Hoop House: Details of the construction
I’ve been asked to share the details of our hoop house construction in a blog post, so here goes…
After many hours (really weeks) of research, we chose to do business with Grower’s Solution of Tennessee. They actually design, test, and construct their own hoop houses. Their prices (even with shipping) were as competitive as anyone. They also guarantee their covers for four years, which was a major requirement for complying with our EQIP High Tunnel grant terms.
We ordered the framework for the two hoop houses together to save on the motor freight costs. We received 15 bundles and one box containing all the extras, like all the screws we needed (except for the ones to attach the base boards), the connectors, etc.
We personally felt there could have been more clarity and more diagrams in the instructions. We spent a lot of time reading and re-reading to be certain we were correct in our construction.
The site for the hoop houses was an existing garden plot about 40 x 60. The full foot print for the two hoop houses (including a 2 ft walkway) is 44 x 52. We chose to push the footprint as far to the east as possible. We ended up having to offset one hoop house to accommodate a large gate post. That offset is about one foot.
It took us forever to square up the dimensions. This is critical as every thing else is dependent upon the original site lines. A lot of the problems were having the post requiring the offset, having a trench dug parallel to the west site line, making sure we were true north/south.
Keep in mind, we are three women assembling these hoop houses. Our plan is to ask for neighbors to help on tasks that require more muscle than we have, or more height than we have.
We began with the first task…pounding in the ground stakes. These are 1 5/8 inch rolled steel pipes, 30 inches long. The directions say to pound them into the ground leaving 6 inches exposed. To do this, the company sent two bolts w/flat washers (one for each house). The theory is to drop the bolt onto the top end of the ground post and use your sledge to pound. The bolt and washer help to distribute the driving energy across the surface, and minimize post damage.
At this site we have two layers of hard pan. One at about 18 inches and another thicker one at about 24 inches. We had a claw hammer and an old sledge that was heavier than what we could handle. Neither was a good fit for this project. Our local hardware store had a 4 lb Engineer’s Sledge that was “just right”. Sold!
Cindy began lining up each ground post and pounding it in. I joined in, able to at least pound the ground post in about 12 inches or so. She would then follow me making sure the ground post was exactly vertical as she pounded. By keeping these posts exactly vertical, the hoop house ribs line up without many adjustments.
We found that when pounding on the bolt/washer combination, we still flared the top edge, sometimes as much as 1/2 inch or so. We called the company to see what to do, as we thought we’d really screwed up (no solution in the instructions). No problem. The engineer at the company told us that the depth of the ground post is relative, as long as the post was at least 12 inches deep. If the top flared, use a hacksaw or sawsall to cut the post leaving a minimum of 6 inches above the ground. That certainly made things easier.
We had to pound a total of 52 ground posts, so you know how long that took us. We called for help with the last 24 of them.
Once the ground posts were installed and checked, it was time for the bows. These are the vertical ribs of the hoop house. They came in 3 sections. Here you have some options for installation.
The instructions said to lay the three sections on a flat surface, with the taper end of each section going the same way. Slide section #2 tapered end into large end of section #1. Repeat the process with section #3 into #2. Use self tapping screws to secure the ends. Then carry this rib to the site and lift the top, sliding the ends of the posts into each opposing ground post.
We thought about that, and decided three women trying to lift the 1 3/8 diameter ribs into the air wasn’t going to be a pretty sight.
Optionally, we chose to put one section into the ground post. Then lift the next section into the first (kind of Marine flag-raising style). Lastly, we matched the last section with the other two, and dropped the end into the opposing ground post. We saved securing the rib sections with screws to a later time.
Thirteen bows (39 sections) later, we had the skeleton of the hoop house. The second hoop house was delayed because of electric service/water service trenches. Upon the initial observation, the bows weren’t equal. What to do. Again, nothing in the instructions. We figured out that by adjusting each of the out-of-line bows (pulling and pushing etc), we were able to make the hoop house look good.
For the record, how the ribs look (within reason) doesn’t affect the operation in our case as we’re using a double skin and inflation fan. The ribs won’t be visible on the outside.
Next task was to install the center purloin. Again this consisted of several sections of 1 3/8 inch pipe. We followed the directions, screwing each section together before lifting it into place. Well upon doing that, and then measuring, the center purloin was 50 feet but the greenhouse was 52 feet. What to do?
We had several options. We could bend each end in a foot to take up the difference, or we install as much of the purloin as possible, before unscrewing each section. If we only attached the supports loosely, then the purloin would easily slide and we could get enough length, as the connecting tapers were each better than 8 inches long, and there were 5 of them.
With three of us on ladders, and one of us directing, we were able to adjust the purloin, and tighten the supports enough to keep things stabilized. Once that was done, we were done for the day, too. Our shoulders ached from all the overhead work.
A couple of neighbors stopped by and lent us their mini-scaffold which is on wheels. They also dropped off a small compressor and impact driver should we need it. After buying Cindy an early birthday present (cordless impact driver) we felt secure in the knowledge we had plenty of tools to complete the project.
We found that by adding self-tapping screws to EVERY joint, whether a support or primary, we could additionally stabilize the hoop house. We also added additional straps to the base of the bows, attaching two at the junctions of each 2x6x8 and one strap between.
Finally, after a 2 week delay for power and water, one snowstorm, and days on end of wind (a common thing here), we felt ready to tackle the job of putting on the covers. Power was critical for us, as we’re installing double covers with an inflation fan putting air between them constantly. It makes our hoop houses look like half balloons, but it works great for really high wind areas as it eliminates any friction between the ribs and the plastic.
Let’s just say this is a project that needs to be completed when there NO WIND, not even a 5 mph breeze. I’ll write another post about the adventures of installing a hoop house cover in 20 mph wind. I know… we knew better, but it wasn’t blowing when we started.
I’ve taken some detailed pictures showing stabilization efforts, as well as detail of the inflation fans.
We used pressure treated wood for the end bracing to save having to paint. Also, we’ll be “uninstalling the door” before putting on the end cover and the reinstalling with the plastic folded around the wood framing first. That way, the door frame holds the plastic securely.
All joints are either toe nailed or “L” braced for strength. We used drywall screws into the wood, and self-tapping screws into metal.
With water inside, we can hook up our drip irrigation and a ferti-gator system. The electric service is there to support the necessary inflation fans for our double-covers.
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