dimensions of your greenhouse, making sure it's square. This is legitimately one of the hardest things to do. Being off by just the tiniest amount can throw your entire greenhouse out of whack, so take your time with this part. If you don't know how to square your stakes, there are tutorials online that can help you!


Step Four

Dig a hole for each of your posts. Depending on the size of your greenhouse, you may have 4, or more. We opted to do a total of 6 because we have a porch attached to the front of ours.


Depending on where you are you'll need to dig up to 3' deep to get below the frost line. We used concrete form tubes to create concrete pilings to support our structure. Pour concrete into each tube. You will want to use concrete anchor metal post bases when you pour your concrete. This will give you a firm base to attach your wood posts. This link shows you what to look for.


Make sure that you place these metal post bases in the proper location. You will want your posts to sit 1.5" inside your final floor size each. This will allow for the 1.5" additional that will be attached in step six. Allow your concrete to cure.


Step Five

Once your concrete has cured, you will add your posts.


Remember, each post should be placed 1.5" inside the final size of your floor. For example; If you are going to have a finished 10' x 10' floor, each post should be 1.5" in from that point. When measuring from the OUTSIDE of one post to the OUTSIDE of the opposite post, you should be 3" shy of 10' in total.


We used pressure treated 4 x 4's for our posts. This is the part where you will make sure you're level as well, if you've been working off an un-level surface.


We started at our highest point. The first post was cut to the height we wanted our floor to be at. We then worked off the height of this post to make all of our other posts level with this one. This means that some posts will be longer than others, but the top of all your posts should be level. We used a line level and a thick line to make sure.


Step Six

You will now create the outside box of your floor, where you will be attaching your floor joists to.

We choose to use 2" x 10" pressure treated wood for this. You'll begin by attaching a 2" x 10" piece sideways from one post to the other, on the OUTSIDE of the post. You'll want to use 3" screws for this. These are the screws we used. They're not inexpensive, but they work really well and are made for these types of applications. They also don't strip easily, which is a huge plus in my book! You'll want to repeat this all around the outside of your posts. You'll want to start on one side and cut each piece long enough to stick out past ONE post, so that the next piece sits flush against it and work your way around. This will help ensure that your final floor is the correct size.


For example; if your total floor size is going to be 10' x 10', then your posts should be 9'-9" apart. Each of your 2" x 10" pieces should be cut to 9'-10.5". This is the extra 1.5" that you'll be placing the next piece up against.


Step Seven

Now you will begin adding in your floor joists. We use 2" x 10" pieces of lumber for this as well. We really like using joist hangers for this because it really simplifies the project and makes for strong attachment points. We used this kind. You'll want to place your floor joists no more than 16" apart. Measure your total space and mark out where each floor joist should be placed on both ends so that it's easier to work quickly.

Step Eight

Once your floor joists are all hung, the next step will be to actually add on your floor. We used 1/2" ply wood for this inside the greenhouse, and we used deck boards for the porch area so that water could flow through.


Step Nine

Now you will begin building each wall. Walls are easier to build laying flat and then lifted into place.


We used 2" x 4" studs for our walls, but we doubled up our studs in each corner, and we doubled them up in other areas as well depending on the span. You'll be framing out the space between each window/door you'll be placing in between, so check and double check your measurements and make sure that your windows etc will fit in their intended space.


In some cases, you'll want to use a thin strip of 1/2" plywood sandwiched in between your 2" x 4"s. Doubled up 2" x 4"'s actually measure 3" x 3.5" because most wood is not a true measurement. If you're building a corner, you'll want to sandwich that 1/2" piece of ply in between your studs, so that your finished corner is a square 3.5" x 3.5"


I highly suggest painting your floor at this point, as well as all your studs. It's easier to paint each piece as you go instead of waiting until the end and then having to work around obstacles.


Step Ten

At this point if you haven't already prepared all your windows and doors, this is the time to take a break and do that. We used a lot of old windows, some with many layers of paint and dirt on them. We spent days scraping and sanding old layers of cracking paint. We also used clear window sealant to reseal some of our windows. Some of them had cracked wood, so we also spent some time repairing the wood. Then we cleaned them all, and painted them all BEFORE placing them. It's so much easier to paint them laying flat! Far less dripping.

