high tunnel plans

[pecker88]

I decided to go with Johnnyseed's Gothic Arch Bender. I drafted a "wall section" plan and will be applying for building permit tomorrow. According to city building and zoning folks, I'm cleared for a greenhouse on my lot as long as it for personal, not commercial use. I'm going to be ★★★★ed if there is a snafu in getting the permit, I just placed a Johnnyseeds order!

32' Long X 14' Wide X ~9.5' Tall at center
double layer clear 6 mil poly film. Johnnyseeds spacer blocks between layers
Roll-up sides
End walls will be identical; treated 2x4, covered with clear rigid roofing panel (home depot)
I'll get used storm doors on craigslist

[Cole_Robbie]

Neat. That's exciting.

For what it's worth, you really only need concrete on the corner posts, unless your soil is very sandy with no clay. 2x4s should be fine for the hip boards, instead of 2x6s. And for the plastic below the hip board, you want a single layer, because you can't inflate the part that rolls up, at least as far as I know. I doubled the plastic in that section and mine turned cloudy from rubbing together. A single layer would have been better.

Your two end purlins take the brunt of the wind. When a greenhouse collapses from wind, the end purlins twist, and then it all falls in. If you want to strengthen your structure, extra bracing for the each end rafter is the first place to start.

[pecker88]

Originally Posted by Cole_Robbie

Neat. That's exciting.

For what it's worth, you really only need concrete on the corner posts, unless your soil is very sandy with no clay. 2x4s should be fine for the hip boards, instead of 2x6s. And for the plastic below the hip board, you want a single layer, because you can't inflate the part that rolls up, at least as far as I know. I doubled the plastic in that section and mine turned cloudy from rubbing together. A single layer would have been better.

Your two end purlins take the brunt of the wind. When a greenhouse collapses from wind, the end purlins twist, and then it all falls in. If you want to strengthen your structure, extra bracing for the each end rafter is the first place to start.

my soil is 100% gumbo heavy clay. I think I'll take your advice and only concrete the corner posts. Still 8" of snow on the ground, so I have some time to think...like I need to do more of that!

[Ricky Shaw]

That's a beauty!

[Worth1]

Another thing I would like to add.
If you are going to sink pipe up into concrete footings make sure the concrete is above grade.
Also it will last almost forever if you wrap it in underground pipe wrap.
I would much rather use anchor plates on the bottom of the metal and bolt it to the concrete.
Do this by putting your J bolts in the concrete before it sets up.
Make a plywood pattern just exactly like the pattern of the support plate put your bolts and nuts one it and set it in the concrete so it doesn't move around or sink.

Worth

[pecker88]

Originally Posted by Worth1

Another thing I would like to add.
If you are going to sink pipe up into concrete footings make sure the concrete is above grade.
Also it will last almost forever if you wrap it in underground pipe wrap.
I would much rather use anchor plates on the bottom of the metal and bolt it to the concrete.
Do this by putting your J bolts in the concrete before it sets up.
Make a plywood pattern just exactly like the pattern of the support plate put your bolts and nuts one it and set it in the concrete so it doesn't move around or sink.

Worth

everything I've read says to have the top of the concrete slightly below grade when setting chain link fence posts; prevents frost heaving. In the above drawing, the concrete footer is 4" below grade. I will also put bolts through the posts prior to setting them in concrete to prevent them from pulling up after the concrete sets.

[PureHarvest]

What do you figure you'll have in it, not counting your raised beds as they are already built? If you don't mind me asking?

[Worth1]

Originally Posted by pecker88

everything I've read says to have the top of the concrete slightly below grade when setting chain link fence posts; prevents frost heaving. In the above drawing, the concrete footer is 4" below grade. I will also put bolts through the posts prior to setting them in concrete to prevent them from pulling up after the concrete sets.

I was thinking more on the lines of a catastrophic event such as the collapse of the structure.
This way you could start over without having a bunch of pipe or what ever stuck in concrete you couldn't do anything with.

To prevent frost heave pour the footings down below the frost line.
Worth

[Worth1]

You should try to build something on permafrost and see the mistakes people make.
The building heats up the permafrost and the whole thing sinks in the ground.

Worth

[pecker88]

Originally Posted by PureHarvest

What do you figure you'll have in it, not counting your raised beds as they are already built? If you don't mind me asking?

don't mind at all. My goal is to build a middle-of-the-line hoop house, not cheap, not elaborate.

