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DIY Build Your Own Greenhouse For Under $150 | Tutorial

DIY Greenhouse for under $150!

Almost 2 years ago myself and hubby built a little greenhouse from old planter boxes,
strapping and left over poly vapor barrier.

I'm not a big fan of plastic but reusing what you have is better than sending it to the landfill.
We were hoping it would last through one winter but it has not only lasted through the winter, it withstood hurricane Igor with only minor damage to a roof vent.

Here is the greenhouse today, We used some hooks and tied it down with straps for the storm:

There was a tiny bit of damage when one of the roof vents opened in the wind, the frame cracked.

Here are the instructions from hubby on how we built it:

Step1: The Beginning

Building a greenhouse. 
We had looked at purchasing one, however the good ones are really expensive and the cheaper ones (while not much cheaper) have quality issues.

We already had several raised garden beds from last year as a base so we decided on building a poly sheathed greenhouse to cover the raised beds. The two in the picture are different widths, however they are 8’ long 2×10 spruce held together with lag bolts in the corners.

The concrete block is off center because of the different widths of the beds. It represents where the door will actually be located.

The larger bed towards the top of the pic will be outside
of the structure and will be used for herbs.

After we had the beds in place I ripped several 2×4x8 construction grade spruce in ½ to give me 2×2s to use for framing. Here I am assembling one of the side walls. The lower 8 inches (to the right in the pic below the piece of strapping) will go inside the raised beds and bolt to the sides for stability.

That’s it for now.

Step 2: The Middle

Tonight I built the back wall for the greenhouse. When measuring for the top plate I had to subtract the measurements for the two outside walls. I didn’t realize this until I had it all put together…At least I never cut it to short in the beginning.

Here I am holding up the new back wall with the two side walls in the background. Oh…I still have to install the braces.

FYI I am using screws for all of the construction. I hate nails.

Step 3: Going Up

Yesterday afternoon I finished off the front wall of the greenhouse and we installed the walls into the raised beds. The bottom 8” of the walls (that would go into the box and in the soil, we wrapped the wood in plastic so as to avoid rot. Colorful Canary dug the trenches. The fit was a little tight, which I expected. I was expecting things to be a little out of square as I used ripped 2×4s, but surprisingly it was not too bad. Enjoy the pics.

Step 4: Topping it off

Got back at the greenhouse yesterday evening. There were a couple of details on the structure that needed finishing. On the rear, down near the ground, between the two boxes I had to add a bracket so that the poly could attach. No biggie.

I had to add a small “extension” to the box in front to cover up the leg of door frame. I needed this as the boxes were not the same width and in order to keep the symmetry one of the legs had to go outside of the planter box. I managed to find some weathered wood to help the extension blend in. Pocket screws front and back. I finished it off with a small brace in the back.

I was a couple of 2×4s short so it was off the Home Depot. While there I picked up a mess of black gate hardware for the door. I ripped the 2×4, took some final measurements and started on the roof of the greenhouse.

It is not actually that heavy. I still have to put in braces and frame out for two roof vents.
Then build the vents.

Step 5: Progress

Over the last couple of days we have made some progress on the greenhouse. I finished framing the roof, made the vents, trucked some nice crushed stone into the “walkway” and coated all the wood in a mixture of sunflower oil, activated charcoal and iron oxide (from LV). Colorful Canary helped (did most) with the staining.

Next is to apply the plastic to the top and bottom, connect the two and make the door.

I was thinking about using lag bolts to keep the roof and sides together, but tonight I decided that I will use ¼ bolts, washers and nuts. This will allow me to take it apart more easily if I need to replace a section.

Step 6: Installing Poly

I started by drilling holes through the top plate of the walls.

When we install the roof I will redrill the holes through the roof frame so that I can bolt it all together.

We unrolled the 15 mil polyethylene vapor barrier around the greenhouse and cut it. We then unfolded it and started attaching. Here I am marking it with a Sharpie so that we will have 6’ overlap on the top plate.

Going around the sides. This is definitely a 2 person job.
Colorful Canary has taken a break to take a pic. I’m marking again.

Here is an inside pic.

That 6” that I marked, here I am folding it over the top plate and stapling to the inside.

More stapling. That is a spring clamp to my right temporarily holding up the poly.

Here it is almost all installed.

Another view from the garage deck. Colorful Canary is going to cut off the excess at the bottom.

Not really sure what I am doing in this one. Oh . . . I remember. I’m installing 3/8 x ¾ strips of pine sandwiching the poly between it and the frame. There was no way the 3/8 staples will hold the plastic so I ripped some D4S pine. I’m using 1 ¼ brads shot on an angle.

This is a better shot.

Me with a goofy smile and Colorful Canary taking a pic from the second floor of the house.

Pretty much done here. Some additional trim work to do.

Step 7: Roof Finishing

I started this evening’s work right after supper attaching the hinges to the vents. I picked up a couple of pair of cabinet door hinges for $2 a set. I had to do a little chisel work so that they would fit properly.

Once again here is the finished roof frame off the floor for easy access. I later regret having it off the floor or at least not having it clamped to the stands.

Here I am attaching the plastic to the front.

Using the clamps again to hold the plastic prior to staples.

Back of the roof completed.

View from underneath showing the front and back

When unfolded the poly was 10ft long. It was plenty long to cover front to back.

A couple of pics of the finished product without the strips.

Colorful Canary's hand cutting out the vent hole.

Me attaching the vent. This one was a little tight so I had to do some trimming with a hand plane.

