How To Build Your Own Greenhouse from Carport – Part 3

Note: This DIY Easy Carport Greenhouse Project post series is continued from Part 2 and Part 1, so go read them if you haven’t yet.

OK, then. All here? Good!

Let’s get to it!

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Step 9: Attach corner cushions.

Because the plastic will wrap over a wood edge, I padded them with pipe insulation to avoid tearing of the plastic.

Corner cushion detail

So I used my handy-dandy HF brad/staple nailer (pneumatic powah!) with narrow crown stapes to secure them to the corners. Those dimples you see in the inset are where the staples secure the insulation to the wood.

The insulation only has to stay in place until I get the plastic film on, I hope.

I ass-ume that the plastic will hold the insulation on, but you know what happens sometimes when you ass-ume things.

Also, I made sure to overlap the insulation at the ends so that water wouldn’t leak down between the insulation and wood.

Don’t want it rotting too fast, now!

I also had to be careful to not staple too deeply (turn down air pressure) otherwise the staple would go right through, and not help hold the insulation on.

The cheapie HF stapler performed pretty well, even after it got dusty it still didn’t jam or misfeed.

I have a friend (shocking, I know!) who has the same nailer and he said his works great too.

I think the trick to keeping these cheap nailers working right is making sure to oil them often, as in daily or at least every time you use it.

Anyway, I just wanted to NOT be fighting the insulation when I installed the plastic, which turned out to be hard enough!

Step 10: Install door.

Optional, but the greenhouse is harder to get in to without it.

The door just a rectangular-ish 2×4 frame with a diagonal brace to keep it from sagging. After installing it I noticed my lack of square and plumb while framing the door opening.


One corner of the door sticks out further than another by over an inch.


Greenhouse door

I’ll have to re-work the door frame to fit the opening, but it works for now. Did I mention my time is limited?

I used (Habitat for Humanity) Re-Store sourced door hinges, but have yet to installed a latch. I use a heavy bucket instead.

I did mention my time is limited? Yep, sure did. Just above there. Excuses, excuses!

Yeah, I know, I’ll get to it. I really do like crossing projects off the list. But it’s a very effective bucket…

Step 11: Apply film.

Hey, who’s that weird-looking guy in the overalls and tie-dye shirt on the ladder?

What a freak!

Oh wait, that’s me. Uhhh. Awkward…

No more pics from behind!

Greenhouse film installation in progress

Apply film.

So simple to say. Not so easy to do.

So if you’re playing along at home, here’s a helpful tip. Need to do some relationship counseling? Just try putting film on a greenhouse in a 15-20 mph wind.

Very relaxing and emotionally soothing.

And by relaxing I mean TOTALLY NOT RELAXING!

Stressful and hard on the emotions, I tell ya.

Why did I do this?

Because I’m an idiot, but you already knew that. Ha!

So the reason I tried installing a giant sail in the wind was this: every day I had time and energy to install the film, it was very windy.

So I waited, thinking surely it won’t be windy the next time.


Maniacal laughter, maniacal laughter!!!

And don’t call me Shirley.

This happened several times and finally I just decided it had to be done, otherwise I never would have tried to do this.

It really was an exercise in frustration.

But the show must go on!

I attached the film to the perimeter wood with 4-foot wood lath and the same pneumatic staples as I used with the corner cushions.

Sidenote: Another option used in commercial greenhouses that I looked into is called “wiggle wire” channel. It’s a C-shaped channel that holds the Z-shaped plastic-coated wire that “wiggles” back and forth in the channel.

This holds the plastic firmly without damaging it. It’s also very easy to reposition, remove, or tighten the plastic.

I chose not to do this because I priced it out and it was not cheap. It would have roughly doubled the cost of my (not so cheap?) greenhouse. In retrospect, I should have just bitten the bullet and gone with wiggle wire.

The ease of installation and ability to (re)tighten any portion of the film surely outweighs the one-time cost of a wiggle wire system. It is possible to go too cheap and be more costly in the end.

The lath method worked fairly well, considering I had to fight with the wind and work with the “helpful” children and spouse. And I mean that in the nicest possible way.

One consequence I noticed fairly soon, however, was that tightening or repositioning the film was very difficult.

