This job is best done in mild sunny weather, when the plastic will be dry can stretch some but not too much. Arrange for a windless day to spread plastic – that is, less than 5mph winds, tops! If necessary do the plastic spreading at dusk, when the wind drops. Or at dawn in summer, but not in cold weather.
Order the right size and type of plastic in good time. We use 48-foot x 100-foot Tufflite IV and Tufflite Dripless for our 30-foot x 96-foot gothic tunnel. Our plastic goes to the ground (no separate sidewalls). For the end walls we buy 24’ x 100’ for a double layer on each end. I have not tried the extra-strong Solaroof and Solarlite woven multilayer materials. We use the wigglewire and aluminum channels (also called Polylock).
Gather enough people. We like six or seven people with good common sense, who are willing to take directions. It helps if some of them have done the job before.
Mistake No. 1
We put up our hoophouse in the fall of 2003. Initially we pulled the plastic too tight, and the screws that held the wigglewire channel to the Eastern Red Cedar baseboards gave up and popped off. I recommend people to bolt the wigglewire channel through the baseboards from day one. We dealt with our problem by adding metal strip battens that fit inside the channel over the plastic and the wigglewire, and bolted them all the way through the baseboard. We knew this meant we’d have a longer job when we changed the plastic as we’d have to remove all the battens. That time came in 2007.
Mistake No. 2
The first few years of our hoophouse we had good inflation. Then the pressure dropped and we concluded that we had too many holes in the plastic, up where we couldn’t see them. That prompted us to change the plastic in 2007, rather than 2008 as we’d hoped to do. But the pressure never did get back up to a reliable level. We decided we needed a new inflation fan. That didn’t help. Later we found that the new fan had a lower output than the original, so we got another new one with the higher output of 60 cubic feet per minute (cfm) (hey, plenty of spares now!).
Mistake No. 3
In 2007, we removed the battens and bolts, many of which had rusted. It was slow and frustrating work. We then bolted the channels to the baseboards “forever” and put on the new plastic. That time we left more slack in the outer plastic – too much. We went back and removed some of the slack. We thought we didn’t really need to replace the plastic every 4 years. We decided to go for 5, but buy the plastic and store it in the shed in year 4 just in case. Well, year 5 was busy. We switched the big plastic in September 2013 (year 6).
Mistake No. 4
2013 was also busy, so we decided to just do the roof plastic that year and do the end plastic the next year. Several of the baseboards were rotted, so we also had to replace those. We had termites too. Removing the old baseboards involved removing more rusty bolts. Another slow frustrating job. Good thing we weren’t doing the end walls too! We also took the opportunity to add diagonal braces to the windward end of the frame, as the end wall had started to lean in. This time we made the opposite mistake with the plastic - we pulled the plastic too tight and trimmed it before we realized. We tried loosening it the next day, but the wigglewire and the pliers had made a lot of holes. We used a lot of Polypatch tape. It never gave us very good inflation. Then we got a hailstorm. Rare in this part of the country, but we think it made holes.
Near-Miss No. 1
In 2014 we replaced the end wall plastic. Happily we noticed just in time that we should not cut the 24’ plastic in half at 12’, otherwise both pieces would have been too short to reach the peak. We went with the outside being in one piece, and the inside having a seam across just above the apex window. You could, of course, buy bigger plastic! It’s easiest to plastic the whole end wall, then cut out the doors and windows. With luck, the cutout pieces will serve to cover the door and window frames. It helps to have two people “hanging” the plastic at each end, to be sure of getting it hanging plumb and covering all the corners. Use lengths of wigglewire to tack the plastic into the channel, just fastening a few wiggles in the middle of each length. Then batten the plastic onto the framing before finally setting the wigglewire in place and trimming off the extra plastic. The inner end wall plastic goes up and over the metal tubing to fit in the channel on the outside of the wall.
When we replaced the end-wall plastic we used separate wigglewire for the ends and for the roof plastic – a good decision. We made sure to put the roof plastic on the outside relative to the wall plastic, for better weatherproofing, and to make life easier when replacing the roof plastic. (We figured ends can go longer without new plastic – they are not inflated, so a few holes don’t matter, and most of the punctures happen to the big roof plastic anyway.)
Near-Miss No. 2
In 2015 we had very floppy plastic, but little enthusiasm for changing the plastic, especially given the troubles we had experienced with rusty bolts in 2007 and 2013, and miscommunication in 2013 about how tight the plastic should be. We hoped to wait till 2016 to replace the roof plastic. But it became apparent that the hoophouse would be much colder in the winter without the insulating air bubble, and the flapping plastic would have less strength against winds and snow. In the winter of 2014-2015 we’d had a really vicious cold snap – we had to use inner rowcover to protect the greens for the first time ever. No saying it wouldn’t happen again in 2015-2016. We reluctantly agreed we had to do something. Aha! We decided to change just the outer plastic! Perhaps the inner plastic would last round until we’d got at least 4 years from the new outer plastic? It would be easier just sliding new outer plastic over the inner layer that is already there. It would only be half the job! And we wouldn’t be tackling any baseboard problems or rusty bolts.
Pam Dawling lives in Virginia at Twin Oaks Community, an egalitarian, secular, income-sharing, work-sharing ecovillage established in 1967. There she helps grow food for around 100 people on three and a half acres and provides training in sustainable vegetable production for community members, practicing farming with awareness of ecology, finite resources and the future of the planet. Pam is the author of Sustainable Market Farming. Read all of her MOTHER EARTH NEWS posts here.
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