Many high tunnel vendors offer only the frame of the structure. In addition to the frame and its related shipping cost, many other costs, such as end walls, doors, etc. must be taken into consideration. The cost of the end walls will be determined by the size of the structure as well as the type of material used. End walls can be covered relatively inexpensively with 6 mil greenhouse plastic, or more expensive (and more permanent) options such as exterior grade plywood or clear polycarbonate panels.
End walls are often framed with 2x4’s using 24” centers since they are not load bearing walls. Many growers use 4x4’s on either side of the doorways. The cost of the lumber to frame the end walls will be dependent upon the width and height of the tunnel.
Other Lumber costs: 2x12 lumber (or two 2x6’s stacked side by side) will also be needed for kickboards at the base of the frame. This lumber will be in constant contact with the soil. Therefore, this must be taken into consideration when selecting the type of wood to use. Cedar lumber will last longer but at a much higher cost. The hip boards on the sides of the tunnel can be constructed with 2x6 lumber since they will not be in contact with the ground.
Doors: The type of doors you install will be determined by the type of equipment you plan to use in the tunnel. A small tractor may require an overhead door or large double doors while a much smaller door can accommodate a rototiller. Therefore, cost of doors will vary from grower to grower.