Lettuce growing in my cold frame.

When I built my 50 dollar greenhouse over a year ago one of my goals was to be able to have something fresh to eat out of the garden or greenhouse every day of the year.  Well, it’s been about a year now, and  it hasn’t even been very hard to do.

Here is what I’ve learned so far -

Despite what you might have read, lettuce spinach and other salad greens are not really  particularly quick crops.  Sure you can have a pretty little stand of plants in about 6 weeks or so under good conditions, but  in cool weather  they don’t really get productive until they are  almost 3 months old.  Yes you can harvest a few salads out of the thinnings, but the young plants  aren’t going to yield an every day supply unless you can plant a pretty large area.

When it gets cold, growth slows way down.  However, on sunny days the temperature under glass (or plastic) is balmy, and I’ve continued to see steady growth all winter long.  What should be done in the fall is to have a lot of greens grown out as much as possible before it turns so cold that growth slows down.

It’s quite difficult to get those cool season crops to grow productively in Tennessee until late into our rather warm autumns, but once it gets to be jacket weather they do great.  Same thing in the spring – once the nights get warm they fail or go to seed.  So the easy thing to do is to seed dirrectly into a cold frame or green house in September, then seed again every few weeks all winter long and you can have fresh lettuce and spinach from  before Thanksgiving until June.  Last year I had tons of productive growth by late winter/early spring.

You can not only grow, but garden in relative comfort all winter long in a simple greenhouse like my $50 hoop house.

These crops are almost completely freeze proof – especially spinach.  I’ve had temperatures down to 5 degrees with only minor damage to lettuce and none to spinach inside of a frost encrusted cold frame, and even less damage inside of the hoop house for some reason.  It’s easier to keep them growing in cold weather than to keep them from bolting (the elongation associated with going to seed which triggers instant bitterness) in early summer.

One of the beautiful things about cool weather gardening is the absence of insect and weed problems.  There are usually a few of both, but not to the point of being a problem.  Also having productive plants growing in January is really therapeutic to a gardener with cabin fever.

This picture was taken on Nov. 5 - with a little bit of effort (and a cold frame) your garden can be productive almost year around.

I’ve only mentioned cool weather plants in this post, but it’s worth mentioning that in my area most gardens go to the weeds by early August when they don’t have to.  If you want to have a 4 season harvest you have to plan and plant in all 4 seasons as well.  I’ve found that the late summer – early fall is probably the most challenging time because it is hot and dry, and insect pests are at their peak, and it just isn’t very much fun.  Nonetheless with just a little timely effort you can keep your garden productive by planting the right thing at the right time and also yanking out old plants once they stop being productive.

This plastic tunnel is being used inside of the greenhouse to protect tender plants against a late hard freeze - very effectively I might add.

A simple plastic tunnel like this can serve as a cold frame to grow salad greens  all winter long, to grow out tomatoes and other tender plants, to extend the season for an early Spring start or a late Fall harvest, or even as a screen house to keep birds off of your strawberries or vine borer moths off of your squashes.  You can also use one of these to dry out water logged beds and warm up the soil so that you can begin planting  in early Spring. These devices are so useful, cheap, easy, and quick to build that everyone should have at least one – it’s almost as good as having your own polytunnel greenhouse.

materials for plastic tunnel row cover

Materials:

• 5-5′ lengths of 3/4″ (inside diameter) polyethylene water pipe
• 10 – 1/2″ x 1/2″ x 14″ wooden stakes
• 1 – 12′ x 6′ x 4 mil clear plastic sheet
• 4 – 1/2″ x 1 1/2″ x 8′ wood strips
• staples and nails.

As usual you can (and should) substitute materials that you have available on hand.  You can use anything for stakes that are strong enough to drive into the ground and will slip inside of the rib pipes. You can use a broom stick, piece of pipe or any long thin objects for the poles, and you can fasten the plastic skin to the poles with duct tape instead of staples.  Clearly almost any kind of bendable pipe can be used for the ribs, but here’s a tip – contractors or plumbers are likely to have a scrap collection of one kind of plastic pipe or another that comes in coils that they will either give away or sell incredibly cheap – just ask.  In the worst case, you can usually buy cut lengths at the home improvement or hardware store.

