How to build Rs.3K INR Eco-Friendly Greenhouse
· First off – you really can build this thing very cheaply, but to
do so you have to recycle, free cycle, and borrow. If you just go out and
buy new everything it will probably cost over Rs.10000 INR.
Want to find out if this thing works before you read all this? Read 6 months in the Greenhouse first.
Want to see what happens when a few inches of wet snow accumulates on this? Collapse!
Building the Greenhouse Doors is addressed in a separate article –
Want to find out if this thing works before you read all this? Read 6 months in the Greenhouse first.
Want to see what happens when a few inches of wet snow accumulates on this? Collapse!
Building the Greenhouse Doors is addressed in a separate article –
isn’t all this enough for one
weekend?
The planning is over and construction on my hoop house greenhouse has begun. I’ve
rounded
up all of the
materials and it looks like I’m going to end up with about 3000Rs in a 165
square ft. green house. Granted I already had most of the materials because I’m
an incorrigible pack rat, but even if I had bought everything new just for this poly tunnel It would still only come to about Rs.6000 Rs.7500 – less than a dollar per
square ft. Due to the fact that we are in the midst of a global economic
meltdown, and the future is a bit uncertain keeping the cost of this project as
low as possible is an important consideration.
After some research I’ve decided to
build the structure of the hoop house out of 20 ft. joints of three quarter
inch PVC plumbing pipe. Some similar greenhouse designs that I’ve run
across use 10 ft joints of pipe and then fasten everything together with pipe
fittings, but I’m saving quite a bit of cash with the long joints of pipe and
by not using any fittings – also overall simplicity is improved. There is
one thing though, you can carry 10 ft joints of pipe in the mini van, but
hauling 20′ pipe requires a truck and preferably a ladder rack. However,
you could just cut them in half right at the home improvement store and then
put them back together when you get home with the coupling that is built into
one end of the 20′ long pipe joints – 10′ pipe joints don’t have the built in
couplers – just go to the home improvement store prepared with a saw or pipe
cutter.
My hoop house green house is going to
be 11 feet wide and 15 feet long, and will be about seven and a half feet tall
in the center. You could make one of these as long or as short as you
want, but using this design the width needs to be between 10-12 feet. 11
feet wide just happpened to work out with the layout of my garden which has 3
foot wide beds with 5 ft paths between (the wide paths are so that I can keep it
tidy with my riding lawn mower) so eleven feet covers two beds and the path
between them. This width also makes the sides go fairly straight up from
the ground for the first few feet – I’ve noticed that in some hoop house /
polytunnel designs the outer edges are almost unusable because of the slope of
the greenhouse sides.
If your Greenhouse is too Flat
it will collapse!
You might be tempted to make your
greenhouse wider and lower at this point to get more floor space out of it –
but be careful. If you have snow in your area it will slide off of a high
peak a lot better than it will if your greenhouse has more of a flattened shape
– and the same goes for heavy rains. If your hoop house shape is too
flattened it will cave in the first time it snows or rains really hard!
How to Build the Rs.3000 INR
Hoop House
I decided to begin the construction by
building the end walls first – even though it would be more fun to throw up the
main structure in just an hour or so and make a big showing of progress, I
think that in the long run it will be quicker and easier to build the end
frames first on my garage floor.
I temporarily attached
a joint of pipe to a piece of 1x4 to establish the outline. You might be
tempted to make your greenhouse wider and lower at this point to get more floor
space out of it - but be careful. If you have snow in your area it will slide
off of a high peak a lot better than it will if your greenhouse has more of a
flattened shape - and the same goes for heavy rains. If your greenhouse is to
flattened it will cave in the first time is snows or rains really hard!
Pre-drill the pipe and
use one screw so that the pipe can swivel to whatever angle it naturally aligns
to. For now just let the wood "run wild"
I used pressure treated lumber for much of the
polytunnel end frames even though I usually try to avoid treated wood in the
garden. In this case I think it’s called for or else the greenhouse
probably wouldn’t last more than 2-3 years without rebuilding the frame.
In any event I’ll try to keep it off of the soil as much as possible.
Build the rest of the
frame to accommodate the door size that you want to use. My door will be 5 feet
wide, but in most cases 3' wide would be adequate. If you want a more permanant
greenhouse or you live where you will ever get more than an inch of snow you
should use "two by" lumber instead of "one by" that is
shown here.
Leave the piece that runs across the bottom of
the door in place for now. Once everything is set in place it will be
easy to cut out with a hand saw.
I used a bit of weather
resistand glue at all of the joints to help make it all more rigid. Notice the
wood recycled from concrete form lumber.
Mark the final outline
once the wooden parts are assembled. Watch out for that screw when you saw to
the line!
Now just trim to the
line - I used a reciprocating/sabre saw, but you could also use a hand saw or
circular saw if it's all you have. Just make a straight cut in about the right
place.
