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High tunnels side by side = how close together?

Posted by ajsmama 5b (NW CT) (My Page) on
Fri, Aug 23, 13 at 1:46

I can't fit a long tunnel so I'm thinking two 50 ft tunnels side by side - 14ft wide hoops so is 30ft wide enough (my uncle who is leveling land figured) or should they be farther apart? I was pretty sure they should be farther apart but can't find how far. Again, orientation of land is such that they will be running N-S so I hate to block most of the afternoon sun off the eastern one.

Maybe I can figure posts down the center and do cross bracing and a peak to turn the 14ft wide hoops into a 30ft wide Gothic with 2 bays?


Follow-Up Postings:

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RE: High tunnels side by side = how close together?

leave enough space between to be able to clean away the snow if it gets very deep.


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RE: High tunnels side by side = how close together?

I'd leave enough room to mow between. Here, the multiple bay greenhouse, don't leave any room. We usually don't get enough snow to worry about, the heat melts it faster.


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RE: High tunnels side by side = how close together?

I'm wondering if there's a problem with structure or tall crops in one (probably the western one) blocking sun off the other, esp. since they would be running N-S, small rise to the south (though shouldn't block too much sun in spring/summer since by the time the sun moves to the end it will be high enough). Some woods to the east but I'm trying to keep the tunnels far enough away that they won't be in shade much of the morning. Pretty much due north of where I have the fenced-off raised beds now (and they get enough sun), just this 1 outcropping of ledge in between.

Not planning on using them during the winter - in fact would like to take the plastic off so I don't have to worry about snow.


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RE: High tunnels side by side = how close together?

Well, I have a little hand work to do in the corners but I now have a level pad (1" drop in 30ft, 6" in 64ft) and just have to decide how to run the tunnels - N/S 2 64ft tunnels close together or E/W 30ft tunnels maybe 3-4 of them. Any larger area would have required bringing in fill.


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RE: High tunnels side by side = how close together?

I would go with the N/S, it's always the best for even sun exposure. But if the tunnels are permanent you will need to get between and weed or mow. There is the problem of one of the houses shading the other of course. I would go with a distance that is at least a 45 degree angle from the peak of the other greenhouse. That should be far enough that the top of one greenhouse won't shade the near sidewall of the other too much.


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RE: High tunnels side by side = how close together?

Congrats on getting the pad leveled.

I'd go with the N/S, and if you don't want to use the entire house at one time, you CAN make a drop curtain somewhere inside to divide the house. Makes it easier to heat a smaller area if you wish. Just a big sheet of plastic or pieces made into, and clipped/taped onto the ribs.


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RE: High tunnels side by side = how close together?

I think I would easily use a 50-64ft long 14ft wide tunnel all at once - I usually have at least 250-300ft of tomatoes and peppers down there each year, the peppers esp. would be nice to get in early so they can ripen (or just have bells get big) before the end of Sept! I'm even thinking covering 1 tunnel in March/April to warm the soil and plant out in April/May, then uncovering once the tomatoes get going and it gets warm, putting the plastic on the other tunnel for a 2nd crop to continue into the fall?

If I go N-S then 2 tunnels are only going to be 2ft apart, just can't get leveled any bigger area than that without bringing in fill. Hate to put up only 1 tunnel and use half the area, but guess we could level another area just downhill (to the east) of that once the manure pile is moved. This was just a rare chance to get it done without paying for equipment to be brought in since my uncle wanted to use his dozer near the tree stand behind our house. I don't know yet if he's going to charge me for the 2 hours of work, but I'm hoping he will consider it payment for 13 years (and counting) of allowing him to hunt here?

Now I just need to lay out the baseboards and get them pinned into the ground before it freezes, lay out the beds and move the manure in to make raised beds before we put the hoops up - I figure we can put the hoops up any time, even right before the plastic goes on in the spring. No reason to put them up before winter since I'm not growing a winter crop (nor will I ever - I don't want to have to plow my way out there). But we can get the beds put in this fall to save time - just use the same landscape fabric that's covering the manure pile now to cover the tunnel/bed area, I think I have enough. I've got to get some burlap anyway for the other garden areas, so if it's a little short I can cover with that.


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RE: High tunnels side by side = how close together?

Typically, the baseboards are assembled after the hoops. It's ground stakes, hoops, center purlin, and then baseboards. The baseboards are mostly for attaching plastic and sealing the bottom edge. The ground stakes should hold the hoops down independently of the baseboards.


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RE: High tunnels side by side = how close together?

Get the hoops up before winter and anything else that might need pounded in. Yes do the hoops before the baseboards, just because you might be off alittle and you can adjust as you put the boards down. I would trust just the ground stakes, especially with your ground. the band boards add additional weight to help hold the rest down during very high winds. Ours have survived 80 mph winds so far without any problems, except the doors buckling, but the house stood, even the plastic. We do keep the shade cloth up year around for extra protection from wind. They are anchored to the house and filled concrete blocks. Attached with ropes.


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RE: High tunnels side by side = how close together?

I wish we could delete our own posts.

This post was edited by myfamilysfarm on Tue, Aug 27, 13 at 12:37


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RE: High tunnels side by side = how close together?

Sorry, what I was referring to as baseboards are the 4x4's (?) with holes drilled in them that the pipes are pounded down through into the ground, then the hoops are pinned into the flared ends sticking up above the wood. Though I am still thinking of ways I could raise the sides a little (2-3ft) to give a little more room for crops right at the very sides though I don't need more than 7ft in the center.