This design is also great for hardening off. The cover can be opened or closed in about a minute by one person. The whole thing can be moved to a new location and set up in 15 minutes.

Start by cutting your parts to size – this tunnel will cover an area that is from about 2 – 3  feet wide and the black pipe for the ribs are 5′ long, and the plastic is about a foot and a half wider – you can roll up any excess plastic on the poles so it is better for it to be too wide than too narrow.  In this case I made the poles shorter than the plastic so that the excess could be used to close up the ends, but you could also make the poles the same length as the plastic and use rectangles of plywood or other sheet lumber to close up the ends.  Use your imagination.

Once you have your parts cut to size fasten the poles to each long edge of the plastic sheet.  I used staples to do this, and then rolled the plastic around one piece of wood and fastened another strip to it so that the plastic is sandwiched between the wood pieces.  If you are just using tape, then you will want to wrap the plastic around the pole and tape the plastic sheet back to itself forming a tube with the pole inside – tip: construction tape (duct or housewrap tape) sticks very well to plastic, and not very well to wood – don’t try to tape to the wood other than as a temporary measure.

Once you have that done, roll the plastic up around one of the staves until you are ready to deploy it.

The ribs just slip over the stakes - you can probably get by with ribs that are much further apart than this if you want.

In the garden, simply drive the stakes into the ground where you want them, and slip the pipes for the ribs over them.  Since my ribs are made out of coiled pipe they already have the right shape, if you used straight sections of pipe you might need to use something more robust than 1/2″ wooden stakes to hold against the tension of the polytunnel ribs.

Now just roll your plastic out over the ribs and there you have it.  If you experience a lot of wind you might need to weight down the plastic a bit, but under normal conditions the wooden pole will probably do the trick.  When you need to get into the pollytunnel you just lift a pole and lay it over the top – almost as easy as a regular cold frame, but a lot easier to build or move.

Now would be a good time to build one!

Welcome back Stumbleupon Gardeners!

If this looks like too much work – I did a much simpler door on the other end.

This weekend I finally got time to start on the doors for my 50 dollar greenhouse.  The design that I came up with is light, strong, simple, and can be built easily and quickly using only a circular saw and a hand drill.  I must admit that I did use a table saw to rip out the stock, and put it through a planer to accurately dimension it, but this was only a convenience, and isn’t at all necessary for a good result.  This polytunnel door design can be built on a set of sawhorses out in the driveway, but it will be a lot easier if you get someone to help you hold things while you saw, drill and fasten parts together.

Needless to say you can seriously hurt yourself with power tools, and you should follow all applicable safety rules for the tools that you use.  No kidding, a friend of mine lost an eye about a year ago because he wasn’t wearing safety glasses.  Don’t make a mistake like that.  Be Careful.

You will need enough 1×2 stock to make your door – two pieces to make the sides, and three pieces to make the top, bottom and middle brace.  The dimensions of these pieces will be determined by the size of the door that you are making to fit your polytunnel  hoop house.  The sides need to be the same length as the finished height of your door while the top, bottom, and brace need to be 3 inches less than the width of the finished door.

Pre-drill holes before screwing the frame together.  If you don’t pre-drill you will probably have problems with your wooden parts splitting when you drive the screws.  Use a bit that’s just small enough to allow the screws to get a good bite.  Try it on a scrap of wood first to make sure that you aren’t pre-drilling too loose or tight.

I used 3″ washer headed self drilling screws (I still had to pre-drill the holes though to prevent splitting) but any 3″ screw would work. If there’s a gap between the parts after you screw them together – back out the screw and re-drive it.  There is no point in gluing these joints because glue doesn’t hold very well on end grain – trust me, don’t bother – the finished product will be very strong anyway if you follow the plan.

Your frame should look something like this after you screw it together.

Now drill a hole in each corner to thread the brace wires through.

