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How to Build or Buy a High Tunnel

Learn How to Build a High Tunnel on Your Small Farm

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Inside a high tunnel.

Inside a high tunnel.

Photo © USDA

If you are a small farmer in business, a hobby farmer, or a homesteader, especially in a cool climate, you might want to expand your growing options by buying or building a high tunnel or hoophouse.

What is a High Tunnel or Hoophouse?

These terms refer to the same thing: a large, solar heated greenhouse used to extend the growing season. There is no electrical or automated ventilation in a high tunnel or hoophouse. High tunnels and hoophouses generally have ribs made of metal or PVC (plastic), and are covered with clear plastic. Crops are grown in the ground with drip irrigation.

High tunnels differ from greenhouses in that greenhouses typically have active heating and electrical power, while high tunnels just use the sun for heat and wind or passive ventilation such as lifting the sides, for ventilation. High tunnels are generally more mobile and less complicated than greenhouses.

Why Choose a High Tunnel?

High tunnels can extend the season and allow small farmers to produce crops in the off-season, when demand is higher. With an extended growing season, yield overall is increased, but high tunnels also offer better quality produce and higher yield in a given amount of time.

High tunnels protect crops from wind and low temperatures. They also reduce weed problems, as most crops are grown with plastic mulch and drip irrigation. Without natural rainwater, soil in between crops is not overly moist, so weeds don't get started.

High tunnels also protect crops from damage from birds and deer. Screens, if used, can help protect crops from insects.

Low tunnels are more portable, smaller versions of high tunnels that you can't stand up in. They are generally used primarily for season extension. Being able to stand up in and work inside a high tunnel takes everything to another level.

Buying a High Tunnel

You can buy the frame structure and plastic of a high tunnel already made. The cost is approximately $0.75 to $1.50 per square foot. However, you need to add an additional 25% or more for site preparation, water lines for irrigation, lumber for end walls and other miscellaneous items.

The US Department of Agriculture has a program giving grants for high tunnels to qualifying small farmers. Find out more here:

Building a High Tunnel

If you are the DIY type, you may choose to build your own high tunnel. You will still have to purchase the metal or PVC for the hoops as well as the plastic. You can use various methods to anchor the high tunnel to the ground, to bend the hoops, and to secure the plastic cover to the hoops as well as allow for ventilation.

Sizing a High Tunnel

High tunnels are typically ten to thirty feet long and eight feet wide. They are nine to twelve feet high with either three- or five-foot sidewalls. But, high tunnels come in many shapes and sizes and can have multiple bays that share sidewalls. They can also be built into hills or against existing walls.

Placing a High Tunnel

You will need to choose the site for your high tunnel. The site should be level, well-drained and easily accessible. You can move high tunnels as desired each year, or you may choose to keep the high tunnel in one location. If you are using the high tunnel in one location, plan to amend the soil each year to maintain fertility. You can also used raised beds or tables within a high tunnel (for example, you could grow microgreens or start seeds on tables in a high tunnel).

North-south or east-west orientation for light is not as critical with a high tunnel as with a greenhouse. The main consideration is the direction of the prevailing wind on your farm. Because there is no automatic ventilation, the wind provides the ventilation for your high tunnel. The general recommendation is to orient the high tunnel perpendicular to the prevailing winds.

High Tunnel Regulations

As a general rule, high tunnels are considered impermanent structures, so you probably won't need to get a permit for your high tunnel. However, it's best to begin by checking with your local zoning regulator to find out what the laws are in your area.

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