Hoop House Calculator - DIY Greenhouse Plans
Plan your DIY hoop house or high tunnel project. Calculate the number of hoops, pipe length, and plastic sheeting size needed for your garden structure.
Structure Dimensions
Material List
What is a Hoop House?
A Hoop House, also widely known as a high tunnel or polytunnel, is a simple, cost-effective greenhouse structure used by home gardeners and commercial farmers to extend the growing season. Unlike a traditional greenhouse, a hoop house is typically unheated, built directly over the soil, and uses passive solar energy to warm the ground and air.
The structure consists of a series of arches (hoops) made from PVC pipe or metal conduit, covered with UV-resistant greenhouse plastic. Because they are inexpensive to build and easy to construct, they are the perfect entry point for year-round gardening.
Hoop houses are excellent for:
- Season Extension: Plant cool-weather crops (lettuce, spinach, kale) weeks earlier in spring and harvest late into winter.
- Crop Protection: Shield tender plants from frost, hail, wind, heavy rain, and pests.
- Increased Yields: The warmer environment accelerates plant growth and fruit ripening for tomatoes and peppers.
To plan the layout of your garden beds inside the hoop house, check out our Lawn to Garden Conversion Calculator for soil and planning tips.
For enriching your soil naturally, explore our Composting Calculator to estimate compost production.
To secure your garden perimeter, use our Fence Calculator to plan protective fencing.
For raising chickens nearby, try our Chicken Coop Size Calculator to design the perfect coop.
To estimate bulk material needs for beds, check our Cubic Yard Calculator for soil and mulch.
How the Calculation Works
This calculator uses basic geometry to design a "Quonset" style (semicircular) hoop house. Here is the math behind the materials list:
Hoop Length: Assuming a semicircle, the hoop length is half the circumference of a circle.
Length = (π × Width) / 2.
Number of Hoops: Determined by the length of your house and your chosen spacing.
Hoops = (Length / Spacing) + 1 (We add 1 for the end hoop).
Plastic Size: We calculate the total width needed to cover the arc plus extra for securing to the ground (wiggle wire or burying). The length covers the top plus the end walls.
Key Concepts Explained
Purlin
A horizontal bar (pipe or wood) running the full length of the roof's peak. It connects all hoops, preventing them from swaying and adding crucial strength against snow load.
Ground Sleeves
Short sections of larger pipe pounded into the ground. The hoop pipes slide inside these sleeves, anchoring the structure securely.
Wiggle Wire
The professional way to attach plastic. A metal channel is screwed to the frame, and a zig-zag wire spring locks the plastic into the channel tightly.
Roll-Up Sides
A ventilation system where the side plastic is attached to a pipe that can be cranked up, allowing airflow across the plants on hot days.
How to Use This Calculator
Measure Space
Determine the maximum available length and width in your garden.
Choose Width
Select a width. 10ft or 12ft are common sizes that fit standard pipe lengths efficiently.
Select Spacing
Choose 4ft for standard builds. Use 3ft spacing if you live in an area with heavy snow or strong winds.
Calculate
View your shopping list for pipe lengths and plastic dimensions.
Benefits of Using This Calculator
- • Reduce Material Waste: Calculating the exact arc length prevents you from buying 20ft pipes when you only needed 15ft, or buying a plastic sheet that is 2 feet too narrow.
- • Ensure Structural Safety: By helping you visualize hoop spacing, you can ensure you have enough support arches to withstand local weather conditions.
- • Accurate Budgeting: Knowing the total footage of pipe and size of plastic allows you to price out the project accurately before heading to the hardware store.
Factors That Affect Your Results
1. Pipe Diameter & Material
For small low tunnels, 1/2" PVC is fine. For walk-in hoop houses up to 12ft wide, 1" or 1.25" PVC works. For structures wider than 12ft, you MUST use metal top rail or conduit to prevent collapse under snow/wind load.
2. Plastic Securing Method
We add extra plastic to the dimensions for securing. If you plan to bury the edges in the soil (a common method), you need at least 1-2 feet of extra plastic on each side.
Frequently Asked Questions (FAQ)
Q: What is the best direction to orient a hoop house?
A: East-West orientation generally provides the most consistent light for winter growing, maximizing solar gain on the south side. North-South provides even light distribution for summer crops but captures less heat in winter.
Q: How do I ventilate a hoop house?
A: Ventilation is critical to prevent overheating. The simplest method is roll-up sides. You can attach the plastic to a pipe running along the bottom edge and roll it up manually on hot days. Doors at both ends also create a cross-breeze.
Q: Does the plastic need UV protection?
A: Yes! Regular construction plastic (like 6-mil clear Visqueen from hardware stores) will degrade and fall apart in a few months. Always use 6-mil UV-rated greenhouse plastic, which is designed to last 4+ years in direct sunlight.
Q: Can I heat a hoop house?
A: Yes, but because they have little insulation (R-value ~1), they lose heat fast. Row covers inside the hoop house (creating a double layer) are often more efficient than heating the whole air volume. Some growers use thermal mass (water barrels) to store daytime heat.