Greenhouse Walls Inner Forms

Will bracing the first inner wall forms.

In our quest for better winter farrowing we are building a combination greenhouse winter farrowing space. The greenhouse design is the cumulation and analysis of the last several years of experimentation we’ve done with a wide variety of temporary winter shelters for our livestock, in particular the pigs. This has ranged from pallet sheds to earthsheltered dens to wire ribbed greenhouses to haybale homes to pole sheds to the solar glazed south end shed. A common thread through all of them is that they are open to the outdoors so that the animals get plenty of fresh air. Even in our cold winters, the temperature is not the issue as much as having fresh air, dry bedding and protection from the wind.

Greenhouse Layout – 1 grid square = 1 foot

A couple of weeks ago we poured the greenhouse footers which then got stripped of their forms to reveal their strength and beauty. As the concrete cures to full strength we’ve been working on making the outer wall forms, raising the flume, installing the steel reinforcing and now the inner wall forms as we get ready to pour the kneewalls of the greenhouse. The greenhouse lower walls are made of steel reinforced concrete because pigs can be very hard on structures. Between their manure, back scratching and teeth they destroy wood in short order. Stone is my favorite solution but concrete is faster and even stronger as a whole. Additionally, the greenhouse is built into the hillside to give it a lower wind profile which will keep it warmer in the winter.

Note that the tractor can drive into the greenhouse to clean out bedding at the end of the year and deliver large round bales of hay. Over the course of the winter we let bedding hay build up to provide a deep bedding pack that helps to keep the pigs warm through the winter. The bedding begins to compost which generates considerable heat – warm toes! That compost is then a valuable resource for our gardens, orchards and fields.

Rail Groove Form Goal

The foundation of the greenhouse is 66’6″ long by 28’3″ wide and open on the south east side to catch the morning sun. Inside there will be 12 pillars to break up the roof spans into 8′ and 12′ long sections making the structure easier to build and stronger. These 8’x12′ also happen to be just the right size for winter farrowing nurseries. During the summer sows go off into the margins of the pasture to build a nest and get away from the herd when they farrow a new litter of piglets. About a week later they return with piglets in tow but for a while still keep to themselves. Unfortunately, in the winter these periods of isolation are much harder to achieve. Our solution to this has been to setup nurseries for the sows where they can be off by themselves or with one or two other sows that are farrowing at the same time in the winter. Up until now all these spaces have been of a rather temporary nature, changing from year to year using our various summer garden spaces. Getting the sows to those areas from their winter herd space can be tricky. The greenhouse with it’s easily reconfigurable sub-spaces will make that much easier.

Rail Groove Form Space in Inner Wall Forms

An essential component to this goal of easily reconfigurable spaces is that the interior of the greenhouse. Built into the wall and the 12 pillars we will have slots that can take rail dividers such that each of the 12’x8′ spaces can be sectioned off to create individual stalls. This way we can have a ring of stalls around the perimeter on the south, west and north sides with a central open area for the herd. Or perhaps we’ll find it works best with three lines of three farrowing nurseries and two open herd areas. The key is the interior is flexible and can be reconfigured in a day so that as our needs change the building can change to suite.

Rail Groove Form in Place

This same division also allows for areas to be set asside for greenhouse plant cultivation areas when we are ready to do that even in the winter. With a glazed roof, which we won’t be doing this year, a set of sub-sections can be easily turned into a green space and it can be heated by the pigs. Not only that, but by having the plants in raised beds the ground floor of the green space can be used as a piglet weaning area.

Rail Groove Mass Producting Jig

To make the rail grooves we needed form pieces that created thicker areas in the concrete walls and then a groove in the middle. In fact we needed a lot of these. When ever making many of something, I consider how I might speed up the process with a jig. The photo above shows the jig for making the Rail Groove Forms. I highlighted the pencil lines on the wood with magenta in Photoshop to make them more visible here. These marks show where to place the various parts and set the screws.

