Green House Build

The final dimensions of the greenhouse on the outside is 8×12. The inside measures 7’4″x11’4″. Two storm doors, four shelves, two fans, outlets for lights and heat mats, and a vent in the roof. This gave us enough space for 3 heat mats, 3 lights, and 12 flats per shelf. So, 12 heat mats, 12 lights and 48 seed flats. There will be a shorter shelf added to the top to hold a bit of this and that!

Gathering materials

Click here for A video tour of the greenhouse

Materials List:

Lumber: *keep in mind if you pick up utility grade lumber, that is not the typical dimensions you can save money, for this build everything was 6 ft material.

  • 3 @ 16ft long treated 4×6 for ground contact to build the frame.
  • 24 @ 2x4ft & 16 @ 4×4 tight knot cedar for framing walls and rafters
  • 4 @ 4x4x8ft standard and better Douglas fir
  • 1 @ 2x6x12ft Douglas Fir used for ridge board

Tin: re-purposed found in the loft of the barn, left over from the barn build 36 years ago.

  • 3 @ 2x14ft 29 gauge galvanized metal roofing

Double wall Polycarbonate for side walls:

  • 9 @ 2×8 ft from Home Depot, it was 40% the cost if we had purchased it at the specialty green house supply store.

Single wall polycarbonate for roof:

  • 6 @ 2x12ft
  • 12 @6ft Ribbon Board

Fans: Bathroom wall fan from Hardware Sales. 50 cfm. Currently in process, going to experiment with one for now. Might do two giving us 100 cfm, estimating the building volume at 900 cuft, making it so we can exchange the air every 9 minutes. **updates to come**

Storm Doors: $140 each at Home Depot. We opted for one at each end due to the placement of the greenhouse – it makes it easier to go back and forth as well as the benefit of airflow. This made it so I do not get a work bench, but he tells me he will make a drop down work bench.


  • Structural assembly 5 1/2 inch architectural screws exterior grade

Insulation: placed around the tin for warmth, put in place & spray foam applied

  • 2 @ 4x8ftx1 inch Owens Corning pink board

Shelving: Trex decking – Not necessary to permanently install for ease of drainage and removal when cleaning. We had a bunch of scrap left over, so we just ran with it. If we did it over again, we might use cedar because it’s cheaper, or wire – however, the trex keeps it nice and warm when starting seedlings and it won’t rot. The downside is that it is super heavy and kind of pricey!!

  • 12 @ 1x6x16ft cut to fit the area

Electrical: With the need to plug in heat mats & grow lights there was a need for many outlets. We also needed overhead lights, and power for the fans. **updates to come**


  • 4 @ 1 inch Z strip metal drip edge

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