Step Eleven

Now you get to start putting your windows and doors in place and this is when it REALLY starts to resemble a greenhouse!! For this part we took long finished pieces of wood and created frames.


Working from the outside of the greenhouse, we first attached a 1" x 6" piece of wood to the studs along the top horizontally. All the way across from one end to the other.

We repeated this on the bottom as well, and we did this on all 4 sides (make sure you don't go across the bottom of your doorway!

Then we attached vertical pieces. We made sure that the vertical pieces were wide enough to overlap the studs on either side.

We painted all these pieces as well.


Step Twelve

Then we added the windows and doors into their respective places from the inside. We ran a bead of sealant along the inside of each frame, and then placed the windows up against the flat outside frame pieces. Then using 1" x 2" pieces of wood, we sandwiched each window in place using screws.


Step Thirteen

Once every window was properly placed, we used expanding foam and sealant to fill any gaps we found where cold air or insects could enter. Then we touch up our paint.


Step Fourteen

This is where things get far more tricky. The roof!

There are A LOT of different roof options you might choose to go with.


You'll want to consider pitch, particularly if you're in an area that receives a lot of snow.

You'll want to consider the fact that the lower your pitch is, the more hot air will be trapped inside. This is GOOD in the winter, but it can utterly fry your plants in the summer.


We complicated things for ourselves by opting to go with a doubled roof. It resembles an elongated cupola of sorts. The windows inside this top portion open up automatically when it reaches a certain temperature, which helps cool things down a bit in the summer. They stay closed in the winter.

We weren't able to find plans for building this type of roof anywhere, so we had to improvise. This led to lots of planning, drawing, research and heated discussions about whose ideas were better, and whether we would end up with a collapsed roof, lol.


Depending on if you choose to go with a simple A frame at this point or if you want to recreate what we did will alter what steps you take next. If you're going with an A frame, continue to step fifteen.

**If you want to create a look similar to ours, then skip down to step sixteen.**


Step Fifteen

For A frame roof construction. Choose your pitch. There are tons of handy roof pitch calculators online that will help you know how to properly cut your roof rafter angles. Your roof is not going to be holding a great deal of weight, so using 2" x 6" lumber for this part is sufficient. To give you a basic idea of how you'll want to create your rafters, imagine that you are going with 45 degree angles. This means each end will be cut to 45 degrees. You can use flat metal plates to join the two center pieces where they meet. You can use ones like this. Or you can create some out of spare pieces of plywood like we did. Check out the picture.

On the bottom edges where your rafters meet the top of your wall, you can use these. You can adjust the angle to make them work for your pitch.


You'll want to make your rafters no more than 16" apart, just like your floor joists.

You'll want to cut short stringer-like pieces, or blocks to place in between each rafter at your top angle so that you have a continuous pitch. You'll also want to cut and place blocks at staggered heights between your rafters on each side. Depending on the total length you'll probably want at least two blocks in between each rafter on each side.

**You'll now skip ahead to step nineteen.**

Step Sixteen

For cupola like construction. You will first want to decide how wide you want your cupola to be on the inside. Let's say you choose 18" wide. Both in the front (above your door) and in the back center of your greenhouse you'll measure 9" in each direction (for a total of 18"). This will be the farthest point that your first (lower) roof will come.


You're going to need two pieces of lumber that run the length of your greenhouse. Even better if you can do 4, sistering 2 on each side. The rafters to your bottom roof will come up to or sit on top of these beams, and it will also help support the studs between your top cupola windows. This is a point where we made a mistake, and if we could re-do it we would have gotten beams that were the correct length. Instead we sistered shorter beams, and I believe it compromised the stability of our greenhouse. We ended up adding some additional posts on the inside in order to brace/stabilize these beams.


Now you will want to build up the center on each end. We didn't have a very steep pitch for our bottom roof, so we simply laid a flat piece of 2" x 4" on the center of each end as shown in the picture above and screwed it into our top plate. Then we rested our long beams perpendicularly across it. Using additional pieces of 2" x 4"s we sandwiched each perpendicular beam. You can see this in the picture above as well.


If you used a total of 4 beams running the full length then you can skip this part. If you didn't, then you should now add an additional 2" x 4" beam on the inside of each of your beams. You'll want to sandwich pieces of plywood between them to achieve the proper thickness.


