My green/hoop-house thingy build

I didn't have a garden last year as we prepared to move, and this year I need to build a new garden structure. The structure has three main purposes:
1. Provide a place to grow food.
2. Provide protection from the other forest inhabitants
3. Extend the growing season somewhat.

I have done a bunch of reading and video watching on various greenhouses and hoophouses, raised beds, and other systems. I am building a combination raised bed hoophouse where the hoop is supported on top of tall, raised beds.
Here is phase one where I set the base for the building out of pressure treated 4x4s on a built-up earthen pad and a couple inches of gravel.
The pad is behind our workshop. It gets fairly good sun exposure through the day, with a couple of tall pines providing shade during different times during the day. Maybe not the ideal location, but it was the only spot approved by the Corporate Office.
It took quite a lot of dirt to raise one end to match the other as there was about 18-inches of elevation difference in 20 feet.



The structure will measure 20ft x 10 feet under the hoop, and the design requires the base be slightly over-sized. The 4x4s making the base are notched and joined.





The base laid on the pad and squared. The pad was still about 3-inches out of level from one end to the other. So, leveling the base was not an option. Using strings and a laser level, I leveled the two short ends from corner to corner and flat planed the base from one short side to the other.



The notched corners look like this and will be screwed together with 4 screws 3-inches long. The long sides have a similar joint to achieve the 20-feet of length required, but that joint has a 6-inch overlap and six screws holding it together.



To keep the base from shifting during construction and provide some lateral stability in use, I forged points on some 18-inch rebar stakes, drilled holes through the 4x4 base pieces and anchored the base.





Today I hope to start building the short frame walls that will become the hoop supports and the backs of the raised beds.

Phase two of the build: Framing the walls.

I will start with the longer walls. These are 20 feet long and 3 feet tall. The hoop roof structure will rest on top of these walls. That will put the apex of the hoop at about 8 ft-4 inches above the walking surface.
I laid out the plates and cut studs. The walls are framed resting on the base and some 4x4 cut-offs. These will become the back walls of the garden beds.



After squaring the wall and tacking the corners down to keep it square, I started nailing some OSB sheathing to what will be the inside of the wall. I am letting the OSB overhang the bottom of the wall enough to cover the 4x4 base. This allows me to do two things:
1. Nail the OSB to the base to keep the wall plumb and connected to the base.
2. separate the pressure treated base lumber from the soil in the bed.



The OBS needs to be notched out where the wall rests on the short wall base.



With the wall fully sheathed, I can apply the waterproofing. This is a peel & stick membrane used in roofing applications. It came in a 1000 ft roll. I rolled out enough to cover the wall, cut it to length, and rolled the cut piece up again to start adhering it to the OSB.



With the waterproofing fully adhered, I trimmed off the excess and the wall is now ready to nail down to the base.



The other long wall is next. The shorter walls will be done once the two long walls are in place. The old guy is not as fast as he used to be, and the weather is not exactly cooperating either. So, it may be a few days before I can get back to this project.
In the meantime, I may have to do some forge therapy and start making a few knives for commissions.

I really do need to get this thing built. Some of my indoor bean starts already have blossoms on them. Note to self: start indoor planting later next year.

Some minor progress.
All four walls have been waterproofed and stood up. They are nailed to the base and to each other. Everything is plumb and squared.
The front view where the door will be.



The view down the side. The total length is 20 feet.



The water proofing only goes 30 inches out from the corner on the short walls. This will be the width of the beds. The boards that make the sides of the beds with inset into the end walls.
So, I wrapped the waterproofing around the stud at this point. The bed boards will nail over the wrapped waterproofing.





I also covered and sealed the inside corners where the walls meet.



Next up is building the beds. We have to go into town tomorrow and this will wait until Wednesday.

