Tuesday, February 02, 2010

PVC Greenhouse: So you are thinking about an all PVC Greenhouse

I'm glad you are thinking about building your very own PVC Greenhouse. I found the project very satisfying and looked forward to all the time I could spend constructing it.

First, be sure that this is the right type of greenhouse for you. The choice to go all PVC should be made for the right reasons. There are some beautiful, professionally produced, greenhouses made of wood, metal, and (plexi-) glass that are very functional and could really be a show piece on the right property. A wood/PVC combo construction seems like another great DIY project.

I consider some of the main reasons to go all PVC as:
1) Price: PVC pipe and fittings are quite inexpensive ($0.17 a foot for the pipe). My total cost is about $150.
2) Light Weight: I built mine on a roof deck. The roof could support a greenhouse 50 times the weight of the PVC version but who wants to carry all that up the stairs.
3) Seasonal: The PVC greenhouse is made to be taken down in the spring. It breaks down to a medium size set of its main component parts. Everything should be long and thin and pretty easy to stash away.
4) Space: I am city dweller and, as such, I don't have a garage or easy access to a basement. I cannot overwinter my plants and shrubs indoors. At the same time, I have very limited outdoor space for a greenhouse in the winter and even less in the summer when I want to use my deck
for gardening and pleasure.

Full disclosure: This greenhouse has not been put to use for a single winter yet. There will be many challenges and the real success will be in the spring when (if all goes well) my plants and shrubs emerge from their winter slumber and thrive once again in the warmer weather.

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Monday, February 01, 2010

PVC Greenhouse: Sizing your greenhouse

When I get around to scanning my hand drawn plans for my greenhouse you will see that I intended a 6 foot wide, 10 foot long 8 foot high frame with ribs made of 10 foot pipe lengths. This planning was well intentioned but the resulting greenhouse was a monster. I know because I loosely assembled it and was awed by its size. I adjusted mid-course in a few areas and now have a more modest 5 x 10* x 6 high with 8 foot ribs. Let me provide some sizing guidance and tell you about my experience working with PVC.

*10 feet actually became 11 feet which I explain below.

Watch your greenhouse "grow"
Whatever the initial dimensions of your pipe lengths are cut to, expect them to grow a little as you assemble them. The reason is that each tim you cut a pipe to insert a fitting you are adding between 1 and 2 inches.

In my case, I started with 10 ft long 1 inch PVC for the long base pipes. I need to cut those 10 foots to insert the T--shape pipe fitting where the ribs attached at the base. Each of the six T-pipe fitting is 2 1/2 inches long. No matter how hard you try to shove the ends of the cut pipe into the pipe fitting you'll have difficulty getting them inserted flush. In addition, there is at least 3/4 inch of space in the middle of the T to accommodate the rib attachment. So, in my case, my long 10- foot base pipe was almost 11 feet long.

Square Structure Sizing
I used 1 inch PVC for the square structure. When shopping for your PVC pipe grab two different 10 foot long piece: 1-3/4 inch and 1-1 inch. You'll notice the 3/4 inch bends and drops and the 1 inch basically holds its form. It was the rigidity of the 1 inch that drove me in that direction for the square structure. If you are going to have any dimension in your structure greater than 10 feet, I'd recommend upgrading above the 1 inch. This will add weight and dollars to your project so you may want to keep it to 10 ft. or less.

Additionally, consider whether you want to hang baskets from square frame. If so, you can upgrade the PVC pipe above 1 inch, add vertical supports half way down the 10 foot pipe, or plan to run galvanized electrical metal tubing inside your PVC for greater stability.

Curvature and length of the ribs
I used 3/4 inch PVC for the ribs. This seemed just flexible enough to bend around the square 1 inch pipe frame while still solid enough for a reliable structure. The 1 inch pipe is firm enough to hold mostly square and not to bow while 3/4 inch pipe is bent around it. However, where the ribs meet the square structure is a stress point . You need the ribs to be about 2 feet longer than the height of the square structure. If they are less the square structure will bow and curve under the ribs.

Ribs spacing
Space your ribs at about 2 feet apart. This should give the proper amount of support when it is time to add the exterior sheeting. If you cut lengths of pipe at 2 ft and add T fittings the spacing will be a bit over 2 ft but, in the end, it will be fine.

PVC is not an exact science
I'd like to close the sizing section with the notion that PVC was not made for this kind of contruction. When you start to fit you pipes and fitting together variances will be introduced. One pipe inserts 3/4 of inch into the fitting but anoth 5/8 of an inch. A T fitting for a one inch pipe adds 2 inches of length but a T fittings for a 3/4 inch pipe add less. In the end the dimensions change and grow as you assemble no matter how well you plan. The good news is that PVC is flexible...You should be too!!!

