My High Tunnel is now a Low Tunnel

cole_robbie(6)December 6, 2013

Clearspan building in the background with no damage:

These are 4x4 posts set in concrete:

It looks like I should have taken the plastic off before winter :(

I think it can be fixed, though, at least enough to use. I can cut the chain link top rail hoops where they bent and re-attach them with sleeve clamps hopefully. Maybe our tractor can push the end walls closer to upright again. The plastic itself is fine. It would have done a lot less damage if the plastic had given out before the hoops.

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Ice storm?

    Bookmark   December 6, 2013 at 5:24PM
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sorry that happened to you. i put a claim in on my homeowners policy for a hoophouse collapsed by the wind and was very satisfied with the result. i was able to use 32' of the original 72' length. good luck.

    Bookmark   December 6, 2013 at 5:53PM
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in the future, if you know you got snow coming that could cause problems. you can put some heat in the hoophouse so the snow melts and slides off easier. it does not take much to keep it warm enough so the snow does not freeze and stick to the plastic. then it often slides right off and does not build up.

good luck on the recovery

    Bookmark   December 6, 2013 at 6:23PM
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Oh that sucks :(

    Bookmark   December 6, 2013 at 7:25PM
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Can you 'jack up' the ribs and put supports under them? Just an idea.

sorry for your loss, but it does look like you'll be able to save at least part of it.

That is one reason that Gothic works better with a snow, it will slide off easier.

    Bookmark   December 6, 2013 at 8:16PM
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Thanks. I think a lot of it can be salvaged. I am going down there tomorrow with my tools and start taking it apart. I think with a few sleeve clamps, I can put it back together.

I am mostly just amazed at how strong the plastic is. It was one sheet of 6-mil poly that had enough force to bend the 4x4 posts over like that as the snow pulled it in. The purlins broke right away where they were bolted into the composite board that made the end hoop, so that is just the plastic pulling the posts down like that. It's held on with a channel of wiggle wire. It's amazing to me that the plastic is stronger than the three middle 4x4 posts in concrete.

    Bookmark   December 7, 2013 at 12:08AM
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when there's frozen precip that accumulates more than a couple of inches i go out with a broom and sweep it off the hoophouses. what is the width of that tunnel? it looks like the weak point(s) of that design is where the bows meet the ground it not the ridge piece that's pulling down the 4x4 post?
do you have anything growing in there?

    Bookmark   December 7, 2013 at 5:58AM
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Kenny, this wasn't a normal snow storm.

We sometimes have to go out and 'encourage' the storm to slide, from the inside. I use a push broom and start from the bottom. Our plastic stretches enough so it bags between the ribs.

    Bookmark   December 7, 2013 at 9:35AM
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The top purlin was bolted to the composite decking board with a carriage bolt. It bent the bolt and ripped out the inch or so of composite board. It's not holding any tension right now. The plastic is still holding a lot of weight of the snow right now. I have to start detaching it to get to the middle to get the snow off.

That high tunnel is (or was) 18.5 x 48. The Clearspan building in the back is 14x48. It is made of a thicker gauge of pipe and snow does slide off a little easier, but it still will hold thousands of pounds of snow and ice.

The pic below is from last winter, before I built the top rail high tunnel:

That's a drift of wet, heavy snow almost four feet thick. It's probably ten thousand pounds that the one layer of 6-mil poly is holding.

Now that I know the top rail can't hold snow, I might have to re-think my design and my plan. Top rail might still be worth using, because it seems very strong against storms. Maybe I can make a much wider high tunnel if I just give up on snow load and take the plastic off every fall.

    Bookmark   December 7, 2013 at 1:23PM
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I think I would put in some posts to help hold that top rail. some 4x4s right under it.

    Bookmark   December 7, 2013 at 8:13PM
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jrslick (North Central Kansas, Zone 5B)

Just run 3, 16 foot 2 by 4's down the center, with 2 by 4 posts every 16 feet.

This will support the weight until you can sweep the snow off.

Here is an example, I have added an additional post and beam on either side also. This has worked for me.

Sorry for your loss.


    Bookmark   December 7, 2013 at 9:59PM
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Tough loss. Hopefully you can salvage most and prevent it from happening again. It's been a tough early winter so far!!

    Bookmark   December 10, 2013 at 2:01PM
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Hope you can get them back to work soon.
Good luck.

    Bookmark   February 24, 2014 at 1:20AM
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Thank you. I just got everything apart this week. A cordless reciprocating saw was a big help. My hoops are now a stack of pipes in my backyard. I hope to be able to cut off the pinched ends and sleeve clamp the pipes together to make new hoops. They won't look great, but I think it will work.

