DIY Small-Space Greenhouse Using Salvaged Windows

Materials & Tools

Lumber

• (8) Pressure-treated 2x4x8 
• (10) Pressure-treat 1x6x6 Fence Boards

Windows

• Salvaged windows (similar sizes will make construction much easier)

Fasteners

• 2½” exterior wood screws
• Brad nails 2.5 inch
• Door hinges 1.5 inch
• Vintage latch
• Decorative door knob
• (6) 1.5 inch L Brackets 

Paint & Finishing

• Pressure Treat Wood Preservative
• Exterior Stain or Paint (optional)
• Masking Liquid H2O (optional for painting on windows)
• Window Glaze (as needed)

Tools

• Drill
• Circular Saw (or plunge saw is optional) 
• Miter Saw 
• Jigsaw 

Gardening Supplies

• Miracle-Gro® Fruit & Veggie Shake ‘N Feed
• Miracle-Gro® All Purpose Shake ‘N Feed
• Miracle-Gro Potting Soil Mix for Indoor and Outdoor Container Plants
• Flowers, herbs, and vegetable plants

Step 1: Source Your Salvaged Windows

The windows are the heart of this project. Look for old wooden windows at salvage stores, online marketplaces, or local buy-and-sell groups.

Find windows that are relatively similar in size. They don’t have to match perfectly, but the closer they are, the easier the build will be.

Lay them all out on the ground first and experiment with different layouts until you find one that works. This step is a little like putting together a puzzle, but it’s worth taking your time before making any cuts.

I chose to make a cube shape with a slanting roof.

NOTE ABOUT WORKING WITH RECLAIMED WINDOWS:  

Before sanding, scraping, or stripping old paint, it’s always a good idea to do a lead paint test, especially on windows from homes built before the late 1970s. Lead test kits are inexpensive, easy to use, and can be purchased online or at most hardware stores.

If the test comes back positive, avoid dry sanding or scraping the paint, as this can release hazardous lead dust into the air. Instead, use a chemical paint stripper designed for lead-safe paint removal or wet scraping/wet sanding techniques to keep dust to a minimum. Be sure to wear appropriate personal protective equipment (gloves, eye protection, and a properly fitted respirator) and clean up thoroughly using wet wiping or a HEPA vacuum.

Step 2: Restoring Old Windows

Salvaged windows usually need a little “TLC.”

Scrape away any loose or peeling paint using a paint scraper. If the glazing around the glass has deteriorated, remove the damaged material and apply fresh window glaze to reseal the glass.

If one of your windows needs to be resized to match the sizing of others (which is what I had to do), use a saw to trim the wooden frame only – never cut through the glass.

NOTE ABOUT WORKING WITH PRESSURE-TREATED: Once all pressure-treated lumber is cut, seal all cut ends with a PT wood preservative to help prevent moisture damage and rot.

Step 3: Greenhouse Base

The base raises the greenhouse off the ground, helping protect it from excess moisture, creating valuable storage underneath, and placing it at an optimal height to save your back while gardening!

My Cut List : 

• (4) 2×4 PT lumber at 28 inches (legs)
• (4) 2×4 PT lumber at 30½ inches (table frame depth)
• (8) 2×4 PT lumber at 32 inches (table frame width & Support Joists)

*Before adding screws, make sure to pre-drill all screw holes to avoid wood splitting.

Start with your table frames. Build two identical rectangles, making sure to orient the (2) 32” lumber to be front facing with (2) 30 1/2” lumber budded up, square, on the inside. Fasten two screws from the front on each end. 

Connect the two frames using the (4) 28” legs set at each inside corner, spacing the top rectangle (base top) and the bottom rectangle (shelf) approximately 13½ inches apart. Secure with wood screws.

Step 4: Add the Base Shelving

Spaced equally apart, Install two support joists across the inside of the top and bottom frame. These supports should fit tightly between the frame, so don’t be afraid to tap them into place with a mallet before fastening.