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RE: High tunnels side by side = how close together?

Can you just use a longer piece of pipe for the ground stake? You can stabilize the tops with a 2x4 hip board running parallel to the ground, 3 or 4 feet up. Conduit straps make it easy to attach the board to the hoop. And you may want more height at the center. I have Clearspan's 14ft wide quonset, and it's 8 ft high at the center. Rain water will collect by the hip boards if the angle is not steep enough.


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RE: High tunnels side by side = how close together?

What I've got is 90 18"-20" or so pipes (chain link top rail I think) with belled tops, those were pounded through the holes drilled 3ft apart into the 4x4 PT timbers to make the original 135ft long tunnel. So if I am doing shorter tunnel(s) then I will have extra, but I have to find a source if I want to use longer since local HD doesn't carry chain link (smallest HD in the state).

I was wondering if every single pipe (groundstake?) had to be sunk 14-16" into the ground, or if we could just maybe sink every other one? The western edge, and the northern end, of the pad weren't built up with much topsoil originally, so I don't know how close the solid ledge is to the surface. But I probably will have to buy longer pipe (and/or anchor that end with cinder blocks, etc.) for the southeastern corner since that was built up more with the topsoil that my uncle was pushing from the north - land slopes to the south and east. So that's got probably a foot of loose dirt right in that corner.

I have to hunt for the thread from last year about sinking posts in, how tall/deep and how far apart, I remember Jay saying ground stakes weren't enough (though they were for Uncle Harry, he didn't leave his plastic up all winter either but they did withstand hurricane season, of course he had ground stakes every 3ft).


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RE: High tunnels side by side = how close together?

Ours don't go thru 4x4's, but just into the ground, then attached to 2x6s (I think). Each one is pounded down to about the same depth. One shorter one might be the weak link to take the entire house down.

Hurricane season isn't too bad, starts at 74 for category 1 and goes up. We get winds like that. The worse thing about hurricanes is the amount of water that moves ALONG with the winds.

My house has been thru equivalent of cat1, and that's probably what your area would normally get.


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RE: High tunnels side by side = how close together?

can you just connect 2 of those 18-20" pipes together to make them longer? you can either use a sleeve or an insert. if you are removing the film for winter then 5' spacing should be fine. if you leave the film on then 4' would be better.


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RE: High tunnels side by side = how close together?

Well, if I want to use the PT then I have to go 3ft or 6ft spacing since they're predrilled. Maybe try 3ft spacing at the ends and middle but in between try 6ft - depends on where I hit rock. Like I said, the north end is going to hit ledge first but that's where we really need to secure - might have to do 48ft house instead of 64ft.

Starting from north - drive the 20" pipe all the way down, then rebar in the center put timber down, slip another 20" pipe over the rebar and drive down a couple inches? Then just drive 2 pipe to top of timber, again rebar, another pipe just slipped over to get the height (hoop has to go into that pipe farther), maybe skip the driving into the ground, just pound the pipe in through the timber barely into the ground? Repeat so anchored everywhere except every 3rd hoop?

So for 64ft long tunnel, starting at north end, anchored at 0, 3,9,12,18,21,27,33,36,42,45,48,54,57,61,64 so 16 points but not all 22? Maybe even skip a few more toward the middle (of course adjusting as we hit rock, but not skipping more than 2 in a row)?

We've been lucky this year (knock on wood), no hurricanes and the 1 tornado missed us, we're inland but past couple of years we have had some strong tropical storms in the summer, but mostly around here we worry about blizzards (lots of snowfall plus high winds). Guess taking the hoops, purlins and hipboards down every year and putting them back up would be too much work though.


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RE: High tunnels side by side = how close together?

i would forget about driving posts through the timbers into the ground and just use the timbers as baseboards attached to the pipes with straps.
attach 2 ground posts together using an insert (another piece of pipe)that can slide into an end of each post and fasten with through bolts. drive so that one is flush with the ground. you now have a 20" deep post and a 20" sidewall. not enough? add more pipe.
i just want to mention that for me growing in the tunnels in winter is the best part of having them. you should build them so that option is open to you.


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RE: High tunnels side by side = how close together?

The holding power of a post in the ground depends on the soil, which is different for everybody. Generally, sandy soils have the least holding power and clay soil the most. I have a clay soil and drive all my posts 24" deep. I use concrete on the corners, and put a piece of rebar through the post at the bottom to make a T so it won't pull out. You can look at Farmtek's web site and see the ground anchors they sell to get ideas.

You are going to want a "driver" for the posts, which is a plug that sits on top for you to hit with a hammer so that you don't damage your post. A 2x4 can be used as an improvised driver, but it's a lot nicer to have one you don't have to hold. Also, I found that when driving chain link posts, if I used a big sledge hammer, my driver would damage the post. But there was no damage when I used a 2-pound mallet-sized hammer.

I think with just about any hoophouse, you need to commit to sweeping off heavy snows as they fall if the plastic is on over the winter. I got lucky with my clearspan building; it held what I think was about a thousand pounds of snow over its 14x48 area. I don't think the high tunnel I just built out of top rail would take that much snow without collapsing.

This post was edited by Cole_Robbie on Mon, Aug 26, 13 at 21:27


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