Thread a loop of wire diagonally both ways and secure the ends by twisting them together, and then twisting the tags back around the main wires. I used galvanized electric fence wire for this, but you can get a similar product called “utility” wire at any hardware store or home improvement center.  You can also use small rope/large string, but wire is really better because it isn’t as likely to stretch.

Clip the ends off and bend them neatly so that they won’t stick out and snag people, clothes, or greenhouse plastic. There has to be a better way to do this than I’ve done here.  Gotta’ look into that.

Check your frame for square by measuring diagonally across the corners.  If they aren’t about the same then tweak the frame a bit to get it pretty close to square. Although this is a pretty forgiving design and unless it’s really  out of square it probably won’t matter much – within a quarter of an inch is great.

Now use some scraps of wood to tension the wires.  You want them to be merely tight, but not like guitar strings – just without any slack.  This will pull all of the joints together so that they aren’t likely to come apart or sag.  Check for square again to make sure you haven’t torqued everything out of whack.

This is how the tensioners finish off.  You may have notice that I’m a fan of this kind of device – I used it on my polytunnel greenhouse for the same reason that I’m using it here – It’s strong, light, easy, and it works.

Now glue triangles of plywood at each of the frame intersections – the corners, and at the cross brace.  Notice the pencil marks to help keep the glue in bounds.  Use a water proof glue like Titebond 3, and secure the connection with screws or nails. I used scraps of 1/2″ plywood for this, but anything from 1/4″ to 3/4″ sheet goods would work, or even solid wood, but lightness is a virtue so mind the weight. I used what I had.

You will be amazed at how strong and light this structure is. You can certainly use other sizes of lumber instead of 1×2 to make your doors – 1x3s would also work great for the sides, and 1×4 or 1x6s would be fine for the other parts.  However,  your door will be heavier (although it might be stronger), and you will probably have to recess the screws that hold it all together so that you get enough penetration for them to hold – or find some really long screws. You will of course have to adjust the measurements to work with your door size and the lumber that you use. Keep in mind that if your door is very heavy it might be more than your polytunnel greenhouse frame can support without some beefing up.

When I turned my frame over I discovered that some of my screws were just a tad too long, and they poked through the other side.  This had to be fixed or it would cut the plastic covering and would probably cut me or someone else sooner or later.

Just a few strokes of a file on each screw takes care of this small issue.

Nice and flush.

Now for the Plastic – After building the greenhouse I discovered that condensation and rain will collect at the bottom of the plastic if it can, so don’t fold the plastic around the bottom of the door just staple it flush so that water can run out the bottom.  On the sides and top leave a little extra to fold it around and double it up…

Like this.

Plain old (recycled) loose pin interior door hinges are fine for this application – be sure and install them right side up though so that the pins don’t work loose and fall out.  With regular gate hinges the pins would be attached instead of loose and you couldn’t remove the doors as easily (by tapping the hinge pins out) when the weather turns warm next summer.

Another recycled item.  You could also use a cabinet knob, or just a piece of 2×2 for a handle, or even a strap of leather from an old belt.

Ready to go…  Wouldn’t you like to explore that shop?  I used to love the “Mister Wizzard” TV show when I was a kid, and my life is now complete that I have a shop like his.  Now all I need is a box on the shelf labeled “Dinosaurs” – I always wondered what was in that box.

Because of insufficient foresight  I have this “situation” that I had to deal with before I could hang my door. The door frame needs to be unobstructed all the way to the ground.

I took the quick and dirty route of shoring up the problem spot with plastic and a scrap of galvanized metal after trimming the wood off flush.

Now that you’re ready to hang the door put a scrap of lumber under the door first to space it off of the ground.  Since my polytunnel greenhouse site slopes, I only needed to do this on the high side.

Now just set the door down on the spacer and screw it temporarily to the greenhouse in just the position that you want.  Stand back and take a good look for obvious problems before you continue.

I made my door about an inch and a half wider than the door opening on the greenhouse and a couple of inches taller because I want the door to close against the greenhouse itself instead of using a door stop.  If you have much snow you might want your doors to open in – think about what your needs are, and adjust the design to do what you want with the materials that you have readily available.