I'm doubling my current raised bed area so I have roughly 1/2 the soil I need. The city gives away free compost in the spring, I'll go get a few pickup loads. I just found out about this program yesterday, seems too good to be true: see here

The above order from johnnyseeds was $812.85 including shipping. I'm waiting on the rest of the material until spring, and so my wife doesn't loose her cool.

Items remaining:
treated lumber for hip/base boards and end walls - $200
clear poly roofing panels for end walls - $80
hor/vert enclosure strips for corrugated roofing panels - $20
hardware - $50
storm doors - $50
double 6 mil poly covering, 40x75 ft - $380
10ft chainlink top rail - $350
8ft chainlink line posts - $150
chainlink fasteners misc. - $40
quality landscape fabric for under/around line posts - $125
parachute cord for lacing roll-up sides - $40

sub total: $1485
grand total: $2298

seems reasonable for a cathedral shape 32x14 structure with double poly, no blower.

[pecker88]

Originally Posted by Worth1

I was thinking more on the lines of a catastrophic event such as the collapse of the structure.
This way you could start over without having a bunch of pipe or what ever stuck in concrete you couldn't do anything with.

To prevent frost heave pour the footings down below the frost line.
Worth

I've thought about this, more-so when I was thinking about using 4x4 treated posts, (see earlier posts in this thread) as they would be easy to swap out when they rotted.

But several building forums mentioned that above-grade footers with anchors like you explained are for downward point loads, (houses, decks) and not so much for fences. The physics in my head seemed to justify their claim, but I'm by no means an expert.

[Worth1]

Originally Posted by pecker88

I've thought about this, more-so when I was thinking about using 4x4 treated posts, (see earlier posts in this thread) as they would be easy to swap out when they rotted.

But several building forums mentioned that above-grade footers with anchors like you explained are for downward point loads, (houses, decks) and not so much for fences. The physics in my head seemed to justify their claim, but I'm by no means an expert.

Here is the deal about footers for net and chain link fences you want to have them below ground for three reasons.
One the bottom of the fence is at ground level.
Two you dont see the ugly footers sticking up.
Three the soil wont wash away and leave the footing sticking above ground.
We dont have frost heave here where I live in Texas but we do have something else and that is in many places clay soil.
No one builds a house on clay soil here that is worth a hoot.
They may pour footers and the slab but they dont drop pilings below the line in the clay where it doesn't get dry and wet.
Now everyone has a house that moves around.
One way to stop this is to put in rain gutters and channel the water away that is what I did.
Another thing to do is to excavate out around the area of the house and put a layer of stabilized sand down on top of the clay before you pour the slab.
That slab needs to be on a vapor barrier.

Worth

[Cole_Robbie]

Your roll-up sides will need something to roll around if you want them to roll neatly, typically top-rail. For my high tunnel, I just pull up the sides and clamp or bungie them to hold them up. It doesn't look as neat, but it works.

This stuff is great for attaching plastic to lumber for the end walls and doors:
http://growerssolution.com/PROD/batten-tape/BTFS

[Worth1]

Originally Posted by Cole_Robbie

Your roll-up sides will need something to roll around if you want them to roll neatly, typically top-rail. For my high tunnel, I just pull up the sides and clamp or bungie them to hold them up. It doesn't look as neat, but it works.

This stuff is great for attaching plastic to lumber for the end walls and doors:
http://growerssolution.com/PROD/batten-tape/BTFS

Is it sticky too.
Were I put the soil back to where it belonged next to the house is where I want to put a shed green house made out of wood with a wood floor like a deck.

Worth

[pecker88]

Originally Posted by Cole_Robbie

Your roll-up sides will need something to roll around if you want them to roll neatly, typically top-rail. For my high tunnel, I just pull up the sides and clamp or bungie them to hold them up. It doesn't look as neat, but it works.

This stuff is great for attaching plastic to lumber for the end walls and doors:
http://growerssolution.com/PROD/batten-tape/BTFS

ugh, I forgot something else on my above list...
10ft sections of 3/4 EMT + fittings - $60

I'm following JS's guide, almost exactly; they said to construct roll-ups with 3/4" EMT. I ordered a bunch of poly-channel & wire from JS's; that's how I'll attach poly to side walls.

For end-walls I'm going to build a 2x4 frame that roughly follows the arch, then attach the poly-channel to the 2x4's. The poly film gets ran over the end of the end-wall arch, and straight down to the poly-channel. Just below the poly-channel on the 2x4 I'll fasten the rigid clear roofing panels. Seems like a good way to "union" poly film and rigid poly roofing panels.

Example pic: note the poly-channel running along the 2x4 under the arch. Same idea.