Cut the PT 1×6 fence boards to fit the width of your base. Install them horizontally across both the top surface and the lower storage shelf. Leave a slight overhang on each end of the top boards to create a finished look. 

On the bottom shelf, use a jigsaw to notch the boards that meet the corner legs so they slip neatly around the posts, then secure everything with a brad nailer.

Step 5: Assemble The Greenhouse

Once the base is complete, it’s time to build the greenhouse itself!

Some reclaimed windows may need to be trimmed to help square the edges, or simply to make them smaller, while others will need to be framed using PT lumber to make it bigger. 

To determine my PT framing, I measured the width of the windows and cut down 2x4x8 PT lumber to the same width and size. This can be done using a tablesaw, circular saw or plunge saw. I like to add pressure-treated framing to help square the house and give the windows additional structure when securing together with wood screws. 

Using the same cut PT framing, I added a front crossbar at the top for additional support. Secure your windows into the desired framing shape with wood screws. 

*OPTIONAL: If you pick a similar shape greenhouse,  the roof will create triangular gaps near the gables. Feel free to leave this open (air flow is good!), or cut matching triangular pieces from pressure-treated lumber to close everything in. 

Install the door using two door hinges. At this point, your greenhouse should be fully standing on its own!

Step 6: Finish and Paint the Greenhouse

Sand any visible lumber markings from the pressure-treated wood and apply wood preservative over any areas that are needed.

If your pressure-treated lumber is dry enough to paint, you can apply a light exterior stain or paint to enhance the look of your greenhouse. 

PAINTING PRESSURE TREATED WOOD NOTE: If working with fresh pressure treated lumber, you may not be able to paint until it’s had time to thoroughly dry. If you paint PT while wet, the moisture from the wood will eventually surface, causing your paint to bubble and crack. 

PAINTING WINDOWS? Painting windows is tricky but here’s a cool DIY tip! Use a Masking Liquid first before painting. A masking liquid can be added right onto the glass and your frames. Once dry, it creates a protective barrier on the window glass allowing you to paint right onto the glass for easy painting. Once your paint is dry, simply score around the inner window pane and peel it away for perfectly clean glass with no paint left behind. 

For my door, I chose a bold red exterior paint to give the greenhouse a cheerful focal point, then finished it off with a vintage brass latch and a whimsical floral knob. Those little details are what really give this project its whimsical garden charm.

Step 7: Interior Shelves

To maximize growing space, I added shelving inside the greenhouse.

The shelving supports were built from 2×4 pressure-treated lumber that was cut into 1½” x 1½” pieces. These supports were secured into the inside corner framing of the greenhouse at the desired heights. 

The shelves, made from leftover fence boards, had one end cut at 45 degrees for easy access in the front, and were secured to the top of each cross support. 

I installed two shelves on the left side and a single shelf on the right, creating plenty of room for seedlings while still leaving space for taller plants in the middle.

Once the greenhouse was completed, I secured it to its base with 1.5-inch L-brackets.

Step 8: Fill It With Plants

Now for the best part! Fill your greenhouse with herbs, flowers, seedlings, or vegetables depending on the season.

I planted a mix of whimsical flowers, kitchen herbs, and vegetable plants to create a greenhouse that’s just as beautiful as it is functional.

I also keep Miracle-Gro® Fruit & Veggie Shake ‘N Feed and Miracle-Gro® All Purpose Shake ‘N Feed stocked on the lower shelf, so they’re always within reach whenever my plants need a nutrient boost throughout the growing season.

Final Thoughts

This project is proof that you don’t need a massive backyard to enjoy the benefits of a greenhouse.

With a handful of salvaged windows, some basic framing, and a little creativity, you can build a beautiful greenhouse that fits almost any outdoor space. 

Every collection of salvaged windows will be different, which means no two greenhouses will ever look exactly alike – and that’s what makes this project so special! Want to see more of these kinds of projects? Follow me on Instagram, Facebook, Pinterest.

Happy gardening, friends!

#happycreating!