$500 Greenhouse: How To Build A Hoop House

greenhouse hoop house how to build a hoop house

What is a hoop house?

A hoop house (also called a polytunnel or hoop greenhouse) is a greenhouse with a plastic roof wrapped over a flexible structure of hoops. The interior heats up because incoming solar radiation from the sun warms plants, soil, and other things inside the building faster than heat can escape the structure. The large hoops or bows can be made of metal, plastic pipe, or wood. The heavy greenhouse plastic “skin” is then stretched tight over the hoops and fastened to baseboards with strips of wood, metal, wire or even used irrigation tape and staples.

greenhouse hoop house how to build a hoop house

Hoop houses are affordable, fast and cheap to build, and can extend a growing season by at least a month or more on each end. Click here for an extensive article on hoop houses if you’d like to read more.

Here’s a 60 second video on small hoop house construction for under $50:

WHY BUILD HOOP HOUSES?

The goal with hoop houses is to add a couple months to any short growing season. In some places this will allow people to quickly begin food production while we are waiting for other larger Phase II food production structures to be built. We will use this page to open source share our evaluation of hoop houses as a growing option, how they work in our specific location, productivity and maintenance requirements, and related topics like manual venting needs, effects of weather, wildlife, etc.

Our initial objective is to construct eighteen 11’ wide x 90’ long x 8’ high hoop houses for:

  • Seedling starts of warm-season crops (tomatoes, peppers, eggplant, etc.)
  • In-ground growing of cool season greens (spinach, arugula, lettuce, etc.)

HOOP HOUSE CONSTRUCTION AND COST

Here is a 60-second time-lapse video of a larger hoop house construction:.

Here’s an overview of the construction process:

CONSTRUCTION COSTS

Here is a complete materials list and costs for an individually applicable 11’ wide x 15’ long x 8’ high walk-in hoop house design. This design can be enlarged or decreased by simply adding or removing hoops and associated materials. We will enlarge them (see below) to 90′ long. Be certain to have accurate measurements for determining plastic size before ordering!

MATERIAL DESCRIPTION PRICE QTY/House TOTAL
PVC 20′x3/4″ PVC schedule 40 plumbing pipe $4.57 6 $27.42
Gray Conduit* 10’x1 ¼” gray conduit schedule 80* $5.85 12 $70.20
Wood Stabilizers 1x6x8′ pressure treated (cut to 1×3’s) $8.97 6 $53.82
Wood 2×4′ stud (cut into 1×2’s) $2.25 3 $6.75
Wood 1x4x12′ pressure treated $8.77 2 $17.54
Wood 2x4x16′ (cut into 2x2s) $7.06 1 $7.06
Posts 8′ Steel “T” fence post $5.77 4 $23.08
Rebar Anchors 20’x½” (cut as needed – based on soil consistency) $7.10 1 $7.10
Ties 8” plastic zip ties – 100 $8.97 1 $8.97
Screws 1 ¼” x   5lb drywall screws $21.97 1 $21.97
Wire for X Braces 16 gauge galvanized utility wire – 25′ roll $6.47 1 $6.47
Staples 3/8″ t-50 staples – 1250/pack $3.22 1 $3.22
Plastic*** 6 mm IRAD poly film 25’x35′ sheet $150.00 1 $150.00
Plywood For reinforcements… scrounged  –  –  –
 TOTAL/HOUSE $376.18
 BUDGETED TOTAL** $500.00

* Gray conduit is a sturdier option and is also UV resistant, resulting in extended longevity over standard white PVC. This is beneficial because PVC is susceptible to brittleness and breakage over time due to UV degradation. Prices include sizes of 1″, 1 ¼”: and 1 ½”. Because it comes in 10′ lengths instead of 20′ lengths, use the bell end of one of the lengths to join the two 10′ lengths for a single 20′ piece. We will likely use 1″ or 1 ¼” for the hoop bows.

** For budgeting $500.00/hoop house, no shipping has been included. The one exception would be for IRAD film. IRAD film will be shipped and shipping price is included in sheet pricing. The budgeting cushion is for other missed expenses and taxes for components other than IRAD film (No tax has been assessed by our IRAD seller) and allows us to expand each house on-site (if deemed necessary) while remaining within our budget parameters.

*** Be sure to check and double check that your plastic size is correct. Cutting fees can range from $12-$20/cut. Cut your own on-site from a roll to avoid this charge. Here is one way to calculate the size of plastic required:

Width of plastic is determined by these hoop house structural measurements:  Width + Height + 2′ (round to standard width size – always good to have more than not enough)

Using this formula our 11’ wide x 15’ long x 8’ high hoop houses would require a plastic width of 21’ (11+8+2 = 21’). So we would buy a 22’ wide plastic roll.

Length of plastic is determined by these hoop house structural measurements:  Length + Height + Height + 2′ (assuming the cover is bottom to bottom including both end walls)

Using this formula our 11’ wide x 15’ long x 8’ high hoop houses would require a plastic length  of 35’ (15+8+8+2 = 33’). So we are calculating a 35’ length. Thus, one sheet of 22’x35′ IRAD poly film ($150) will cover one hoop house this size and we are ordering two 22’ x 105’ rolls that will provide for 3 of our starter houses per each roll, so enough for 6 hoop houses total. 

This formula will give you some leeway with the plastic; yes there will be some leftovers, but if you are short, you will have to reorder or downsize your hoop house. Also, be careful when using online calculators as they generally provide surface area measurements and may or may not include built-in leeway, and you do want at least one foot excess on all sides so you can stretch the plastic taut.