2×4 Parts Placed

Step one in using the jig is to place the long 2×4 that creates the groove in the concrete and the short 2×4 at the bottom that spaces the rail outward from the rest of the wall.

Rail Groove Form Screwed

The plywood is then placed on the 2×4’s using the reference marks on the jig and screwed into place. Most of the screws are 1-1/4″ screws but the one at the top of the form (bottom right of photo) is a longer 2.5″ screw as it will take more force when the forms are removed from the concrete.

Will Foiling the Forms

The photo above shows Rail Groove Forms in their pre- and post-foiled forms. Will is using a 2×4 jig to cut strips of Foil-Bubble-Bubble-Foil to tack onto the long vertical groove 2×4. If we just used a 2×4 to make the groove the resulting slot would be too thin to easily get rails in and out of. By wrapping the form in foil it thickens the form a little thus widening the resulting groove in the concrete walls and pillars by 1/2″.

Installed Rail Groove Form

This Rail Groove Form is in the south east corner of the foundation as it curles around in a serif to provide extra buttressing at that point. The extra thickening done every 8′ and 12′ around the perimeter wall also serves to strengthen the wall by adding buttresses.

Holly notching braces and rail groove 2×4’s for header long brace.

Notched Braces and Rail Groove Boards

The cross braces that join the two walls will be removed as we fill the final bit of concrete into the forms in order to get a smooth top to the wall.

Header Brace in Place

The purpose of the header brace is three fold: 1) it locks all of the form pieces together; 2) it straightens the wall; 3) it widens the wall for the top 1.5″ inches creating an I-beam and thus a much stronger wall while using less concrete than if we had made the entire wall that thickeness.

Walter Holding Spacer Block While Will Screws Header Braces Down.

Again, a simple little jig makes the process go faster. No need to use a measuring tape over and over.

Jeffries 2008

We signed and dated the greenhouse by writing on one of the inner wall forms using silicon sealant. The bead of silicon hardened and now when the concrete goes into the form it will act as a mold. When we peel the form we’ll have the year and our name imprinted in the wall.

Outdoors: 50°F/26°F Cloudy, Miniscule rain in morning
Farm House: 65°F/53°F 2 round bales out N & S
Tiny Cottage: 65°F/55°F

About Walter Jeffries

Tinker, Tailor...
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8 Responses to Greenhouse Walls Inner Forms

  1. Beaker says:

    Wow, your idea for your signature molded into the wall is genius. My husband and I will be laying a new walkway for our house soon. Maybe I will steal your idea to so something artsy :)

  2. Lellie says:

    Hi Walter,

    It’s a very good description and explanation of all the aspects of building your green house. I am impressed with your design – the built in groove – the tractor arrangement – and to top it off your signature.

    And then I thought about the wonderful art work Holly does and wondered if she was going to immortalize your face in the concrete, too. (Grin)

    I read your blog faithfully, as I pine for my own farm while being married to a confirmed cityboy.


  3. Beaker,

    Check out this post:

    Master Bedroom Inlayed Ceiling

    That article describes how I inlayed chips of polished granite and stones into the underside of the ceiling of our bedroom. You could do something very similar in your walkway. Fun and elegant!



  4. Alex Tiller says:

    Looks like quite the project. Thanks for all the interesting pictures.


  5. Jeff Marchand says:


    I love the concept. Can you post an update on the greenhouse/pighouse? I ‘d love to see some pictures of in in action with both pigs and plants etc.

    • Jeff, these two photos [1, 2] will give you an idea of where the ‘greenhouse’ is at this point. At the time I designed the greenhouse we were still under the assumption that we would not be even starting to think about building our own butcher shop until 2014. At that time advancing our winter animal housing was our priority.

      Then in April of 2008 our butcher announced he wanted to give it up and tried to sell his place to us. We weren’t interested as we didn’t want his headaches and he is an hour from our farm – it is bad enough driving the long trip once or twice a week, I would not want to manage his employees. Thus began our saga of our Big Project which has used up almost all of our money and a great deal of our time. We’re making excellent progress on the butcher shop however until that is done we won’t have the cash to put up the proper glazing I want to do on the greenhouse. I don’t want to do the thin plastic poly – we get high winds which will rip a large poly sheeting greenhouse apart. Instead I want to use polycarbonate or fiberglass glazing. We have done this on the house end shed and other places with great results.

