A homemade greenhouse can be constructed of cheap, local materials that you might not initially consider using, but with a little ingenuity, you can probably make something nice for very little cost – something consistent with your approach to frugal living and self-sufficiency.
I decided that my second “build your own” greenhouse would be made from scratch, and use transmission class power poles readily available to me.
This meant that I could build a greenhouse and save lots of money on materials and labor.
Build your own greenhouse with power poles? Yep, power poles and metal tubing. Let’s take a look to see just how it can be done.
The idea for this second greenhouse was to construct a super raised bed for easy harvesting of vegetables, and then build a greenhouse over the top of it.
It was a good idea on paper, and it also turned out very well.
This example shows that a homemade greenhouse can also be a well-made greenhouse.
Overview
The area I chose was a weedy spot south of high spruce trees that was relatively well protected from the weather and had great southern exposure.
The photo below shows what the raised bed looked like soon after construction began.
As shown in the photo above, the raised bed was constructed out of power poles placed along a sunken walkway to created the inside of this homemade greenhouse.
The outside of the beds were made simply by placing another power pole on a pile of soil approximately equal to the top of the inside poles.
The photo shows tin on the inside portion of the bed that lines the walkway.
The outside poles were being lined with tin at the time of this photo to prevent the soil from coming in contact with the preservative treatment of the power poles.
The same was done to the ends of the bed after they were put in place.
The photo below shows how the project looked after much of the metal tubing was put in place and the wooden ends were constructed.
You can imagine that this homemade greenhouse was a bit tricky to work on.
The raised beds made for a natural pit to fall into as we installed the metal tubing overhead.
Below is a picture of the raised bed after all vents and fans were installed and the poly glazing material was attached.
By the way, when you need a clear cover for your homemade greenhouse, take a look at THOR Tarp.
They specialize in custom made greenhouse covers, shade cloth and wide range of tarps for various applications. And, they’ve been in business for over 12 years.
With lots of different materials and options to choose from, I’m sure they can help with your greenhouse project (and many other kinds of projects).
With our high winds, hail, and risk of heavy spring snows, I’m very cautious, so I overbuild my homemade greenhouse structures and use woven poly for the covering.
Northern Greenhouse Sales provided both the clear woven poly for the external cover and the super heavy duty white woven poly used to cover the telephone pole foundation on either side of the sunken walkway.
Bob and Margaret Davis are the proprietors at Northern Greenhouse Sales, and they’re nice folks to deal with.
In business for almost 30 years, they specialize in strong, UV protected woven greenhouse covers and also carry pond liners and poly for haystack covers and other outdoor projects. Tell ’em Clair Schwan sent you.
Details
The raised beds were constructed first using transmission class power poles. Inside the beds, the poles were lined with corrugated metal to prevent soil from touching the preservative treatment of the poles.
The sides of the poles adjacent to the walkway were lined with a 22 mil woven ripstop white poly.
This keeps the dirty power poles away from the user, and reflects lots of light to maker a bright interior.
The photo above shows the white poly and corrugated metal that covers the power poles, the angle bracing on the walls, the joists, and the diagonal bracing that provides support between the roof purlins on one side of the structure and the power pole foundation on the opposite side.
Orientation of the beds is east to west, as is the case with the first greenhouse, thus the resulting structure has a wonderful southern exposure.
Tucked back up against a nice line of tall spruce trees, it is protected from NW winds.
In order to build a greenhouse like this, heavy equipment is required to create the foundation. I used a skid steer and a backhoe.
The skid steer dug the trench for the walkway, and the backhoe was used to maneuver the power poles into position.
Caution: this is dangerous work since the power poles weigh about 1,000 pounds each, and I used 8 of them.
You can’t let one of these things plop down on you unless you want to be included as a permanent fixture in your homemade greenhouse.
The upper structure of this second greenhouse is primarily steel tubing, with wooden framed ends.
The steel tubing makes the building strong, lightweight and easy to construct. It also reduces the shadowing that would occur with wood framing.
Since the material and fasteners are common, you save money by not needing specially made steel tubing from an out of town source.
The photo above shows the trellises attached to the joists and diagonal bracing. Also, the wooden framed end section is shown.
And, you’ll notice that our winter squash plants have just been set into the soil beneath the fabric mulch.
The steel tubing is of an exterior grade, so it should last a lifetime without any concern about mildew or rotting that you would have when using lumber.
In addition, lumber should be painted, and this galvanized steel tubing comes with an external plastic sealant.
Metal tubing used for the walls, rafters, joists, bracing and top plates consists mainly of chain link fencing top rail on 2-foot centers.
Chain link end clamps, and some electrical conduit (EMT) elbows are also used. Fasteners are large spikes, machine screws and carriage bolts.
Since we have high winds out here on the prairie, most everything has a nylon locking nut, a double nut, and is glued to prevent nuts from backing off on the threads.
This homemade greenhouse has rafters just like the wooden ones in greenhouse #1, except they are metal tubing instead of lumber.
The rafters tie into a set of roof purlins, one on each side of the building. Due to the rigidity of the roof, there is no ridge piece.
We wondered if this design would be a good idea for growing squash.
Well, take a look at the picture below and compare with the picture above, and decide for yourself.
It’s clear that the environment is conducive to growing squash as these two “brutes” went unnoticed in our homemade greenhouse.
Also notice how the winter squash has taken to the trellises and grown up over the sunken walkway to reach the south side where we grow the summer squash.
I guess they’re just not satisfied with their 3 by 36 foot bed. They want more room to stretch out.
Fine with us, the overhead fruits make harvesting from the homemade greenhouse just that much easier.
After our first season, the winter squash yield was about 175 to 200 pounds from 12 plants.
