Carport-Frame Greenhouse Design

Quite a handsome little greenhouse, don't you think!

One of the guiding principles of the Sharing Gardens is to Re-use and Re-purpose as many materials as we can - to keep them out of burn-piles, and the dump. This carport greenhouse was made with 100% salvaged and donated materials (we didn't spend a penny!) Such a beautiful demonstration of what the Sharing Gardens are all about!

Here is a greenhouse we made using a metal carport frame, pressure-treated lumber and plywood. (Finished size - 10' x 20') Windows and doors were all donated. You'll want to be sure to have windows at both ends that can open and close so your greenhouse doesn't overheat. We've assembled it entirely with screws, which makes it possible to disassemble and move. Someone donated the aluminum track (Installing Spring Wire Lock Channel for Greenhouse Plastic) to attach the plastic but it can be expensive to buy it new. On other greenhouses we've built, we've used long strips of lathe to screw down the plastic.

Finished carport greenhouse - side view.

Note unpainted vent-door at peak. Greenhouse is cooled by convection; cool air comes in lower windows at south end and exits through upper vent and door. Window on left is also operable.

One end from inside. Plywood construction means you can hang shelves/tool rack.

One end is all glass (two sliding windows) and greenhouse plastic for maximum light.

Here are some close-ups for construction details:

Begin by setting up frame on level ground with the ends facing east and west; this gives you maximum sunlight for your plants throughout the day..

Use 2 x 4's to frame side-walls. Upright metal posts are on bricks or blocks of wood to keep structure level and prevent it from sinking into the ground. Any wood that touches the ground should be pressure-treated.

Splicing 2 x 4's. The inner board makes a nice support for a shelf or tables.

The next step is to install a pressure-treated 6 x 6 across the bottom of the end walls. In our case, we spliced two shorter pieces together with a full-length 2 x 6. Keep making the structure level and square. This will make the rest of your framing much easier.

We use metal plumber's tape to secure sides to poles. Note painted cedar 1 x 4 "sill" and metal track (Video on spring wire/wiggle wire installation) to attach plastic.

Detail of inner walls. If you don't have corrugated fiber-glass, you can simply use more greenhouse plastic, or plywood. A clear or opaque material will let in maximum light.

Detail - outer corner. Note - we used 2 - 8" lag bolts to fasten lower corner to 6 x 6.

Detail - inner corner.

End wall, ready for framing and windows.

Next stage is to frame the end-walls:

This shows one of many possible variations for framing end wall. You need framing for windows or vents and to be able to attach plastic all the way around.

End wall framed for door and vent above door.

Framing details: 

Upper corner detail. 2 x 4's cut with a reciprocating saw (Sawzall).

More end wall:

Aluminum-framed, sliding windows for ventilation.

End wall framing.

Other end wall (still needs vent above door). Making part of the end wall out of plywood is great for hanging tools/shelving but it also cuts down on light coming into the greenhouse.

Attaching plastic:

This is what the Spring Lock track looks like. The plastic is laid in the track and locked into place with the "wiggle wire". (Plastic not shown...it goes between the wiggle wire and the track)

Detail of corner showing plastic wrapped around and attached on end-wall, and along 1 x 4 sill on side with spring lock/wiggle-wire.

Plastic attached along sill. The nice thing about this method is that you can go back and stretch plastic to be taut and even (which we did after this picture was taken).

Skid-free ramp.

Greenhouse in use:

Jen and Doreen transplanting peppers.

Austin, getting a transplanting lesson from Llyn.

  Latest use of this structure:

A few years ago, this greenhouse became overrun with the highly invasive bindweed/morning glory making it very challenging to use as a grow-sight. As the original plastic covering was ready for replacement, we decided to convert it to a storage building. We found this plastic cover for relatively inexpensive. It comes in rolls and is used to wrap silage (cattle-feed). White on one side, black on the other.

Inside our storage shed...

If you have questions or suggestions for improvements, please comment below.

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