Here is a pic with the plastic off, before I took it apart:

    Bookmark   February 24, 2014 at 2:36AM
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that is sad looking. good luck cole.

    Bookmark   February 24, 2014 at 5:39AM
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Cole - For a stronger arch, make the middle of a single section with shorter pieces on the sides. A clamp in the middle will be weak.

The 2x4 supports look like a good idea too.

    Bookmark   March 1, 2014 at 8:16AM
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Sorry to see this Cole. I tend to agree with Lazygardens. If you purchased 1" pipe and bent it for your center peaks you could slide your 3/4" bows into those for added strength and tech-screw them secure.

I use a quick prop system not as reliable as Jay's but it is just a few dozen 1" slabs, etc just pushed under each side of alternate arches. After the snow slides off, the arches usually rise slightly so that a few of the boards fall. I need to cleck on them occasionally but those boards are stacked along both sides during the winter and in the growing season they are my walking paths between rows. They hold the sheet(s) of black plastic that covers my entire soil surface from moving and while picking I can slide my picking containers over them. Its just handy to keep old boards inside year-round.

    Bookmark   March 2, 2014 at 1:54PM
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Like old fashioned Clothes Line Props.

    Bookmark   March 2, 2014 at 3:43PM
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The top rail bows are 1 3/8". I think the conduit 90 degree elbows I cut in half to make 45s are one inch. Chain link top rail looks strong, but the metal is thin. I'm not going to leave the plastic on this structure again over winter.

I'm much more interested in gothic arch designs for a winter greenhouse, so that the snow slides off. I don't know how to build one out of top rail, but there are plans available for wood construction. Bending the wood for the arches looks like its own art form. I have read a lot about steaming boards to bend them. It is how boat hulls were built in ancient times.

Here is a link that might be useful: Gothic Arch plans

    Bookmark   March 2, 2014 at 7:47PM
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It is, maybe James can tell you. He was trained by the much older generation. His dad was trained by an older generation, so his knowledge is back to the 1880s or so. He's not that old tho, only in his 60s.

    Bookmark   March 2, 2014 at 8:40PM
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jrslick (North Central Kansas, Zone 5B)

Always wondered if something like this would work to make a gothic shape, with straight top rail pieces and then bend the top rail piece, with a hand pipe bender.

I was looking into this, earlier this year, I found a better option, but I can't find it now.

    Bookmark   March 2, 2014 at 11:53PM
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i have a hoop house that is made from chain link fence top rails and it was fine through 20"+ snow. i don't think its the materials that failed but the design.
i think this place has a jig that bends to a gothic shape.

Here is a link that might be useful: bending jigs

    Bookmark   March 3, 2014 at 5:03AM
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My Kaspersky Anti-Virus software doesn't like that link at all.

    Bookmark   March 3, 2014 at 10:11AM
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I bought my bender from lostcreek. I have the DY-20. It is supposed to make a 20-ft wide hoop from three 10' 6" pieces of top rail. My idea was to bend two pieces and connect them to a chain link post with a 45 degree conduit elbow, to mimic jrslick's design, at 18.5' wide. It works very well...until it snows, lol.

From what I can find, the lostcreek gothic design is a narrow one, 10-12' wide. It's the width and low profile of this building, which ironically makes it nearly invincible to wind, that makes it defenseless to snow. I know interior posts would have helped, but I didn't have the money for the lumber.

    Bookmark   March 3, 2014 at 3:11PM
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I am a little over halfway done rebuilding everything. I am getting good at patching together hoops from a pile of bent pipes. My cordless reciprocating saw is getting some good use. The high tunnel is 26 pieces of top rail; I bought 3 new ones. The rest will be the smashed pipes. It will be lumpy when I'm done, but it will still work.

I had high hopes for the sleeve clamps, but they are junk. They rip apart immediately under stress. I have had much better luck by cutting up pieces of 1.5" EMT conduit elbows. They fit over the outside of the top rail. I think I could use the elbows to make an A-frame with top rail quite easily. A gothic arch would be trickier, but by cutting sections of the EMT elbow, I can make sleeve clamps that are angled.

I'm surprised I hadn't read anything anywhere about connecting top rail with EMT elbows. It is easy and cheap. A 1.5" 90 degree elbow is about $4. Cut in half, it makes two nice 45 degree elbows. Tek screws hold it all together. If the same EMT pieces were sold as special greenhouse connectors, they would be 10x the price.

    Bookmark   April 9, 2014 at 10:57PM
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Good tip on the emt elbows, Cole_robbie.

    Bookmark   April 10, 2014 at 1:28AM
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