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Sunday, January 31, 2010

PVC Greenhouse: Pipe Fittings

Plan your pipe fittings
I found it helpful to draw (and redraw) my proposed greenhouse. Only through this kind of visualization was I able to build my inventory list.

For this project you will need many different kinds of PVC pipe fitting. For my project it looked like

24 - 45 degree elbos 3/4 inch
4 - cross pipe fitting 3/4 inch
2 - T fittinggs 3/4 inch

24 - T fittings for 3/4 inch -1 inch
24 - 90 degree elbow 1 inch
4 - T fitting 1 inch

Remember that the T-pipe fittind along the base ahve to be "3/4 inch -1 inch T pipe fittings". This indicates that a 3/4 inch pvc pipe (the rib) will be joined to 1 inch PVC pipes (the base)

Buy a few more than you need of all sizes
They are cheap and it will allow for mistakes and adjustments along the way. Keep them in good shape and return the extras. T's are especiall helpful because you add a cross-support anywhere in your square structure where you want a bit more firmness.

Don't worry about the above counts. I will post a complete project manifest once my Greenhouse is complete

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Saturday, January 30, 2010

PVC Greenhouse: The Base

Okay, so enough talk. Let's build!

The Base
The base is 10' x 5' of 1'' pipe. My PVC came in 10 foot lengths so you can layout the base with just three pieces of pipe and cutting just one 10 foot pipe in half. After the 5' lengths are cut, layout the base on the ground Use elbow fitting at the corners if you want and get a feel for the size of your new greenhouse. Visualize the amount of space it will take up and whether you plants will fit. Its pretty big using my dimension so I hope you like it. (Building is half the fun so you could just make a second one if you need more space :)

Cutting for the ribs
The 10' lengths of pipe need to be fitted every two feet with a 1" - 3/4" inch T fitting. You need to make 4 cuts in the 10 foot lengths. I wanted the sides to be nice and even. You also want the sides to be even with the ridge beam pipe. (Ridge beam is a term for the center top most beam that wooden rafter attach to in home or barn construction.)

To keep things even, I duct taped the two 1" pipes and the one 3/4" ridge beam pipe together at various point and cut them at the same time I numbered them to keep things in order. (see images)

Reassemble the base with T-fittings
Insert a 1" to 3/4 " T pipe fitting in connecting the 5 pieces of 1" inch pipe and a T fitting on each end. You'll quickly notice that these length need to end in elbows and not T- fittings if the base is ever to reform as a square. I simple cut 1" of pipe off each end and used it as a connector between the elbows and the T. So what you end up with is E-T-T-T-T-T-T-E for each long side where E=elbow and T=T.

The short sides of the base

Take the two shorter 5 foot lengths of 1" pipe and tape them together. Cut 1 foot off of each end.
Connect each piece with 1" T. You can connect these lengths to the elbows on the 10 foot lengths and you base is loosely fitted together but basically complete.

Here is how it looks with the fittings

Ignore the Ridge Beam pole in the middle. I'll cover that next.

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Friday, January 29, 2010

PVC Greenhouse: Ridge Beam

Ridge Beam
Assembling the ridge beam (and rafters) was one of the most satisfying parts of this project.

The hard part:
Assembling the parts is rather straight forward. However, when it comes time to glue the parts together it is imperative that all the T's and the X's are on the same plane. In other words, the fully assembled ridge beam, together with the fittings, should rest flat when placed on a flat surface. This is key, because without the fitting laying flat on the same plane, one or more ribs, when attached, will be flying off too wide or tucked in too narrowly to be uniform. Don't worry. I provide tips down below to help gurantee your success.

Ridge Beam:
You begin with the 3/4" 10 foot pole which is now cut into 5 pieces. Add a 3/4" T on the end of part number 1 with the pole being the center of the T. Then connect part 1 to part 2 with a 3/4" cross fitting keeping the pole straight. Connect all the other parts with cross fittings. For the last piece, cap it with a T on the end like you did for part one. The result is something that is friction fit together and looks like this:

Now let's glue the part together.
PVC bonding glue looks and smells like rubber cement you use in crafts. DO NOT BE FOOLED. When used to assemble PVC pipe and fitting it very hard after 5 seconds and rock hard and virtually unmoveable in 10 seconds. Trying to undo a glued fitting will prabably crack the fitting. So when it is time to glue, be sure and be quick.
Glue the T fitting to part one by running the PVC glue brush around the inside of the fitting and the outside of the pole. Push the two together. This one is easy. Use it to practice and get a feel for gluing PVC. Use a wood block or a 10 inch piece of PVC pipe as a hammer to really force them togther. Don't slam too hard and don't hammer aginst your wooden deck unless you want a lot of round gouges in your deck surface. ( Also, don't use a real hammer, it will crack the PVC. )
So here is how you keep all the fitting aligned while gluing
1. You now have ththe T and pipe part 1 glued together...