Vent installed

Finished with the strips and on the floor. Remember I mentioned about being up on stands and not clamped . . . well when I was up on a step ladder installing one strip I leaned a little to hard on the roof and pushed it off the stands. One stand went through the plastic. ARGGGGGGGGG. In these pics we had replaced it. Can you see the fix?

Step 8: Roof goes up

This is what we did tonight.
It was a little windy and drizzly tonight, however we were determined to get the roof on. I started by attaching two blocks on each side of the roof on the inside. Once the roof is up on the frame these blocks would guide the roof back along the sides. The theory is that it would prevent the roof from sliding off to either side. Theory did actually work in this case.

Bolting the roof on

Roof from the inside

Various pictures of the roof attached.
Take a look at how Colorful Canary prettied up the ground in front.

Step 9: Roof Details

Colorful Canary posted the following on the construction of the roof . . .

Hubby ripped 2×4’s in half so if you buy pre-cut 2×2’s that should work. Being that the roof is on a 12/12 pitch most everything is cut straight or on a 45 degree angle. Just think of it as making the diagonal half of a square box. Whatever you choose to be the width of your structure, you simply calculate half of the width to give you the height of the roof to the ridgepole. For example, an 8’ wide structure with a 12/12 roof – the roof would be an additional 4’ high to the center (highest point). Then you simply calculate the hypotenuse of 4’ x 4’ and this will give you the needed length for the trusses for 4’ square (48”) this would be a little over 67”. so you make your triangle with an 8’ base, a 4’ center post and two 67” trusses attached to a ridge which is the length of your shed.

From this pic you can see what it actually looks like. The width (red) is 8 feet and the height (green) is 4 feet. Remember that the height is from the bottom of frame to the top of the ridgepole. This will give you a steep 12\12 slope. If you wanted to decrease the slope . . . shorten the height. With our roof I did not do the calculation . . . I placed piece of 2×2 against the end of the ridgepole (top blue arrow) and marked it directly on the rafter. This was then my template.

This is where the rafters meet the ridgepole

Rafters meeting the base

Braces going through the center. Notice the pocket screws.

Another rafter view
Roof vent \ window framing

Step 10: The Door

Well today the weather forecast said it was going to be 1C with lots of RDF (rain, drizzle and fog). And that is what we got. Did this inclement weather deter me from building the door . . . heck no. Did it deter me from installing it . . . heck yes. I spent about two hours building the door. Hope you enjoy the pics.

We had a canning rack in the upstairs of the garage and Colorful Canary thought it would be a good idea to put it in the greenhouse as someplace to place her seedlings. Two screws held it in place.

Cutting the boards for the door.

Ripping some boards to the proper width.

Loose fit of the door just waiting for pocket screws.

A couple of pictures of making pocket holes. The system that I am using here is my older pocket hole jig. For my B-day Colorful Canary got me the Kreg Master System. I have not started using that one yet.

Using clamps keeps the board together.

Now you may be asking what type of hardware are you going to use on the door? I knew that Colorful Canary wanted black hardware so when I was in Home Depot I picked up just about every piece of hardware that was there to give her a good selection

This is what she selected. The remainder will be returned.

Here it is installed. Oh . . . that red smear . . . that’s DNA. Every wood project that involves sharp tools required a small amount of DNA to be added to the project.

I made a slight modification to the latch. The handle was pulling through so I drilled a small hole in the handle and installed a brad nail.

Finally here is the completed door. Note that the hinges are also installed. The second pick you can see the bracing. All those little black dots are drywall screws.

Finally here is the detailed drawing that I used for the construction. For those not familiar with construction drawings or lingo you may find it a little confusing.

I will hopefully install it tomorrow.

Part 11: Doh and Dough

Last night I was reading some Sherlock Holmes after Colorful Canary and I watched a movie and something struck me. No it wasn’t her wanting me to turn out the light . . . it was the fact that the latch for the door was an in-swing and the hinges were an out-swing. Doh !!

I definitely needed Sherlock and Dr Watson to help me figure this one out.

After work this evening I started by attaching a couple of screws to test fit the door.

The next thee pics you may remember from my last installment.
You will notice that the latch will only work when the door swings inwards.

I had to take apart a section of the door in order to make an in-swing latch into an out-swing. You can see the extra board that I am placing over the frame on the inside to give it more depth.
No extra DNA tonight when using the chisels to cut the hole.

Here I am walking through my redesign stages for the latch.
I am testing the swing and length of the black bar.

This is the latch modified and in place.

Here is a video of how the modified latch works.

After it’s all said and done you may be asking “How much did that really cool looking greenhouse cost.” Thanks for asking and here are the approximate costs in CDN$
Lumber (spruce) Raised Beds - $20 (estimate -had them from last year)
Framing - $40 (2x4s ripped in half)
Strapping - $15 (bracing and door)
Hardware Lag Bolts - $5 (to hold the beds together)
Screws - $10 (2 ½ and 3 ½) Bolts - $3 (mating roof to walls)
Hatch hinges - $4 Door hardware - $10 (hinges and latch)
Plastic - $30 ((estimate -had it from home construction, about 1/3 of the roll remaining)
Staples - $5
Total $142 + time (2 weekends and 2 weeks of evenings)

Part 12: Final Product
And the final product. I have a couple of more small items to finish up . . . but overall it is completed

Scratched this off my DHTDL a couple of days ago.

Greener Pics:

The last pics I posted of the greenhouse the surroundings were rather bleak and brown.
Here are some updated photos taken Aug 1, 2009.

The Harvest

Last year (the first summer) We yielded 89 tomatoes, 6 peppers and a few squash. This year (2010) 230 grape & cherry tomatoes and 3 musk melons.

The Update
2019 and still holding strong 11 years later.
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