Today I laid out the bed lines and set the 4x4 post bases. The 4x4 posts will serve two functions:
1. They will support the roof beams and 2. they will provide a center attachment/support for the bed walls.
The beds are 27 inches tall (68,6 cm). This will be accomplished by stacking (2) 2x12 boards and (1) 2x6 board. The first board will be a 2x12 and it needs to be notched to fit around the base and inset into the wall.



Pro tip: When you are building anything from the ground up, stringline is important to have on hand.
Here I stretched a tight string from one end wall to the other where the inside, top edge of the bottom board will be.



This allows me to set the post base at the seam and get it almost exactly where I need that post. These post bases: https://www.homedepot.com/p/LTL-Home-Products-Groundmaster-30-in-Gray-Post-GM-30/100039044
You just hammer them in with a big sledge and pray to the Gods of your choice they go in straight and plumb. If they don't, (mine didn't), you will need to notch the 4x4 post to get a precise fit. (more on that later)
Use a cutoff of a 4x4 inside the base to hammer on.



I got both post bases set this afternoon as I spent the morning finishing up a sheath for a knife I recently made and forging some kitchen knives for commissions.



The bed boards will be moved out of the way to set the posts and the roof beams. I can always come back and reset the stringlines to finish building the beds.

I told you I would show you how to correct that twisted post base and here it is.
Set the post in the base and brace it off plumb in both directions.



Measure the distance from the bed boards on both corners. These will be different measurements. One corner was 1/2' off the board, the other corner was 7/8" off the board.
Mark the top edge of the post base on the post.



Take the post out and draw the lines around to identify what needs to be removed.



Time to break out the hand saw. The top cut that is the top of the post base is a straight line, but it is a deeper cut at one end than the other.
The slice up the post is at an angle across the bottom of the post.



Clean up with chisels.



Insert the post back in the base and brace it plumb again. Checking the fit.



The post supports the center of the beam run. The ends of the beams are supported on wing-walls framed alongside the door and window framing. I have run stringlines from the top of one wing-wall to the other.



With the post braced and set in the base, the strings show the lines to cut the steps for the beam.





Shim the post in the base and tighten the bolts



Set the beams on the wing-walls and the post and nail them in place.





Repeat for the other beam on this side. Move to the other side post and repeat.

We got all three beams set, put the center one up this afternoon. It is (2) 2x8 boards 20 feet long.



It needs some additional support at the halfway point to keep it straight and take some weight off the beam, so I added a couple of 4x4 braces down to the two posts.



Now to start the beds. I am using a scorch and oil technique to waterproof the boards. I'm not charring the wood. It's a light scorching to open the grain and provide a tough "skin".



That's a roofing torch, but you can also use a weed burner or similar propane fired torch.
I also do the ends and edges.



Then I apply a liberal coating of boiled linseed oil.



When finished, you let them dry, and the oil will harden.



I may do the outsides of the beds as well. I use this technique on some softwoods for knife handles. I really like the look of it, and it holds up really well over time.

Joshua -

I didn't comment earlier, but I am watching your build with keen interest.

Though I probably won't do exactly what you have done, I do need to put up some sort of season stretcher over some existing raised beds.  And soon-ish.  We have starts that are blossoming (pinched off, so far, but they need to go in the ground, and we still had a hard frost this AM - nominal frost free date is June 1, here).

Anyway, thanks for documenting your build.

Kevin

Kevin Olson wrote:Joshua -

I didn't comment earlier, but I am watching your build with keen interest.

Though I probably won't do exactly what you have done, I do need to put up some sort of season stretcher over some existing raised beds.  And soon-ish.  We have starts that are blossoming (pinched off, so far, but they need to go in the ground, and we still had a hard frost this AM - nominal frost free date is June 1, here).

Anyway, thanks for documenting your build.

Kevin

I'm happy that you are finding it at least somewhat useful. I'll give a little preview of what's to come so maybe you can add the ideas to your own build.

