High Tunnel Construction Processes and Considerations With Miami County Conservation District Claire Zimmermann & Jacob Chapman Site Selection • Accessibility • Space • Water/power access • Light optimization for winter harvest • Stacked or singular? • 40° latitude and south, north-south recommended Wind and High Tunnels • Orientation • NS or EW? • Lift • Windbreaks • Ventilation Grading • Facilitates mechanization • Consistent irrigation • If not moveable, will have inconsistent vertical growing space Waterflow • Will displace rainfall • Will enter hightunnel if not directed • Use drainage aisles Soil • Amend soil first • Well drained soils are best Build Process • Side walls (with base board and hip boards) • Hoops ( with hoops, trusses, and collar ties) • Purlins • Plastic • End walls • Lots of hardware like brace bands, collar ties, cross connectors, etc… Ordering Choose your supplier • Advantages to each Know what is included • Lumber or end walls may not be included with all Pick-Up/Delivery • Delivery can be a significant added cost • Local suppliers are advantageous • Have build site prepared • Site for construction and site for staging • Vehicle accessibility • Site for staging • Site for construction • Trusses • Sidewalls • Endwalls • Pulling plastic Pre-Build Organization • Instructions! • Parts list – triple check • Read instructions (twice) • Reference online tutorials • Set up guide strings • Set up jig for trusses • Prepare space boards Build Days • Some jobs require 1, 2 or at a minimum 3 people! • If you have a full crew of folks, can be completed in 3-4 days • If you know it will take longer, make sure you have planned stopping points that won’t compromise your structure Build Pipe Skid Assembly Build Trusses • Setting up jig is necessary • For strength • For alignment • For consistency • Use guide strings • Trusses have hoops, trusses and collar ties • Number your trusses, my HT has 13! • Trusses will require different number of brace bands and, endwall hoops will not have trusses • Ensure consistent spacing on all hoops! • No self tapping screws on the exterior of the high tunnel! Installing Hoops • Lay out hoops in order • A minimum of three strong people needed who are comfortable and SAFE working at heights • Three points of contact when at heights • People working up top should never bear the weight of a hoop, only guide • Heavy lifting is done from the ground, 5-6 people is ideal • Two truck beds are very helpful • Don’t attempt when windy, there is inclement weather, or if you are tired • Position side walls (skid assemblies) using guide string and brace in an upright position (make sure those brace bands are on there and orientation is correct) Installing Hoops • Install hoops in sets of three • End wall hoops should be quickly tied into the rest of the hightunnel, as they are less structural • Install Ridge and collar tie purlins before proceeding to next hoops • Best practice is to mark on each pieces hoop and collar tie where purlin should land • Use Spacer board again to ensure consistent spacing once up • Set all seams before moving on to next set! • Make sure brace bands are where they need to be! Bracing • Will vary greatly from company to company • Should be bracing for both side walls and hoops • Cable bracing is also an option • Bracing can make or break a hightunnel • Movable and larger hightunnels generally require more bracing Endwalls • Many different configurations and options • Is the high tunnel moveable? • What type of equipment do you plan to operate in high tunnel? • Do you need accessibility on both ends or just one? • Ventilation? • We built in place Anchoring • Every side wall is anchored except the center most • Unanchored high tunnels will fly away • Consider securing anchors in cement, and or, add weed barrier, minding anchors location while using equipment is problematic • Need anchors in every planned location for high tunnel Plastic Install • Many methods • We’ve done two, both with success! • First, install all tracking for wiggle wire, secure well! • some areas channel will be used twice, depending if you install one continuous piece or multiple peices • Roof • Endwalls • sidewalls • No wind over 5mph, need to watch weather closely • Need a team of at least three, again 5-6 is better • Getting a tight fit is key • Plastic is constricted in cold weather, will loosen once it warms up Time to plant! In review Questions?
