This is a brief guide on how I took some old windows from houses they where tearing down in my neighborhood and turned them into a small greenhouse in my back yard. I collected the windows over the course of a year and a half and the build took about 3 months, spending one day a week on it. I spent about $300 for the lumber for the frame and screws, caulk, latches, etc. That’s almost 10% of what a greenhouse kit would cost. The size I built was 7 ft high x 10 ft deep x 6 ft wide. But the size of your greenhouse will depend on your windows and the time you want to put into project.
Step 1: Collect Windows and Plan Two Pair of Equal Sides.
Look for old windows and save every one you get. After you have many, lay them out and play a game trying to make two pairs of “walls” both the same height. Two to three inches won’t matter as you can cover the difference with wood. Smaller holes will need to have glass cut for them or filled with something else. Keep in mind that one end will need a door and the other a hole for a fan.
Step 2: Create a Frame
Using the windows you chose as a guide, construct a frame for each wall. Use good lumber for this, as it is the structure that holds all the weight. I used all 2 x 4s for the studs and 4 x 4s for the corner posts. Choose a length that allows at least 14″ of the stud to be placed in the ground for support.
Step 3: Brace Walls
Step 4: Make the Foundation Secure
Step 5: Screw on Windows
Step 6: Get a Floor
Step 7: Build the Roof
Step 8: Add the Shelves and Fans.
Step 9: Caulk and Paint
Step 10: Update: Spring 2009
This year I was able to obtain a large picture window and decided to install a windowed roof this spring. It will allow much more light in and therefore heat. I used the same deck screws to affix the windows to the roof frame I already had built. For the roof vents, I took two windows and screwed them together. I found old door hinges and used a piece of PVC as a brace. I added a screw holding it to the frame as a cotter pin. Lastly, In case a huge gust of wind came along and tried to yank open the windows, I nailed a small chain to the frame and window to prevent the window slamming backwards onto the rest of the roof.
I also modified the south facing bench. It connects to the frame on one end and still uses cinder blocks on the other. This will hopefully allow me to utilize the space inside better. It’s filling quickly!
Now that the roof will allow so much light through, cooling will be a greater issue this summer. I may place some of the old panels back up in July/August to reflect some of that light. I also have obtained some reflecting fabric.
Lastly, I think in the future, I will completely rebuild the roof, using the windows for a gable type structure. It will force me to use some sort of poly material to cover up the gable ends. The current pitch of the roof is not enough to slope water off the windows completely.
Step 11: Edit: Fan Window
Step 12: Spring 2010 Roof Vent Upgrades
Also pictured is a gutter claimed from the trash. The hinge side of the roof windows always leaked profusely. The gutter catches the water and stores it in a bucket for easy watering.
Step 13: Spring 2010 Shading
Step 14: Winter 2012
Here is the greenhouse in a mild winter. I overwinter many potted perennials inside. To insulate the roof, I stretch a sheet of poly across the top to keep out the drafts. Last October, 2011, I repainted both the inside and out. All the wood is doing well. I hope that, with care, the greenhouse will last over 10 years. It has changed the way I garden, making my back yard much more productive.