A backyard greenhouse for around $350!

One of the challenges of starting a business from scratch is keeping costs down when we don’t have any revenue to pay for our supplies and infrastructure. Kaila and Jason took on the challenge with gusto and designed a reasonably-priced backyard hoop house where a lot of our plants are going to live this summer before they go home with you all!

This is a long post, meant for those who may be interested in building their own structure, so we won’t be offended if you don’t stick around to the end! The executive summary for the TL;DR crowd is:

  • build a wood frame for the base and the door frame
  • use poly piping to create a reinforced hoop structure, attached to the frame using rigid straps and to the reinforcements using zip ties
  • cover the structure lengthwise with vapour barrier using staples and tape to secure
  • make clamps with your extra tubing to attach the plastic to the ends of the structure (stapled and taped at the bottom)
  • use adhesive zipper for a very simple door

Our goal was to create a temporary greenhouse structure that worked within our space on a tight budget. We settled on a size of 8’X20’ (160 sq/ft) with a max height of approximately 6’6”.   Many iterations of this structure were involved in the planning phases. We chose this hybrid design after watching MANY YouTube videos (links of few faves here here and here).  Most of the supplies were ordered online from Home Depot. (Our materials list is long and detailed, but please email us if you’d like a copy! We are more than happy to share.) I (Kaila) will describe the basics of how we went about this in two afternoons with two people, who have basic carpentry skills combined with a can-do attitude – which means you definitely are qualified to try this too!!

AFTERNOON 1

Create a rectangular base using mending plates and securing the corners square using your desired dimensions. Ours was 20’x 10’ mended, and 8’ on the ends.  Pre-drill all holes and secure with screws.

Measure out and attach rigid straps for the tubing to slide into on the inside of your frame closer to the top of the material. We planned for 8 hoops. We doubled up some of the rigid straps nears the edges but this many not have been necessary. If you double up, you will need more materials than we used.

Cut poly pipe tubing to length. We used a length of 17’, marking the centre and 24” in either direction for ease of attaching strapping later. (As a little cheat, mark your long side of the greenhouse with your necessary measurements (17’, 10’6”, 8’6”, 6’6”) and use as a giant ruler to cut all 8 pieces quickly and consistently.)

Slide tubing into rigid straps and secure with a screw (2.5”) affixed with a wide washer or flat head screw.

Cut 3 pieces of tubing the full length of the greenhouse and mark your hoop with increments. These will be your cross supports. 

Zip-tie the cross supports at the centre and 24” markings on your hoops. Use two zip ties in an X pattern, making sure the smooth parts are where the plastic will attach along the top to avoid abrasion points. We recommend 12”-14” ties here, anything less than a foot will be too short.

Measure the height of the top of the hoop at the back (non-door side) of the structure and cut a 2×4” to the height. Use a hole saw to create a groove for the tubing to fit into along the ridgeline. Secure the board upright at a 90 degree angle to the base using 3” wood screws. We used the cutoffs to create lateral supports. Secure the tubing to the upright with a long screw and a washer. The structure got MUCH more secure at this point!

Make a door frame with 2×4”. We used a 32” opening. Cut the groove for the tubing and take a jig saw and round out the corners along your hoop structure shape. Secure the tubing to the frame with screws and washers.

This was enough for one day! We took a break to wait for warmer weather…

AFTERNOON 2

Lots of patience and imagination was required on Day 2!

Lay out the vapour barrier and cut two sheets 6” longer than the length of the greenhouse. (We used a roll of 708″x102″. If you are using double-wide vapour barrier, you will only need one sheet, and will not need to do the mending described below.)

Mend the two sheets carefully together on the long edge with a strip of gorilla tape, using care not to have any bubbles or creases in the tape and that the plastic is evenly secured together. Affix a 12” piece crosswise on either edge for added support. Add another strip of tape on either side of the first with a 1/3 overlap. Flip the entire covering over and repeat the tape mending on reverse side.

I lined up the sheet with the length of the greenhouse at the base and proceeded to staple the sheet flush every 6” or so with the top of the 2×4” base on the outer edge. Tap any staples that didn’t get flush with a hammer . Following the staples along the long edge, I affixed a long strip of tuck tape over the stapled area and onto the wood to seal the staples and add stability.

I pulled the sheet over the body of the structure to the other long side (leaving the ends open), pulled it taught but not overly tight so there was still plenty of movement in the poly. Repeat the staple and tape process on this side.

This is where your creativity and patience will pay off. Take the plastic and wind a good fit around the end hoops securing temporarily with strip of tuck tape. Once the main body sheet has both ends secured to the end hoops, its time to cut the end pieces.

The ends were cut at 8’6″ off the roll. Line up your plastic sheet at the base with equal part overlap on either end. In my case it was about 3”. Repeat the bottom staple tape process.

At this point you want to make your tube clamps to secure the ends in place. I used about 50. To make these, cut 4-6” sections of leftover tubing, then take a ~½” length wise slice out of it. These will clamp onto the edges of the tubing and hold your plastic in place. Play around with a variety of lengths, having an assortment helps to fit around the various parts of the curve.

Pull the centre of the end plastic to the top centre of the hoop. There may be a helpful fold line in the plastic to get you lined up. Leave extra plastic at the inside (top) of the greenhouse with about 2” wrapping on the outside hoop, then pop on a clamp. Work your way fitting and clamping the plastic all the way down on one side, go back to the top/centre, then down the other side. You should have extra plastic on the inside of the greenhouse that you can cut away later.

Repeat on the door side, leaving extra length at the bottom this time to ensure you can get a good close on the door. On this side wall we added some extra staples along the outer edges of the door where the zippers would go. Use them sparingly, you can add more later once the zip is in and you are sure on the positioning.

Stick adhesive zippers along 2X4 door frame, leaving extra at the top and making sure the zipper is the right direction and goes right to the bottom. Open zippers and cut plastic to create door. Add a few staples to get a better fit. Add something to hold your door open when you need to go in and out or when its too hot, such as ties or Velcro.

There you have it! Once again, do not hesitate to ask us for the materials list or for clarification on any of these steps if you decide to build a similar structure of your own!

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