The summer squash yield was about 275 to 300 pounds from 12 plants.
We’re set for squash this winter thanks to homemade greenhouse #2, now fondly referred to as The Squash House.
Five diagonal braces run perpendicular to the building.
They start at the sole plate (power pole base) and end at the purlin on the opposite side that ties the rafters together.
If the wind or snow is going to provide a roof load on this homemade greenhouse, it will be transferred right to the foundation.
Ceiling joists cross between the 5 pairs of diagonal braces and are tied into the diagonal bracing.
Angled wall bracing runs the full length of the building on both sides and eliminates the need for purlins on the 5 foot high walls.
All this bracing makes for a very strong structure.
The photo below shows how the joists and diagonal bracing are tied together to make very strong support for the walls and roof.
This photo also shows the purlins that are tied to the rafters, and the EMT 90 degree conduit that forms the ridge by connecting the ends of two rafters at the peak.
Wooden framed ends are used on this homemade greenhouse for several reasons.
First, the wooden frames at the ends allow vents and fans to be framed and attached easily.
The aluminum frames of the vents and fans can be screwed into the wood to hold them in place.
This would be difficult if the framed ends were made of steel tubing.
Second, the wooden framed ends allow the UV protected ripstop woven poly covering to be attached easily with staples.
Again, if steel tubing was used, it would be much more difficult to get the poly covering stretched and fastened in place.
The UV protected poly covering is stapled on the wooden framing, and screwed into the metal framing.
In either case, white plastic lath is used to help hold the ripstop poly in place.
The overall design of this homemade greenhouse is like a simple peaked roof on a single car garage.
It sheds snow easily and catches lots of light from the sun.
The drawback of the design is that the power poles take up quite a bit of room inside the structure – about 3 square feet per linear foot of the raised bed.
This is the price you pay for having heavy no-cost materials that won’t sag or deform.
It is also the cost of the sunken walkway that allows you to simply reach out and get your harvest without bending over.
The overall dimensions of this homemade greenhouse are about 12 feet by 36 feet, with each of the two planting beds measuring roughly 3 feet by 36 feet, with a 3 feet by 36 feet long walkway running down the middle of the two raised beds.
The telephone pole walls that run the length of the walkway consume about 3 feet of width.
Let me offer a note about heating this homemade greenhouse. The walkway is filled with about 18 inches of moist sand.
I say moist sand because the structure is located directly over a portion of my leach field, so the soil stays moist from the constant evaporation.
(Not to worry, I have an alternative location for the leach field should it fail some day and need to be replaced.)
Beneath the 18 inches of sand is a single 200 foot circuit of three quarter inch Pex piping. This piping will be plumbed into a steel tank with a pump.
The pump will circulate about 20 gallons of water through 3 flat plate solar collectors and then into the underground piping.
This will make the sand-filled walkway act as a thermal battery to collect heat during the day and slowly release it to the homemade greenhouse throughout the night.
A waste oil heater will also be connected to the water circuit so the solar panels can be bypassed and the water heated directly.
The heater will be housed in its own “doghouse” outside the homemade greenhouse.
This will allow occasional supplemental heating without the need for a heater taking up precious space inside.
If you are going to build a homemade greenhouse like this, and you don’t have power poles, you can skip the sunken walkway and just make the walls taller, say 8 to 10 feet.
It should work just fine as long as you make the walls tall enough to get the diagonal bracing well overhead and out of your main walkway down the middle of the structure.
If you make the walls taller, you might want to add a purlin on each side wall, and shorter cross bracing with a sharper angle.
The cross bracing would bridge across the last 3 or 4 upright pieces of tubing at each end, with the upper ends of the cross bracing meeting up with the framed ends of the building.
Note: if you add purlins on the walls, they will not allow the cross bracing to lay flat against the walls. This is why my structure uses tubing that acts as a combination purlin and angle brace.
With a little bending of the angle brace tubing, you can probably weave it around the inside of the purlin as it passes from the top plate at the wooden end framing down to the foundation, and then tie it into the purlin and wall tubing pieces with fasteners. (See homemade greenhouse #3 for an example of angle bracing that was woven around the purlin and ribs.)
In the absence of power poles, a concrete foundation would work well, or make the sole plate out of horizontal steel tubing and use end clamps to connect the walls to it.
Then, anchor the sole plate to the soil with lots of long stakes or earth anchors.
The photo above shows how end clamps are used to tie together the top plate, wall tubing, rafters and the joists.
If no foundation is used, these end clamps could attach the bottom of the wall tubing to a soleplate. Note the double nutting on each threaded connection.
If you have power poles and don’t want the sunken walkway, you can simply bury the power poles level with grade and start from there.
I would wrap the power poles in poly before burying them to keep the preservative treatment from touching the soil.
In hindsight, the following are things that I would do differently, and the reasons why.
- Provide toe kick space of about 6 to 8 inches to make it more comfortable while standing next to and facing the raised bed.
- Build in vents in the roof and sides for cooler operation. These will be installed soon to reduce high temperatures on warm full sun days.
- Lower the height of the walls to about 3 feet to reduce overall solar capture and have a lower profile structure.
- Install a ridge piece so the ripstop poly can be fastened in between each rafter up at the ridge. This will be installed soon as an improvement on the ropes that hold the poly bulges in place at the ridge.
- Orient the wall braces so that the upper portions meet up with the wooden framed ends of the building, instead of in the middle at the top plate. This would add more strength to the building, but would require some additional design work to make a point on the power pole foundation to secure them.
The foundation is all “no cost” material for this homemade greenhouse, and the rest of the structure is readily available at the hardware store and salvage yard.
Indeed, this is a greenhouse for those that are frugal living minded; and those that simply love squash.