Step Seventeen

Now you will create your rafters for your bottom roof. Remember that each side is going to rest on top of your beams on the inside and on top of your top plates of your walls on the outside.

You'll cut each rafter to the appropriate angle, and in some cases depending on the pitch you chose, you'll end up with what looks like a right angle bite taken out of each rafter. This "bite" will fit like a notch into the top of your beams. Make sure your rafters are no more than 16" apart on center.


You'll want to cut short stringer-like pieces, or blocks to place in between each rafter at your top angle so that you have a continuous pitch. You'll also want to cut and place blocks at staggered heights between your rafters on each side. Depending on the total length you'll probably want at least two blocks in between each rafter on each side.


Step Eighteen

Now the rafters for your bottom roof are complete. You'll now need to create the studs/walls for your windows in the cupola. If these windows are going to open, then they'll need to be attached on hinges so that they may open outward. If they are fixed, then you'll be attaching them the same way as your lower windows in the main part of your greenhouse.


In our case, we were lucky enough to find the 4 opening windows we used for this portion, and simply created the other windows in order to complete the look. Depending on what you are able to find you may have to get creative in what you use for this portion. Making windows is relatively easy. One of the easier small projects within this larger project.


We attached the studs for this portion to the roof rafters below, as well as to the main beams running the length of the greenhouse. We then cut smaller 2" x 4" blocks and screwed them flat into place in between each stud for added stability.


*A note*

We didn't install the windows in this portion until after we put the roof on. It was easier to install the roof without the windows in place, and relatively simple to install them after the roof was complete.


**In order to create the rafters for the second cupola roof, skip back up to step fifteen.**


Step Nineteen

Installing the roof.

We spent awhile researching different greenhouse roofing materials. I considered glass (super heavy). I considered other options. In the end we decided to go with poly-carbonate roof panels. They cut down to size fairly easily. You'll need special screws and ribbed foam pieces to place between your flat wood studs and your ribbed poly-carbonate sheets. You'll also need clear silicone sealant to seal between your panels where they overlap each other in order to get a tight, weatherproof seal.

The last part of your roof will be installing you ridge cap. We used this one. There are a variety of options. It's easy to cut down to the appropriate size.


Step Twenty

Install the windows in your cupola area. Fixed windows will be installed like the windows in the rest of the greenhouse. For windows that open, you'll want something like these window vent openers.


We wanted to give ours a little extra flare, so we put in stained glass in some of the window panels. You can also use those stained glass window films that are self adhesive, like these.


Step Twenty One

On the front and back of your greenhouse You'll have some gaps to fill. We created templates and cut long lengths of finished wood to finish the gap above the front door, below the cupola.

Finish any touch up painting you have left.

Step Twenty Two

We decided to make our floor inside the greenhouse out of brick. We read that brick would help retain heat in the winter, and I love the rustic, old European look of it.


It was pretty easy to find people giving away brick on craigslist. We went all over the place filling up the back of our car with leftover brick. My only criteria was that they were the same height. Bricks definitely vary in size, they are NOT all the same. However I thought it contributed to the salvaged look and didn't mind having different sizes.


I did use a diamond blade on our saw to trim some pieces down a bit, particularly along the edges. I went with a herringbone pattern, but you do you. I used a fine mason sand in between my bricks once they were all laid to complete the look. You can see the difference between the picture above and the picture below. The one above doesn't have the mason sand in yet, and the bricks were still shifting around. Below I've added the sand in and the floor is rock solid now.


Make sure you put down a threshold piece in your doorway to transition to your deck boards on your porch if you added a porch.

Step Twenty Three

Add in shelves, hooks, etc for your plants, and for your gardening tools. We just used spare pieces of lumber for our shelves. I tried to paint everything to match, so that they blended in better, and I tried to line my shelves up with the grids in the windows so as not to obstruct the view.

I also added in a couple strands of big, outdoor patio lights and strung them up.

Step Twenty Four

If your greenhouse is elevated off the ground, you'll want to create some sort of skirt around the outside so that animals don't live underneath. You can use basic lattice panels for this, or you can create your own look. We decided to install leftover pieces of deck boards vertically for this. As you can see in the picture, it's not completed yet. But it gives you an idea of the possibilities.

Step Twenty Five

ENJOY!!!!!

Questions? Stuff I missed? Comment with your questions below, I'd love your feedback and I'd love to give more details if needed!







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