Now re-attach the pipe
to the outside of the frame. I used screws and wire ties because I'm a belt
*and* suspenders kind of guy.
The end wall frames ended up being reasonably
light and very rigid. BTW, you might notice that the second one is different
(simpler) from the first because this is a learn-as-I go process. Both of them
work fine though.
back side of the green
house end frame
and the front side...
Notice that the plastic that will be the roof and sides of your greenhouse are
going to fold over the ends and staple to the wooden parts. If you don't have
enough wooden structure in the ends you won't be able to fasten the plastic and
you will have trouble with it coming lose when the wind blows - and during
heavy rain or snow you will be more likely to have problems with the very top
sagging and holding water (or snow). If the top sags, it holds water, that
makes it heavy and it sags more, then it holds more water... eventually it
collapses. You don't want that
This is the front side because it is all on
one plane so that the plastic skin will lay flat on it. The back side has
reinforcement gussets that stick out.
And Now for the Plastic
The plastic sheeting
that I’m using is plain old non-UV stabilized 6 mil “clear” plastic sheeting
from the lumber yard. There is exactly one reason that I am using
this particular variety instead of special polytunnel / greenhouse plastic –
it’s what I have. I cut a 22′ piece off of a 100′ x 20′ roll that I
already had (I’m a contractor) which was about Rs4500 for the roll – so in
essence I used about Rs.1100 worth of plastic sheeting after you apply the 10%
TN sales tax. Had I ordered real green house plastic from little green house.com a
similar sized piece of 6 mil plastic would have been about 3600 with shipping.
The real deal would no doubt last much longer than the “visqueen” that I’m
using, and also probably has better thermal and light transmittance. If
all goes well maybe I’ll get some of that next year. Also, It’s hard to buy
large pieces of heavy duty plastic like this without buying a whole roll, so
unless you know a contractor or Mom and Pop hardware store that will cut you a
piece you might really be better off ordering some of the good stuff. On
the other hand a big roll of plastic sheet is one of those things that comes in
awfully handy some times.
I just rolled the
plastic out on the frame... Notice the falling leaves - I'm racing against fall
weather with this project.
and cut it off nice and
clean with a sharp utility knife. A scrap of wood to cut over and a sharp knife
make this much easier.
after stapling the
plastic to the front, flip the frame over and fold over the plastic and staple
it to the back. Just fold the excess together as you go. Fold in the direction
that will be down so that condensation won't collect under the folds.
then trim off the
excess. Be careful not to make a miss-cut!
Cut the plastic out of
the door opening - leave enough to fold double before stapling it to the frame.
Notice the cuts back to the corners of at the top.
Thusly
Mark out the locations
of the door sides on the ground, and drive fence posts or long pieces of rebar
at the sides of the door frame.
If you have much wind I would recommend using
steel fence posts or rebar that is at least 5/8″ diameter in these spots. My
fence posts don’t match because they’re left overs from previous projects –
remember, I’m on a tight budget!
Check the fence posts
for plumb and bend them a little if they need straightening.
Tie the hoop house end
frames to the fence posts with wire ties, wire or rope.
The humongous wire ties made this really quick
easy and strong, but If I didn’t already have them I would just use “baling”
wire, and it would work as well.
Once the end frames are
in place pull a string to line up the stakes for the ribs.
Drive rebar pins every
3 feet to secure the intermediate ribs...
At this point it takes
about 2 minutes to install the pvc pipes for the intermediate ribs - and the
polytunnel takes shape. For a stronger, more permanant structure use more ribs
and put them closer together - or even use larger pipe. I haven't tried it but
I bet you could use up to 1 1/2" pipe - although you might have to bend it
into shape on a warm day.
As you can see it’s getting dark, and I’ll
have to finish this later. Total time invested so far is about 2 1/2
hours. I believe that taking the greenhouse down next summer, and
re-assembling it in the fall will probably only take an hour or so, but I guess
I’ll see about that.
Since the site location where I’m building my
greenhouse isn’t all that level I had to raise up one side of the end frames
with some 2x6s that I ripped to fit – later I cut the tail off where it sticks
out toward the fence. Also notice that this means that the PVC pipes that
are the intermediate ribs are too low where they hit the ground…
So I extended them
with some scraps of PVC conduit that I had – I never throw anything away. BTW,
the gray PVC conduit is sunlight resistant unlike the white – although somewhat more
expensive and is less
expensive! If you want to do a really good job you could use it instead.
You should probably use the gray conduit instead of the white pipe
that I used. You could even opt for schedule 80 conduit which is much thicker
if you wanted to go whole hog, or if you needed to make a structure that is
sturdier, more permanent or wider.
If you live where it snows or
even rains very hard – You need to add a 2″
pvc pipe to the very top of the frame like this:
This 2" PVC ridge
on TOP of the frame keeps the plastic from sagging in snow or hard rain and
prevents the structure from collapsing.
