On the Farm: Building a DIY Greenhouse (For less than you think)

So, I have been thinking about building a greenhouse since I started work on the farm and the Christmas Break gave me the perfect opportunity to build that idea out.  The only problem was …ahem..money.  Professional greenhouses can span acres  and are so environmentally controlled that their costs can skyrocket into the millions.  Even hobby greenhouse kits, which emulate the pros, begin around a thousand dollars.

So I found myself in a bind, because I need to grow tomatoes, cucumbers, and peppers for the kids in the cafeteria but as of December was relegated to starting seeds on a small bench inside a dark shed.

This was fine until the plants started growing…taller…taller.. and getting so leggy that they fell over and died. (I know the light should be closer…in retrospect.)  The temps were varying wildly and I really couldn’t grow that many seeds.  So, I started researching.

Websites, videos, blogs, and finally I happened upon a picture and explanation of a DIY Greenhouse at the blog, FromThisDirtForward.  The only problem.  No instructions.  So I studied the pictures and started scribbling away trying to see if I could make it work.  After a day or so, I decided it would be feasible and set out to build it.

Part 1:  The Base

Materials:

6-4″x4″x8 Treated wood posts

2-15/32″x4’x8′ Plywood Sheathing (retrospect: go with a thicker plywood)

1lb of 3″ galvanized decking nails (retrospect: decking screws. period.)

I scrounged around and found 6 wood posts and nailed the sheathing straight to them at 2′ intervals.  This will decrease bowing because of weight and keep the wood lasting longer.  I used treated wood because these were old posts that, if they leach, had leached years ago and were fine to use in the garden.

(Learning note:  Level out the base *before* doing anything else.  If you don’t it is painstaking to fix it later.)

Once these are done the next step is to build the frames.  One by one.

Step 2: The Walls

22-2″x4″x8′ Treated Framing Lumber

3lbs of 3.5″ Exterior Decking Screws

Each wall was built separately and screwed and nailed down to the base.  I chose to use 8′ boards so I wouldn’t have to cut many boards and could simply screw them together and frame them up.  It takes 5 boards per wall except the front which takes 7 because I framed out a door.  I did have to cut the vertical boards to a 6′ height so the last two feet will incorporate the roof.  So each wall composed of 2-6′ vertical boards and 3-8′ boards equally spaced along the vertical boards.

(Learning note: When you frame all boards to 8′ long, consider all aspects including the adjoining walls and their 4″ wide board face which adds 8″ to two sides of your structure. I adjusted the base, see image below, or you could cut two sides 8″ and achieve the same results.)

Once framed, you might notice it is a bit wobbly.  You’ll hear it creak and perhaps sway a bit.  Don’t worry, it will strengthen up alot when the roof and the side paneling are put on.

Step 3: The Roof

2-2″x4″x2′ boards

1-2″x4″x8′ board (Cut down to 7’9″ to account for the 2″x4″ vertical boards)

9-2″x4″x(roughly 51″)(to make the rafters) (1 board is a template)

1lb of 2″ decking screws

When making a roof you can easily come up with the dimensions using the Pythagorean Theorem, A squared + B squared= C squared.  Retrospect:  The more difficult part is cutting the perfect angle without a protractor or an automatic angle cutting saw.  I would suggest either or both to save time.  After a few tries, I succeeded in creating a template that I reproduced and made quick work of the roof.

(Learning Note:  Have another person helping is always a good thing.  I pulled a muscle or two trying to hold an 8′ board in the air with one hand and screw it in with the other.)

Also, you might notice there are floorboards in this shot but not the one above.  Which brings us to our next step…

Step 4: The Floor

I wasn’t happy with the way things were feeling when I walked around so I found some scrap lumber and started screwing them down to the base.  This was a good idea as it covered up the middle gap and strengthened the base alot.  I used 1″x6″x8′ boards that I cut into smaller pieces and screwed down.  You want an alternating pattern so one board gets too much stress. You could use pallet wood or anything else you find.  Just make sure you have enough to finish before you start.

Step 5: The Siding

2-4’X8′ exterior panels (ripped in half to cover a 2′ section of the structure all the way around)

This is where the strength comes in to play.  I screwed these in and stepped back and noticed I didn’t hear anything.  No squeaking or swaying.  It was solid.  I ripped these in half and it fit perfectly all the way around.  Even have enough to cover the door in the middle.  (Make sure cuts near the door are smooth so you don’t have a door that “catches” every time it closes.)

Step 6:  The Siding

For siding, I used 6 mil plastic sheeting you can pick up in any hardware store.  6 mil is the thickest and longest lasting and it gets really windy because of our proximity to the gulf so I didn’t want the plastic to shear off in a few weeks.  I also decided to double up and connect it to the structure twice.  The first was using a square roofing nail directly to the frame.

The second was to take furring strips (1″x2″x8′)  and overlay them on top of the frame and screw them down.

This secured them well. There is one note however.  When screwing down and putting force against the wood and screw.  Be sure to be straight on, because if you are angled you can slip and punch straight through the plastic.

Then you have to take a piece of scrap plastic and super glue it to the torn area.  It works well but isn’t the prettiest.  So be careful.

Step 7:  The Shelves

So slatted shelves will allow for drainage and add a bit of class to the greenhouse.  This takes a 2″x4″x8′ board that creates a 2′ deep shelve and is slatted using extra furring strips.  (Spacings are 1″ apart)  This is repeated on the other side of the greenhouse.  The second shelf is 16″ deep and will use the same slatted spacing and pattern.

So that is where we are at now with the greenhouse.  Mostly done, but with tweaks needed.

Part 2 will be up soon with more updates.

Back to the Farm,

Farmer Tuley

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