The "hoops" will go from the top of one side wall, up and over the beams, and down to the other side wall. The "hoops" will be made from these cattle fence panels: https://www.tractorsupply.com/tsc/product/feedlot-panel-cattle-16-ft-l-x-50-in-h
They also make some that are 8 ft long. The 16-ft length makes for a semi-circle with a 10-ft diameter.  These will get stapled down to the tops of the walls and each beam. The hoops will be covered with 8-mil greenhouse film from Bootstrap Farmer. The width of the green/hoop house is 10 ft-7 inches from outside edge of wall to outside edge of wall. This brings the panels down about 2-1/2 inches from the outside wall edge. This allows me to secure the film to the top of the wall with a standard 2x3 furring strip.

Once I get the beds built, I can start filling them and close in the inside lower portions of the end walls.  Once I get the hoops in place, I can frame in the upper end walls, set the door, and frame in the window vent.

It's really interesting to track your progress. Excited to see the end result once it's finished

Bed building day.
I set up the stringlines for the first row of boards, cleared away some gravel to get the top edge on the line, and set the boards.



The bottom at the post will get drilled straight through the post base and screwed to the post. (2-1/2" coated deck screws)



The 10 ft span may be a little much considering how deep these beds will be, so I am setting a midway support. This is a 2x12 cut to fit between the bed board and the back wall. The bed boards get screwed to the support and the support gets screwed to a 2x4 in the back wall. This is non-structural. It just needs to spread out the force and keep the screw from being pulled through the OSB sheathing.



The second row of bed boards is a 2x6. The second row of center supports is another 2x12. These will be totally below the soil line.



The third row of bed boards is another 2x12. All three rows get screwed to the end wall with 2-1/2" screws.



The edges of the bed boards get a bead os silicone caulk as do all the interior seams where the boards attach to the end wall.
The first bed done.



Both beds done. The tops of the center supports are about 5-1/2 inches below the top of the bed. That should give enough soil cover for planting. The roots can find their way around the support.



The backstop 2x4 behind the center supports. I used 3-inch screws to attach the supports here.



We are taking Liz's artwork to a show in Flagstaff, so it will be a couple of days before I get back to this.

It's been a while I know, but things have been going at the pace of the Crusades.
Filling these beds has been a lot of work. First thing to do was put in a layer of dead and half-rotten wood. I just happen to have several piles of that lying about.



After putting a layer of that in the bottom, I filled the voids between the logs/chunks with wood chips and other organic debris.



This got a healthy serving of compost starter, a little water, and let set overnight. This compost starter: https://www.tractorsupply.com/tsc/product/espoma-organic-compost-starter-cs4
Then, another layer of dead wood, covered with leaf mulch, biochar, pine needles, twigs and whatever else I could shovel up and throw over it. Another helping of compost starter sprinkled over that.



Then I took large pieces of pine bark and put them in the cement mixer with a couple of big rocks to make hand-sized chunks. A layer of about 3 inches over the top



Now I will start layering the soil to get somewhere around 10-12 inches of soil. This will be a mixture of the local sandy/clay with some good, composted soil I moved from my garden in AZ.
Currently, I have almost half the beds done to this point. Tomorrow, I can finish the pine bark chunks and start closing in the end walls.

I also got the fence panels placed for the roof structure.
The first panel went up and it did not want to make the semi-circle I had planned. It was about 6 inches above the top beam.



So, I got to thinking (dangerous business) that I kind of preferred the gothic arch rather than a semi-circle for snow shedding purposes.
This meant raising the center beam about 7 inches and stacking a 2x4 on the other two beams.



The panels are stapled to the tops of the sidewalls, and stapled to the beams. If I had just been about 2 inches taller, I could have reached over the edge of each panel. I had to put in a couple of staples for each panel from below by reaching up through the panel and hammering downward.
Yes, it was as uncomfortable as it sounds.



The whole roof structure is quite rigid. There is almost zero movement to cause rubbing and tearing of the greenhouse film (when I get around to installing it).