Now, hold a piece of lumber that will be the jamb right against the side of the door and mark about a quarter inch above the top of the door.  Cut it off at this mark, and do the same thing on the other side.  Then screw the two resultant side jambs securely to the greenhouse leaving about a quarter of an inch of space between the jambs and the door.

The 2x4s that I used for jambs are 1/4″ thicker than the actual door – this turned out to be a good combination because it left enough space between the door and the greenhouse for the door to open and close easily, but because the polytunnel plastic is a bit poofy there isn’t really much of a gap for air to leak through.  Serendipity I guess. If you do have problem gaps you can weather strip with scraps of foam carpet pad (or even carpet) and your staple gun.

Once you’ve attached the jambs you can screw the hinges to them, and remove the temporary screws that have been holding the door in place. At this point the door should open and close easily – if it binds or rubs excessively, back up and adjust before you go on.  A common error would be to make the space between the door and the jambs too tight.

Now cut a piece of lumber to use as the head jamb.  I ripped an angle on mine so that it would shed water better.  I stapled the strip of black plastic to the back before attaching the head jamb.

The strip that was ripped off is then attached to the front to extend the jamb and give an overhang so that rain won’t run over the door. You could actually accomplish the same thing by just using a 2×4 that lays flat for the head jamb and letting it stick out.

Then, just staple and trim the plastic strip thusly.

Add a simple turn bolt both inside and out and your door is finished.  Almost finished – I shoveled a bit of dirt in to close up the gap under my door, and I will probably add a simple sweep to the bottom later.  But for now it works great, and looks fine. It’s easy to open and close even with just one hand.

On the other end of the hoop house I did something much simpler – basically a well secured curtain.

Secure two or three pieces of string at the top of the door opening – these will be used to tie the curtain open when you have it rolled up in warm weather.

On both sides of the door opening apply two strips of wood leaving a gap between them.

Hang the curtain by wrapping the top of it around a stick and then screwing it to the greenhouse.

Put two or three turn bolts on each side

To fasten the curtain shut push a stick into the gap on the sides..

And secure it with the turn bolts.

And that’s it.  It isn’t as convenient to open and close as a hinged door, but it gets the job done.

Now that the doors are up it gets pretty warm in the polytunnel on a sunny day even when it’s cold outside – I have the same problem with my cold frame.  Next time I’ll give you the scoop on some really easy automatic vents that you can make for about $10 – $15.  Subscribe to the DoorGarden RSS Feed and you’ll never miss a thing.

Thanks for coming by! How about a thumbs up if this is helpful?

]]> http://doorgarden.com/11/building-greenhouse-doors/feed 21 http://doorgarden.com/10/50-dollar-hoop-house-green-house http://doorgarden.com/10/50-dollar-hoop-house-green-house#comments Mon, 27 Oct 2008 04:27:26 +0000 David LaFerney http://doorgarden.com/?p=44

My $50 Greenhouse

Welcome Stumbleupon Gardeners! How about a Thumb up if you like this article?

Materials list

Construction Steps

Hind Sight – What I would do differently

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 $50 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 polytunnel It would still only come to about $120 $150 – 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 $50 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 $90 for the roll – so in essence I used about $22 worth of plastic sheeting after you apply the 10% TN sales tax. Had I ordered real green house plastic from littlegreenhouse.com a similar sized piece of 6 mil plastic would have been about $71 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 – as pictured this greenhouse structure alone won’t stand up to snow accumulation.  But if you put a 2×6 or 2×8 ridge pole right down the middle to keep the peak from sagging it will be a lot stronger.

