Gardening 101 ~ Building a Greenhouse

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Hello! We are Merissa’s mother and father in-law, Paul and Mary, and it is an honor to be asked to have a guest post on her blog. She asked if we would write about the greenhouse we are building out of discarded patio doors. My husband and I like the idea of “re-purposing” (Finding another useful purpose for things that would otherwise end up in the landfill.) So when a friend of ours, who replaces doors and windows for his company, told us he had several glass patio doors that were going to be discarded, my husband came up with the wonderful idea of building a greenhouse. He has wanted to build a greenhouse for quite a while, but the cost has been inhibitive. Our first intent was to make a cold frame with one or two doors, but when we had access to 10 at once, we decided to go with the greenhouse. Paul designed the building frame to fit the doors, and to let in the most southern sunlight, so we can extend our growing season. It is 8′ x 12′ so there is plenty of room for tables and moving around.

As you can see from the pictures, he put four of the doors at a slant for the roof, and four at a slight slant for the south wall. The other 2 doors he put in the east and west walls. The north wall is solid. We insulated the north, east and west walls, and put on particle board. We plan to put in a fan, on a hinge, in the west wall, so it can be closed and insulated during the winter. We have a vent in the east wall for air circulation. We sided it with metal siding left over from our house roof. All the holes in the doors were caulked to keep out the moisture.

In the inside, along the north wall, we made planting trays out of plastic gutters, which we mounted on shelf brackets. I caulked the end caps on to hold the soil and water. We got the gutters at Menards for .99 after rebate, and the shelf brackets were free after rebate. The most expensive things were the end caps, which weren’t on sale. Paul has planted radishes, spinach and lettuce in them and the seedlings are growing well.

We really haven’t proved how well it will work yet, but the temperature is usually 20 or more degrees warmer in there, when the sun is shining. We hope to put cement patio blocks on the floor this fall to help retain the heat. We also hope to put in some dark painted barrels, filled with water,  to also help hold the heat for when the cooler days of fall and winter come.

We are looking forward to using it and see how well it works.

Thanks to Paul and Mary, my mother and father in law for this guest post.

The Gardening and Preserving Journal is here! If you are gardening or planning on doing any preserving this year, you NEED this wonderful sprial bound journal! Get your own copy here.


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  1. Thanks for the photo of how it went together. I am working on something similar with some discarded 5×6 ft windows.

    What is on the floor now? Regular cement/concrete?
    And will the patio blocks be a darker color?


    1. I thoroughly enjoyed reading this post, and am inspired to replicate the green house. Awesome and thank you for sharing.??

  2. Hi Marci, This is Mary. What we have on the floor right now is just used carpet to cover the dirt. Yes, we’ll put in the darker patio blocks, when we can afford them. Thanks.

  3. OMgosh I wish I had found this site before buying a greenhouse. (even though we love ours) I love the idea of the gutters though and plan a trip to our local HOME DEPOT tomorrow to set this idea into use.. thank you .. What fun it will when we can have fresh orangic veggies all year long.. FYI we are making a move to the coast and will live there full time.. the deer are everywhere so this green house is a blessing if you want to grow your own..I cant wait to show my brother this idea ….

  4. Loved your greenhouse from recycled patio doors. Could you plz give more pics of patio doors connecting to the framework. Do you mind giving a floor plan yo me? To my gmail address….So my hubby could see it. He has never built a project greenhouse before..from scratch…Were on a tight budget think this would be a lovely savings idea….Thankyou for sharing …what a wonderful idea!!!..Love the gutters on the walls…

  5. Get the book The Compost powered Water Hearer by Galen Brown and heat your greenhouse as outlined there or go online and check out the way Russell Finch figured out how to both heat and cool his greenhouse. His is huge and runs all year as it is able to stay cool in summers. It costs about a buck to run per day! Feeds almost 200 people also. Yours might be able to be converted to his design. Greenhouse in the snow is on YouTube. I think Mr. Brown is as well.