I ran a screw up
through the ribs into the 2" ridge pipe, but I also tied a peice of
1/4" rope around each intersection as well - I don't trust screws alone in
a spot like this.
When I originally built
the greenhouse I didn’t use the ridge pole and it collapse under a snow load.
Since adding this feature It has been through several snows with no problem at
all. However when I know snow is coming I have two 2×4 props that I put
under the ridge as insurance.
I strung it all together with 1x2s that I ripped out of some slightly
used 2×4 studs. Using full 1x4s (which I later did) or even 2x4s for the
top set of these would make the structure stronger
I used a few wire ties to get everything
located, and then drove a 1 1/4″ drywall screw at each joint to secure
it. As you can see by the lay out marks, I first measured and marked all
of the locations so that it would go together reasonably straight.
If you look really close in this picture you
will see the wires that serve as X bracing on the sides.
I used a doubled wire that I attached at the
top and bottom of the ends using a washer and a screw.
I then used some scraps of wood to twist the
double wires together and tighten them up like a rubber band airplane.
You just want them to be snug so don’t go nuts tightening them up. These
wires really go a long way to make the whole structure more rigid and sturdy.
Now for the plastic covering – measure and cut
your piece of plastic – you want a little extra in all directions – the piece
that I used is 20′ x 22′.
My greenhouse is 15′ feet long so I cut a 2×2
x 15′ – Here I’m positioning it in the center of one of the 20′ edges of the
plastic – leaving 2 1/2 of plastic past the ends of the 2×2. Staple it
together just to hold it in position.
Now roll the 2×2 under one complete turn so
that the edge you stapled is facing up under the top layer of plastic sheet.
Now screw a 1×2 on to secure the plastic. By
wrapping the plastic around the 2×2, and then sandwiching 2 layers between the
2 pieces of wood you make a very secure connection, and also add some weight to
the bottom edges to help keep them from billowing up in the wind. Do the
same thing to the opposite edge, and then roll it all up and get someone to
help you carry it to the hoop house and unroll it across the top…
Thusly. Now you almost have a
greenhouse.
Roll under the edges
on the ends and staple them securely (Note: now that I have taken
this down for the summer, I think that when I put it back up next fall instead
of “stapling it securely” I’m going to just staple it a little bit to get it
positioned, and then screw battens made of 1×2 or strips of plywood to hold it
in place – it should be stronger and quicker), and other than the
doors the structure of your polytunnel greenhouse is finished. Total time at
this point – about 6 hours. Everything is a bigger job than it seems like
it’s going to be. Rake soil or mulch up to the gaps at the bottom to keep out
drafts and (larger) critters. Cats in particular are likely to be
attracted to such a nice sheltered spot with a bed full of soft loose dirt to
dig in so pay attention to the details. Rocks, bricks or concrete stepping
stones or blocks placed on top of the soil/mulch around the outside edges are probably
a good idea.
Here is a forum discussion on alternative ways to fasten plastic to your
greenhouse. I haven’t tried the poly pipe clips that are discussed, so I can’t
vouch for them, but it looks like a good idea that I would consider. Here
is a picture of a small greenhouse which uses that method:
This greenhouse uses clips made of sections of black poly pipe
to attach the skin.
Before I even started on the hoop house I
tilled copious amounts of compost into the beds where the greenhouse was going
to end up. So, even though I probably won’t get a chance to put up the
doors until next weekend (which is Halloween), I’m all ready to plant some
lettuce and spinach for (hopefully) some fresh mid winter greens. One of my
goals in building this polytunnel is to have something fresh coming out of the
garden or greenhouse all year long. That might be a little optimistic, but I’m
going to give it a shot.
Addendum:
Qty Requirements
6
20′ x 3/4″ PVC schedule 40 plumbing pipe
6 1x6x8′ pt – ripped into 1x3s
4 8′ steel “T” fence post
3 2×4 stud – rip into 1x2s
2 1x4x12′ pt
1 2x4x16′ rip into 2x2s
1 20′x1/2″ rebar – cut into 18′ lengths
.75 8″ nylon wire ties – 100
.5 1 1/4″ x 1lb drywall screws
.3 16 guage galvanized utility wire – 200′ – for X braces
.25 3/8″ t-50 staples – 1000
.22 20′ x 100′ x 6 mil clear plastic
6 1x6x8′ pt – ripped into 1x3s
4 8′ steel “T” fence post
3 2×4 stud – rip into 1x2s
2 1x4x12′ pt
1 2x4x16′ rip into 2x2s
1 20′x1/2″ rebar – cut into 18′ lengths
.75 8″ nylon wire ties – 100
.5 1 1/4″ x 1lb drywall screws
.3 16 guage galvanized utility wire – 200′ – for X braces
.25 3/8″ t-50 staples – 1000
.22 20′ x 100′ x 6 mil clear plastic