I strung it all together with 1x2s that I ripped out of some slightly used 2×4 studs.  Using full 1x4s 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:

Complete Materials list for the “$50 Greenhouse” – As Built

Each      Qty    Total
$4. 23   6        $25.38           20′ x 3/4″ PVC schedule 40 plumbing pipe
$6.70    6        $40.20           1x6x8′ pt – ripped into 1x3s
$4.99    4        $19.96           8′ steel “T” fence post
$2.18    3        $6.54             2×4 stud – rip into 1x2s
$3.97    2        $7.94             1x4x12′ pt
$5.73    1        $5.73             2x4x16′ rip into 2x2s
$7.91    1        $7.91             20′x1/2″ rebar – cut into 18′ lengths
$4.88    .75     $3.66             8″ nylon wire ties – 100
$5.47    .5       $2.74             1 1/4″ x 1lb drywall screws
$6.97    .3       $2.09             16 guage galvanized utility wire – 200′ – for X braces
$2.97    .25     $0.74             3/8″ t-50 staples – 1000
$79.00  .22     $17.38           20′ x 100′ x 6 mil clear plastic
Scraps of plywood for reinforcements – scrounged
$140.27      Total

In the comments:

Deb says: August 23, 2009 at 5:36 am

OK, that’s a bit more than I estimated because I didn’t count all of the minor bits that I just take for granted because I buy them in bulk and keep them on hand.  These prices are what you would pay if you just bought the quantities that you need for this project.  Drywall screws for example are only about a third as much when you buy a 25 lb box like I do being a contractor.    However, you can shave most of the 20 dollar overage by using 5/8 rebar instead of fence posts, and gray UV resistant PVC conduit which is actually less expensive than the non resistant white plumbing pipe that I used – you can also do without wire ties, and use scraps of wire instead, etc.  I already had everything on hand except for the PVC pipe and a couple of pieces of 1×6 lumber.  However, surely almost anyone can get some of this stuff for cheap or free if they put some time and effort into it – so shop around and use your imagination to find what will work best for you.

Admittedly it might be hard for most people to build this for just $50 out of pocket, but then again a serious scrounger can probably do it for even less.

Hind Sight – What I would do Differently

1. As originally built this hoophouse design is subject to collapse under even a moderate snow load. It has to be beefed up a bit.
2. Use UV resistant gray PVC Conduit instead of white plumbing pipe – it should last longer and is actually less expensive
3. Use UV resistant greenhouse plastic instead of “visqueen” construction plastic – It’s a good bit more expensive, but I’m so pleased with how the polytunnel turned out so far that I’m pretty sure the investment in durability would be worth while.  However, if the extra expense meant putting off the project I would go ahead and use the cheap plastic because  1) The plastic will have to be replaced sooner or later anyway and the difference in cost seems proportional to the difference in life span 2) It wouldn’t be worth putting off having a perfectly usable greenhouse.
4. I should have painted the PVC pipes with latex paint before applying the plastic sheeting – apparently this makes the poly sheet last longer, and maybe makes the frame pipes more resistant to UV.
5. Site Selection – As you can see in the pictures my garden is in a clearing in the woods and the truth is it doesn’t get as much sun as I would like for it to – however I can still grow a nice garden – it just doesn’t yield as much as it might.  I can’t really do very much about this, but you should keep in mind that you want as much sun as possible as well as a sheltered well drained spot that is as close to the kitchen as possible so that it isn’t too much trouble to trot out and get a bowl of fresh lettuce for supper. All that being said – do the best you can with the spot you have, and you might be surprised with the results you can get with a little effort.
6. Next time I think I will use screws and  battens made of plywood strips to secure the main skin to the end walls (I’m not talking about the end wall skin here) so that instead of using 200 staples I will use a couple of dozen screws to accomplish the same thing, but it will make it quicker to put up and take down.  When I do it I’ll add pictures for clarification.

BTW, Stumblers – Thanks for all the thumbs up.  Feel free to hotlink the images or scrape the text as long as you leave the links intact!

Other homebuilt greenhouses:

• Another PVC greenhouse – quite similar to mine but with a few differences that are very worth looking at.
• A great wood framed greenhouse design – great construction details.
• An excellent article on high tunnel greenhouses by The University of Vermont.

The Greenhouse doors are built now and my small hoop house is complete.

Update – Dec. 10, 2008 – we had 2″ of rain and 30 mile per hour winds last night and so far so good – no damage to the greenhouse.

Does it really work? Does the wind blow it away?  Is it even worth the effort?  Read 6 months in the Greenhouse.