      With the switch in plans I spent all the money we had planned for the greenhouse on doing what we’ve done so far on the butcher shop. For a few years the ‘greenhouse’ will consist of a court yard ringed by sheds who’s roofs are made in a great part from the materials we recycled from the old hay shed we took down to build the butcher shop. The pigs are enjoying those sheds in the worst weather of winter although generally they prefer sleeping out under the stars. As we built the butcher shop, our Big Project right now, there are many small side projects like the west shed we’re working on putting up in the ‘greenhouse’ and a little weaner greenhouse. We are going to make a small temporary (3 to 5 year?) version of the greenhouse that is only about 12’x20′ in the central part of that area for this winter’s weaners and are hoping to use the upper air space in there for plants so more details to come next spring.

      As to interaction with the pigs and plants, for the most part they don’t and won’t in the greenhouse. Weaners and sucklings will be down on the ground and plants will be up in growing beds. The pigs will provide heat and CO2 to the plants although I don’t know how much the CO2 will vary from outside since there will be air exchange. To be seen.

      One other detail, the rail grooves I designed into the concrete worked really well. They make it super easy to divide the space up into a variety of configurations. We have used this now in several arrangements and are very pleased. Improvements would be to make the rail grooves go all the way to the top and bottom of the pillars but other than that they’re perfect.

  6. Cleve says:

    Hello Walter,

    My name is Cleve and I’m headed where you’ve already traveled, so-to-speak.

    First, let me say I really enjoy reading your blog. Very informative and detailed.

    Second, I’m somewhat perplexed and would love to understand your thought process here…

    …I’m fairly certain I read on more than one occasion that you are a big proponent of NOT keeping livestock in barns (bad for animals, bad for humans, extra work that shouldn’t need to be done). I noticed that you attempted multiple variations of a farrowing shelter, even going to your portable option so that you wouldn’t have to move a sow after she’s “nested”.

    I’m curious how a fixed structure, such as this combination greenhouse/ farrowing “barn” fits in with your (previous) philosophy…or is it as simple as you changed your mind?!?

    Curious in California,

    • Good question. No change in midn. If you look at what we’ve used from greenhouses to dens to hoops to huts over the years you’ll see this has a lot of similarities and brings together a lot of those elements. This is not a closed in barn. It is an open space. What I still don’t like about traditional barns are a whole slew of things including but are not limited to:

      -Poor ventilation which results in:
      -Respiratory disease for the animals
      -Respiratory disease for the farmer
      -Too warm in the winter which causes moisture problems that cause:
      -Structural problems in wood and metal barns as they rot
      -Rodent problems
      -Fundamental structural issues dealing with snow load of most barn roof designs
      -Mucking out stalls
      -Inflexibility of the structure to adjust with changing needs
      -Abuse of the structure by the animals
      -High maintenance costs
      -High cost of construction
      -High tax burden due to over zealous greedy governments

      The greenhouse, or south field shed as we tend to call it since it doesn’t have it’s greenhouse top yet, has none of these issues. The south field shed is very open to the weather. It gives shelter but it does not restrict the flow of air such that it would cause the build of moisture or ammonia gasses that could cause health issues. I let the bedding build up to be a deep pack which composts in place creating a warm bed. The animals have only used it in the winter weather. During the summer it gets to air out and dry.

      In addition to the south field shed we have other smaller structures we’re experimenting with. This has been a continuous process over the past decades of figuring out what we like for animal housing for various animals in our climate. (I actually have a big barn and another large similar building but I don’t want to use them for animals.) I’m in the process of designing and possibly manufacturing something that we’ve been experimenting with for several years which will combine a lot of the ideas for pasture housing and farrowing spaces. More news to come on that in the winter or next year.

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