Introduction

Vegetable growers can benefit greatly from the installation of high tunnels on their farms. High tunnels are seasonal, polyethylene or polycarbonate covered structures used to extend growing seasons. Unlike greenhouses, no mechanical ventilation or heating systems are needed, and crops are grown directly in the soil. High tunnels can also help improve crop management and production through better moisture control and reduced issues with nutrient and pesticide runoff, diseases, pests, and wildlife. Each high tunnel manufacturer has specific guidelines to follow for the installation and maintenance of their product. Landowners who participate in USDA-Natural Resources Conservation Service (NRCS) Farm Bill programs are required to follow these guidelines in order to have successful projects. This document has been designed specifically to aid landowners interested in installing high tunnels on their own, instead of using a contractor. It is not intended as a substitution for the NRCS Construction Specifications or manufacturer's instructions but a supplemental with easy-to-follow photographic images and diagrams. Planning NRCS is available to provide technical assistance to landowners in planning and installing high tunnels. Assistance regularly includes guidance with site selection and high tunnel model selection for your operation, pre-construction meetings, daily inspections, and final inspections. Financial assistance is also available through NRCS on a competitive basis. NRCS may also recommend other best management practices to accompany the high tunnel in order to protect other natural resources. Many factors should be considered when choosing the installation site. A relatively flat area with well-drained, high quality soils is best. The site also needs to be accessible throughout the year and have a water source for irrigation. It is important to choose an area that will not be significantly impacted by heavy winds, runoff, and flooding. Any runoff from the high tunnel and

Interior of High Tunnel

High Tunnel with Roll-up Sides

Recently Constructed High Tunnel

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adjacent lands should be diverted from the unit to prevent damage to crops and the structure. Orienting your house in a north-south direction can maximize the sunlight received, and care should be taken to consider the impacts of shade from surrounding trees. Meeting these general site requirements may require changes in how you manage your property, but should result in a long-lived and productive high tunnel structure. Carefully consider how your daily routines will be impacted by the high tunnel. Select a model that meets the size of your planned operation, that has the load-bearing strength to withstand normal high winds for your location, and that is easy to install. Determine if you want the high tunnel to be mobile or fixed. You may also consider consulting with producrs in the area that have recently installed high tunnels for advice prior to purchasing.

Depending on the high tunnel kit you choose, installation instructions will vary. When participating in NRCS programs, you will be required to install the high tunnel in accordance with the recommendations of the manufacturer. Due to the variation among kits, this document focuses on the general step-wise installation process that most kits have in common. When the high tunnel kit arrives, double check that it is the model you ordered. Read through the manufacturer's instructions and/or watch the manufacturer's instructional video(s) to make sure you understand the step-wise installation process. Sort through the components and make sure you have all the pieces and can identify their role and location, prior to getting started with installation. See the image below for common parts of a high tunnel.

Site Preparation and Excavation

Once you have received your high tunnel kit and have decided on a location, the site must be prepared. This includes the removal of all grasses, trees, stumps, roots, brush, weeds, and other objectionable materials. You will also want to make sure the site is as level as possible.

After preparing the high tunnel footprint, install four corner stakes corresponding to the length and width of the unit. Square the stakes (right angles) by measuring diagonally and utilizing a carpenter’s square.

Foundation Posts Once the corner stakes are in place and square, install the corner foundation posts. Depending on the type of post material and local soil conditions, you may be instructed to pound the posts by hand, use a post-pounder, or use an auger and concrete. Be careful not to damage post tops during the installation process. Regardless of the method used, ensure the corner posts are put into the ground both level and plumb.

Concrete HUA Pad

HUA – Feeding Area

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After installing the corner foundation posts, pull a string between the posts as a guide in marking the location of the side posts. Use the same installation method you used for the corner post, ensuring that the posts are straight and level. Erecting the Structure The bows (depicted below) are the semi-circular to triangular ribs of the structure that fit into the foundation posts. These are generally installed prior to the purlines, hip boards, and baseboards, which connect and support the bows. At times, the bows come in several pieces in high tunnel kits and require assembly. Assemble the bows, including any truss supports and truss braces, according to the manufacturer's instructions. After the bows are assembled, they should be attached to the foundation posts. Bow installation steps will vary depending on the model and manufacturer.

After all the bows have been erected, the purlines are installed to connect and support the bows. Often, a purline is used to add stability along the top ridge of the bows and/or along both sides of the top. You will likely need a ladder for this step. The next step is to ensure both end bows are plumb. If the ends are not plumb, they can be pulled from the top ridge of the end bow to achieve a plumb state and held into place before further stabilizing the structure. Once a plumb state is achieved, baseboard installation should follow. Baseboards, commonly two-by-ten boards, connect and reinforce the foundation posts along the ground. Baseboard installation methods vary, but generally pipe straps are used to attach the foundation pipes to the baseboards. These are attached one at a time, and individual baseboards are connected to each other with a reinforcement board. Continue the process until the baseboards have been completed along both sides. Some kits come with wind braces while others have to be purchased separately. If wind braces are recommended for your site, install them after completing the baseboards. Now that the structure is stable, the installation of the hip boards can proceed. These serve as the bottom of the polyethylene roof and often house the mechanism for the roll-up sides. These are usually placed near the top of the foundation posts, or along the lower purline. Follow the kit instructions to see exactly where these are to be located for your high tunnel. Be careful to ensure they are level when attached so that the hip posts evenly bear the weight of the roll-up sides.

Placing the Bows in the Posts

Baseboard with Reinforcement Piece

Foundation Posts

Purline Installation

Baseboards with Reinforcement Board

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To complete the structure, the end walls need to be framed. It is critical to follow the instructions of your kit for this step, as the end walls construction varies widely between different kits. Some call for constructing the frame before erecting it, whereas others recommend constructing them upright. Kits also vary as how to anchor the end walls. Some call for the use of concrete, while others recommend trenching, and/or baseboard installation. Plastic Sheeting The task of putting on plastic sheeting requires a calm day with low winds. When installing the plastic layer, make sure to put the correct side of the plastic sheet on the inside. It will likely take several people and ladders to have a successful and easy installation. How the plastic sheeting attaches often depends on the kit. Some kits require battens to be nailed over the plastic to hold it in place. Many kits utilize wire locks to hold the plastic in place. For a wire lock to function properly, the plastic sheeting is placed in the interior of the wire lock structure and then a wire is used to lock the sheeting into place. Regardless of the method, ensure that the plastic sheeting is pulled tight and is as free of wrinkle as possible, prior to locking it into place. Finishing Up the High Tunnel Generally, the last steps toward completing your high tunnel involves installing the roll-up plastic sheeting for the lower side walls as well as any entry doors, roll-up doors, or shutter gables. These steps and kit accessories vary depending on the model used.

Hip Board with Mechanism to Lock in Plastic

Plastic Sheeting Installation

Plastic Sheet Fastening Using Wire Locks

Project Information: Funds for this project were provided by the USDA Natural Resources Conservation Service and administered by the Two Rivers RC&D Council.

Non-Discrimination Statement: The United States Department of Agriculture (USDA) is an equal opportunity provider and employer.

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