Tuesday, August 23, 2011

Garden Construction Project: Building a Hoop House PART 1

Awhile back, I mentioned we were getting ready for some winter gardening...ta DA...I can finally reveal how we will do that! We are building a hoop house!!! We have slowly been working on it over the spring and summer. I am super excited about it!

A hoop house (also called a high tunnel or poly tunnel) is a passively heated structure--from sun radiation alone. It stays just warm enough that you can grow/harvest cold weather crops all winter long. You can extend the season for warm weather crops. (You could heat it on the coldest days, if you needed to.) I can't wait to experiment and see just how much longer we can make the season and what we can overwinter.

It will replace my tent style cold frames, which I cannot find for sale anymore. (I am down to one and it was pretty wobbly this year.) I will be able to start the summer seedlings I started in that in the new hoop house. It will be more convenient than the little cold frames in so many ways, like being able to stand inside it to work!

Our hoop house is about 14' wide x 28' long and nearly 7' high (at the ridge line) and the Quonset style. The 1:2 ratio is supposed to be ideal for retaining warmth. The ribs and ridgepole are made from chain link fence top rails and line posts and the ends are framed in lumber. The plastic covering is greenhouse suited (UV protected) 6 mil held in place with wiggle wire.

We used the "Quick Hoops" method of building which involved buying a special pipe bender, ground post driver and some specialized cross-connectors.

The first part of the bend is the easiest to make.

It gets harder toward the end and Jeff put all his weight into it!

It seemed so straightforward...however, there was a hiccup. Our hoops ended up being wider from end to end than the suggested 13' to 15' for the 12' wide house that we had instructions for that came with the bender. They were mostly around 16' 5". You do need it to have some outward tension for stability, but this was too hard to compress to size and caused the top of the arch to bend at the connection point. Jeff called customer service at Johnny's Seeds and they said other people were getting similar widths, or even larger. It seems to depend on the lot of metal you get. Anyway, we were told we could try to force it to fit as long as someone was holding down on the middle of the arch at the same time to keep it from bending sharply at the stress point, or just drive the ground posts a little further apart and make a slightly wider hoop house. The middle still bent under the strain, so we experimented with width and settled on 14'. We couldn't insert the hoops as far into the ground posts as indicated in the instructions. We went with what the curve would allow, which was 5 inches. It still required Jeff to swing like a monkey from the bars, wrestling them into place! And, a little WD-40 on the pipe ends helped too.

This picture shows the line posts getting cut in half to make the ground posts for the hoops. A saws all made short work of it.

It was exciting to drive the first post and have construction really underway! Despite having so much slate in the ground here, it was pretty easy to drive posts. Only one was a bother and that's because we hit some hard fill that we speculate must have been under one of the sheds that used to be here. We'd previously dug out some large slates from the same area that may have been under the sills, but who knows!

Fortunately, our site is nearly level with only about 2.5" of variation. This shot shows most of the posts in place.

With all the posts other than the problem one driven in, Jeff started working on the hoops again. He connected the two pieces that form a hoop, drilled a hole at the ridge line and used a hex bolt to fasten them together. At this point, with the wider, less bent hoops, he put them back in the bender and put a little more bend in the ridge line area. This trick really helped a lot!

Here is a progress picture showing just one more hoop remaining and the problem ground post in the left foreground. We ended up having to use a little concrete in that one.

Jeff drilled holes through the ground post, hoop and baseboard for the carriage bolts.

We used tie plates to connect the sections of baseboard (same for the hip board too).

Here is the end wall framing in progress. There weren't directions for end walls, so we just improvised.

Here is a detail of the cross connectors that hold the ridgepole and the galvanized strapping we used to secure the end wall to the hoop.

Here is the siding in progress. We clamped the sheets in place and Jeff traced the shape of the arch onto them and then he cut along the line with the jigsaw.

The siding was screwed to the frame.

This picture shows the siding in progress with the corner bits still to do.

At last all the wall pieces were in place!

And, it was time to stain the exterior. We chose a color called "Cape Cod Gray" which we are very pleased with.

Soon, I will do a "Part 2" post showing the doors, hip board, wiggle wire tracks, roll up ventilation for the south side and the 'skinning'. Well, it may be more than one post...we'll have to see!

I have a lot of learning to do, but my hope is to have fresh greens for Christmas dinner this year. I expect it will take me a few seasons to really get the hang of it though--especially with a baby keeping me busy!

Something else I'm looking forward to is having a chair in the hoop house and on a winter day, going out there, taking off my coat, hanging it on a hook and sitting in the sun and warmth, semi-outside. I can totally picture myself having my coffee there! Of course, I'll probably see all the work that needs doing and not do much sitting around, after all. That's what usually happens when I try to go sit by the summer garden!

Part 2

Part 3

all hoop house posts


2paw said...

I had no idea what a hoop house would be. I was imagining hula!! Jeff is a great builder and I can picture you having coffee there too!!

Kristen said...

Wow, what a project! I couldn't even get anyone to rototill the (non-existent) garden this year. You will really enjoy year-long gardening now.

Thomas said...

Sarah, it looks AWESOME!!!!! I can't wait to see how it turns out. You guys have come up with a great design. I'm so excited for you.

Anonymous said...

Looking for a little guidance for the greenhouse that I'm building this fall. How long are the cahin link fence rails? And where do you buy them?
Good luck with your project. I built a PVC hoophouse 5 years ago and it has proved invaluable.