MORE HOOP HOUSE PLASTIC INFORMATION

Here’s a link talking about the best plastics for greenhouses: Click Here.

Based on our own research, UV-treated polyethylene (or IR film which greatly reduces or eliminates interior condensation and is about $0.02 more per square foot over standard UV treated polyethylene film) is our recommended choice for hoop houses due to durability and eliminating the yearly labor replacement efforts of non-UV plastic. The UV-treated is guaranteed by most wholesalers for 4 years, some stating that many consumers report a longevity of 6-7 years.

We have not substantiated this claim and will determine its true longevity over time. It can be ordered in rolls from 6’-64’ wide. Most companies carry rolls 100’ in length or more and some cut to whatever your desired length, 1000’ or more. When ordering in large quantities, the square foot price is $0.10 – $0.12 cents/sq. ft. Prices are quoted both by the square foot and lineal foot. Some distributors will offer dealer pricing which will decrease the overall price. Most large sellers seem to have only a fractional difference in price. Shipping is variable, 15-20% of the cost is a guideline but exact rates can be determined at the time of your order placement. Some offer prepaid shipment over 3000 lbs. Small orders under 21’ widths are generally shipped UPS while 21’ widths and larger are by semi-trucks. Global shipping is done by many. Six mil polyethylene is also referred to as 150 micron poly, depending on your geographic location. Some websites provide prices but due to fluctuations, you will have to order via phone for up-to-date pricing.

Though there are numerous suppliers worldwide, here are four that we researched:

Gempler’s: Website  ::  Customer Service: (800) 382-8473  ::  Technical Support: 800-874-4755
FarmTex: Website  ::  (800) 327-6835
U.S. Global Resources: Website  ::  (206) 722-3999
Gothic Arch Greenhouses: Website  ::  (800) 531-4769

No matter who you contact, check for the closest dealer to minimize shipping costs. Order larger quantities for better price breaks.

We also researched 6mm polycarbonate from China that claims to have a 10 year warranty. We spoke to several US vendors and they said this new flexible polycarbonate plastic is not as durable as stated. We’re not sure if this is accurate or marketing for their advantage.

Three hoop house videos with a wealth of hoop house information we think most people will find useful:

LARGE SCALE GROUND-BASED HOOP HOUSE CREATION

For large-scale ground-based hoop house creation, the most space and resource efficient designs we identified were two 90-foot hoop houses placed end to end to form a 180′ row. Using this layout we calculated we could easily place 9 rows per acre and two acres (0.809 hectares) of rows to maximize space usage. Rebar and tubing would be spaced on 3′ centers. The following prices were calculated (current as of September 2013).

MATERIAL DESCRIPTION PRICE QTY/ROW ROWS TOTAL
Rebar 1/2″ X 20′ #4 = five 4ft pcs $6.35 25 18 $2,858
PVC 3/4″ X 10′ Sched 40  $2.28 122 18 $5,007
Plastic Polycarbonate 12′ X 110′ roll $148 1 18 $2,664
 TOTAL $10,529
 +30%* $3,159
 GRAND TOTAL $13,688

* 30% has been added to these costs to cover tax, shipping, and/or other expenses we may have missed.

2 ACRES OF HOOP HOUSES PRODUCTION CALCULATIONS

We also calculated the food production of building nine 180 foot (54.864 m) rows of hoop houses per acre. To do this, we sourced university studies on hoop house production averages and then calculated the amount of food produced based on the maximum of two acres (0.809 hectares) of growing space we would initially dedicate to hoop houses:

FOOD University Row Projections % of Row Lbs Produced/Acre Acres TOTAL
Potatoes 1,440 lbs/180 ft row 100%  1,440 lbs 2 2,880 lbs
Squashes (winter)  1,080 lbs/180 ft row 50% 540 lbs 2 1,080 lbs
Squashes (summer)  576 lbs/180 ft row 50% 288 lbs 2 576 lbs
Onions  1,584 lbs/180 ft row 100% 1,584 lbs 2 3,168 lbs
Cabbage 1,224 lbs/180 ft row 100%  1,224 lbs 2 2,448 lbs
Carrots 1,080 lbs/180 ft row 25% 270 lbs 2 540 lbs
Cherry Tomatoes  3,240 lbs/180 ft row 100% 3,240 lbs 2 6,480 lbs
Beets  720 lbs/180 ft row 50% 360 lbs 2 720 lbs
Broccoli  375 lbs/180 ft row 50% 187 lbs 2 374 lbs
Cucumber  1,224 lbs/180 ft row 50% 612 lbs 2 1,224 lbs
Garlic 250 lbs/180 ft row 50% 125 lbs 2 250 lbs
Lettuce 600 lbs/180 ft row 50% 300 lbs 2 600 lbs
Pumpkin 1,080 lbs/180 ft row 50% 540 lbs 2 1,080 lbs
Radish 216 lbs/180 ft row 25% 54 bs 2 108 lbs
Melons 144 lbs/180 ft row 50% 72 lbs 2 144 lbs
TOTAL 21,674 lbs

Note: The foods listed are not the comprehensive list of what we would recommend growing, but rather a close estimate of the space (% of rows) we would recommend dedicating to foods that produce similar types and quantities of food. In accordance with our open source botanical garden model, we suggest growing the broadest diversity of foods possible for maximum biological and culinary diversity and to identify which species of different foods do best in your area.

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Reference Links:

This open source hub includes the following sections:

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