So I should just do it perfect the first time. Is that a problem?


The greenhouse ended up with wrinkles in the plastic (looks sloppy and flaps in the wind, ugh!) that I cannot tighten without breaking the lath off, removing the staples, and attaching new lath while tightening the plastic with my third hand.

Zaphod Beeblebrox of Hitchhikers Guide to the Galaxy comes to mind.

When I replace the plastic, I will install the wiggle wire and channel. Much easier to remove or tighten the plastic that way. Until then I’ll just put up with it looking, let’s say, slightly less than professional.

Or amateur, yeah. Or sloppy. Ugh!

Step 12: Enjoy being done with the project. Mostly.

Maxin' and relaxin'

This I prefer with white wine.

Cost analysis – Show me the moneee!

Existing items

  • Carport frame – $0
  • Wood (scavenged) – $0
  • Screws (est.) – $1
  • Door hinges (est.) – $2

Purchased items

  • Plumbers tape – $10
  • Greenhouse film – 20′ x 38′ – $76 + $30 shipping = $106 total
  • Wood lath – $15
  • Pneumatic staples – $8
  • Total: $142

I already had most of the existing expensive items (sans film) on-hand, like the wood, but if I had to buy the wood it probably would have cost another $50-60. Previously, I bought wood screws in a $50, 25-pound box, because they’re much cheaper per pound that way. I think a 1 lb. box is $7.

Obviously the film was the single most expensive item, and the shipping was a large part of that. If I could have found it locally I would prefer to go that way.

If I would have chosen to do the wiggle wire, I would have cost me another $114 + shipping. It would have roughly doubled the cost of the greenhouse, but when considering the ease of adjusting the plastic, it would be totally worth it. So for about $300 I could have a solid greenhouse that would be easy to replace or adjust the plastic.

Final thoughts

Thumbs up!

All things considered, I think this project was worth the money and time cost to build it.

It’s amazing to experience the temperature and humidity difference between outside and inside the greenhouse.

It’s also a good example (lath instead of wiggle wire) of when trying to go “cheap” costs you either in time, money, or aggravation.

Third, having a secure (read:not cat infested) place to start plants is a big bonus. I’m expecting to be doing much more growing and seed-starting with this greenhouse.

I’ve already

  • Planted the south beds with cold crops like lettuce, kale, radish and peas
  • Started summer veggies in trays

I have ideas about having a small PC tree nursery, at least to be able to do my own grafting of fruit trees and bushes.

I may branch out and start selling plants in the future. We’ll see.

And again, I wish I would have gone with the wiggle wire channel rather than the lath method of attaching the film.

Don’t be cheap like me!

Next steps

I will make a workbench & shelves to

  • Have more growing space
  • Easily start nursery trays
  • Work on plants

I also may put quail and red wiggler worms in a stacked setup under the workbench.

I need to add bottom and top vents (hopefully automatic) to keep the greenhouse cool.

Since heat normally rises, putting in a low intake and high exhaust should help to cool passively without having to add electric fans or a swamp cooler.

And I may add beds similar to cold frames to the south side. These would allow better ventilation and extend the growing area.

I’m thinking about adding rollup sides to the greenhouse to aid in summer cooling.

I like the way Curtis Stone of Green City Acres in Kelowna, BC ( does rollup sides on his greenhouses.


I also REALLY want to add an aquaponics system.

‘Cause you can see some crazy fast growth in an AP system.

I’m considering sinking the tank into the ground and lining it with pond liner, which would save me valuable floor space, and I can put in beds and overhead trough systems that save even more.

I’ll be posting updates on these greenhouse improvements, as I go.

Wow, what a project! Glad it’s done-ish. There is for sure more to do, but it’s enclosed, and that’s the important part.


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OK, that’s all folks! Do you have any questions or comments about the greenhouse, the build, or gardening? Ask your question down below and let’s talk! You can also use the contact form, or email me at info at thepermaculture dot life.

Thanks from TPL

P.S. If you’re looking for a cost-effective quality greenhouse you don’t have to cobble together, there’s a solution.

Bootstrap Farmer has greenhouses that are the lowest price per square foot online, including shipping!

They also have lots of greenhouse and farming accessories. Check out their Greenhouse Kits.





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