How to Build a Greenhouse Using Plastic Bottles
How to Make a Plastic Bottle Greenhouse
Here is a step-by-step guide for building a plastic bottle greenhouse for those of you with the time and patience to collect enough empty plastic bottles to construct one.
Making this type of greenhouse is relatively cheap and easy, but it is also a bit of an undertaking in terms of labour and time, especially if you've never done anything like it before. It does make a great project for a large group or community or school organisation, but you can do this on your own, too. There is no reason why everyone should not have a wonderful PET plastic construction in their yard.
How to Build a Plastic Bottle Greenhouse
- Remove and recycle the lids.
- Wash and remove the labels from the bottles (not necessary, but it ends up looking nicer).
- Use scissors to cut off the bottom of each bottle.
- Plan your sizing. I recommend two 6' long walls facing two 8' long walls. 7' or 7.5" high should suffice.
- Fix four posts into the ground. These will be the corners of the greenhouse. Treated 4” x 4” or 2" x 2" posts cemented into the ground works great. All the PET greenhouses I have seen have had a wooden frames, which is not terribly "green" since trees will be sacrificed. You could use recycled lumber or metal pipe, but I am still trying to think of other, greener alternatives.
- Next, build frames for three of your walls: the two long ones and one of the short ones. (The other short wall will contain your door: See those instructions below.) Treated 2” x 2” lumber with mitred corners screwed together should do the trick. Lay them on the ground for steps #7- 9.
- Select and cut your material to string the bottles onto and use as the sides of the structure. This can be bamboo canes, dowels, lengths of stick, or wire— but whatever you choose, it needs to be slim enough to feed through the bottle openings and long enough to span from the ground to the top of the wall frame.
- Thread the bottles through whatever material you choose to use to hold them in a line. The plastic bottles will fit into each other and interlock.
- Then nail each cane or stick to the top and bottom of the frame.
- Nail this frame—now full of plastic columns—to the posts you set in step #5.
- For the roof, construct a simple gable frame (no eaves necessary) with 2" by 2" lumber. Screw triangular gables to your posts and use vertical supports to support the top of the triangles. Then lay a beam vertically to connect the two triangular gables. The sloped sides of the roof can be filled with plastic columns the same way you made the walls.
What Kind of Plastic is PET?
PET stands for polyethylene terephthalate, which is the type of plastic approved worldwide for bottles used for drinks.
Don't Forget Your Door!
- I suggest putting the door on one of the shorter walls. So if your structure is 6' by 8, use one of the 6' walls for the door.
- Connect the two posts you set in step #5 above with a vertical beam, then build two frames to fill that section instead of the one you used to create the other walls. Each frame will be approximately 3' wide, but factor in some room for movement.
- After you've attached the columns of plastic bottles to each frame, nail one to the structure and affix hinges to the other one and attach it to the post.
- Don't forget to measure carefully and make your door smaller than the inside of the frame to let it to move freely... even if it eventually warps or sags a bit.
Advantages of a Plastic Bottle Greenhouse
- It's cheap to construct. You will need approximately 1400 empty 2 litre (40 oz) plastic bottles to build a greenhouse that is 8' x 6'. If you don't have enough bottles saved up, you can collect them from neighbours, friends, hotels, bars, and restaurants in your area.
- It holds heat and keeps seedlings warm. The temperature inside this greenhouse will be about 10°C higher than the weather outside. That is a huge difference, and it should certainly lengthen the growing season for many plants, no matter what climate you live in.
- It is self-watering. Because there are gaps between the bottles, heavy rain can certainly penetrate into the structure. This is a huge time-saver for greenhouse growers. Also, rainwater is always better for your plants than tap water.
- It saves yet more plastic waste from the landfill. It goes without saying that if everyone saved those plastic PET bottles for constructions like greenhouses, there would be less plastic cluttering up landfill sites.
- It is cheap and easy to repair. You can simply replace any plastic bottle that has broken or been damaged. All the bottles are hooked onto either wire or a cane or sticks, so all you need to do is unhook the line, slide out the bottle, and replace it with a newer one.
- It is sturdy and can withstand strong winds. Plastic bottles can't get blown away when they are pinned into place. The strength of your structure will depend entirely on how well the lines of bottles are anchored.
How Many Plastic Bottles Will You Need to Build a Greenhouse?
You will need approximately 1400 empty 2 litre (40 oz) plastic bottles to build a greenhouse that is 8' x 6'.
How Should You Attach the Columns of Plastic Bottles to the Frame?
Use a U shaped nail or staple or fence stapling wire that is wide enough to accommodate the wire, dowel, or canes you're using.
Can You Make This Greenhouse Without the Dowels or Canes?
Another way to build your greenhouse would be to interlock all the plastic bottles together, one on top of the other, but without a dowel or cane as central support. Then wires can be strung both inside and outside the greenhouse to hold the bottles in position, as shown in the photo below.
You will note that, in this project, the lids were left on the bottles. There was no need to remove them, as nothing was being threaded up through the bottles. I must admit I quite like this idea as it means one less place for insects to enter and make themselves at home.
Using Plastic Bubble Wrap as Insulation
Plastic bottle greenhouses can also be insulated to keep out cold draughts and protect from rain. Recycled bits of bubble wrap do the job really well.
How Long Will This Type of Construction Last?
In Europe, building plastic bottle greenhouses has become a popular pastime for many. The plastic bottles stand up well under a hot sun, but they will degrade eventually. When it does, however, it's not hard to unpin the stack of old, degraded bottles and replace them with newer ones.