2. And you want to add a cross like the image below BUT the T and and cross have to be perefctly flat on the same plane. So...

3. The strategy is called "make a square" strategy. You will connect additional pipes and crosses to the parts you will glue so that you can force them to be squarly aligned. (See image below.) All of the parts you add will just be friction fit. When you apply glue to the cross and the pipe you will have the leverage of the temporary pipe and fitings to force your glued parts into square. Your square could twist so placing it on a flat surface before the glue sets will help as well.

Repeat for Ridge Beam section 2 through 5 ending with a T fitting on the end of 5.

When you are done you will have this only it will be about 10' 6" long

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Thursday, January 28, 2010

PVC Greenhouse: Rafters

Adding the rafters is a pretty simple step. The rafters are 4" long 3/4" piece of pipe attached to the ridge beam fittings. Once complete you will have a center support structure that looks like the image to the left.

Let's get started.

Cut 12 four inch sections of 3/4" pipe. These are your 'rafters.' You can attach and glue these to the ridge beam fittings right down the line. Use a piece of wood or pipe to really set these in tight.

This task is complete when you add 45 degree pipe fittings to each rafter. The 45 degree fitting should be pointed downwards. See image below. This is front end view of the T fitting on the ridge beam.

It is really important that 45 degree fittings are all aligned correctly. When it is time to set these with glue I recommend using a 3/4" piece of pipe in the open end to gain leverage as you twist the 45 degree elbows on. This will give you a large handle rather than just grabbing the fitting. See image below

That's it. You're done. Here's an image of the ridge beam and rafters high above my very 'in progress" greenhouse. (Only 4 ribs were attached at this point which is why it appears a bit curvy)

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Saturday, September 23, 2006

PVC Greenhouse: Wrapping the greenhouse

So now you have the frame complete (except for the door which will come later). You are ready to wrap you greenhouse.

The supplies I used were:
- 1 - 20' x 25' - 4 mil plastic sheeting (note: this year I'm going for 5 mil)
- about 50 snapclamps (various sizes)

Snap clamps, pictured below, are these need litte device that are used to clamp tarp and plastic sheeting to pvc pipe.

So, before you unroll your huge plastic sheet makes sure you either have a non-windy day or a buddy. The thing will blow around and you'll never get that big thing onto you frame.

Open up your tarp. Take one edge and insert it under the greenhouse to the half point. Now take the tarp and roll it up one side of the green house, over the top and back down the other side.Tuck the edge under the greenhouse. Have the two edges meet in the middle under the greenhouse.

You now have the plastic sheeting forming a big tube around the greenhouse with plenty of slack on both ends. You can now attaching the plastic sheet to the rib poles using the correct sized snapclamps. You can place about 3 per rib. Start by the door, completing and entire pole on ight then left, and work your way back. Two important tips: First, if the tarp is too tight applying the snapclamps can tear the plastic. The tarp has to be loose enough that is can wrap around each rib then add the clamp. The second is that winter winds will put stress on you sheets where they meet the clamps. Consider adding a small patch of duct tape to the sheeting where it meets the clamp. (I have never done this but will for this winter)

Now, you have to wrap the end of the trap around the frame. This takes a bit of creativity but is like wrapping a giant birthday present where the tarp is wrapping paper. Standing outside the greenhouse, I took all the excess tarp from the right side and wrapped it around the rear until it met the the leftside. Now bring the left excess over to the right. make sure the trap is alway laying in such a way that rain will run off, and not into, the folds of your tarp. Secure the sheeting strategically with more snap clamps. Tuck the extra at the bottom under the greenhouse and also secure with snapclamps.

The method above gives you overlapping layers of plastic sheeting. Not as pretty as if you cut the sheet to fit perefctly but it lasted all winter and was quite air tight.

Take your time and you'll end up with something like this:

(Nice picture...right? truth is, that sheet is wrapped a bit to tight and did not leave enough slack around the snap clamps. I has plenty of tearing that year and learned to leave the sheeting a little more baggy)

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