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Greenhouse Plans

Posted by esobofh 7b (My Page) on
Tue, May 13, 08 at 17:20

Howdy Folks!

I'm planning to build a 12x20 greenhouse using ACQ treated lumber and Tufflite poly.

My neighbor works for a building wholesaler, and has priced the wood out (as shown in the plans) for $130.00 CAD.

Great deal I thought!

So before I start building, I was hoping to get some feedback and suggestions on my plans.

So please, take a look and let me know if you think it's a good plan, or destined for collapse!!! :)

Here is a link that might be useful: Flick


Follow-Up Postings:

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RE: Greenhouse Plans

The layout seems pretty standard. I dont see a problem there.
What are the dimensions of the wood that you are planning to use?
And how do you plan on connecting the wood together? (metal brackets, screws, etc).


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RE: Greenhouse Plans

Not good enough structurally. It will need cross bracing in all directions.

dcarch


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RE: Greenhouse Plans

esobofh,

Add a "knee wall" of 3/8in pressure treated ply. Mine is 2ft.

That will solve your cross bracing requirement on the walls.

Think about 14x20 instead, and a 30/60 degree roof pitch. Side walls of 6ft above the base. That way you really get the most out of 8ft lumber with virtually no waste.

Tuflite IV is a nice covering to work with.


Also as the lumber is cheap add some cross braces to the rafters, A foot long will do, up close to the top.

I would add one or two 4x4in beams across the greenhouse at the top of the wall height to stop the structure bowing out. I notice on your drawing they would be just above head height.

Have fun!


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RE: Greenhouse Plans

Wow.. thanks guys great feedback! I was just rushing out the door yesterday when I posted that, so I didn't give much info.

Here's some more details;

The GH is being built on the electrical utilities Right-of-Way, so it has a height restriction of 10'. This design comes in just under that with 5' side walls.

The base is made from 2x10 ACQ treated lumber, and the majority of the rest of the framing is 2x2. The framing is 2' on center (roof and walls). I had planned to build the end wall and front wall, covering them in poly, and then assembling the two sides, finishing with the roof.

My main concern is structural integrity - and also the flow from the roof to the walls where they meet. I'm kind of stumped on how to make that a smooth edge so the poly doesn't become 'ribbed' with the 2x2's on edge as shown in the drawing.

wetfeet; Was thinking just screwing with 2.5" deck screws - would you suggest anything else?

dcarch; What would you suggest for crossbracing - would diagonal 2x2 in the corners of each wall be sufficient?

Chris; I like the idea of a knee wall, and that would for sure brace it very strongly - but I don't want to limit the amount of light into the GH at all (i'm in Canada - Vancouver, BC).

Why do you suggest 14x20 over 12x20? The roof rafters are 30 deg. is that the same as 30/60? not sure what you mean there ;)

I like the idea of the beams across the GH width.. considered it added to the plans! :)


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RE: Greenhouse Plans

I've added a corner brace to the model.. would this work, or would you guys suggest something different?


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RE: Greenhouse Plans

Here you go. Minimum bracing needed.

dcarch


Photobucket - Video and Image Hosting


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RE: Greenhouse Plans

Fantastic!

Thanks dcarch - you figure 2x2s are find for bracing, or should a guy uses cable/turnbuckles?


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RE: Greenhouse Plans

If you do the math, with a 30/60 deg slope and a 14ft wide greenhouse then the rafters are about 8ft long....

less wasted wood.

As to a knee wall, well kneewall every side but the south one. Where you are I would also recommend a solid and insulated north wall, and even a solid and insulated north roof.

Here is a triangle calculator.

http://www.csgnetwork.com/righttricalc.html

For your enjoyment and inspiration, the following link is to a set of pictures of a real pressure treated 2x4 framed 24x14 greenhouse covered in, you guessed! Tufflite IV!

Here is a link that might be useful: A greenhouse....


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RE: Greenhouse Plans

Chris - that is fan-freakin-tastic!

A couple of questions;

It looks like you've stapled and strapped the poly to each framing member - how was that worked out with regards to expansion and contraction? Any rips at the location of the staples?

Getting to your kneewall, the poly looks flush, and the strapping over the poly appears to overlap the plywood without offset - was it notched to make it flush with the wall?

Overall, how do you like the performance? I plan to paint mine white too, what paint did you use? Any hindsight-insights you want to give to someone that appears to be going to down a very similar road? heh

What is the overall height of your greenhouse?

I'm considering your suggestion of 14x20, but I have a 10' height restriction due to a utility right-of-way (power lines) in this area.

thanks!!


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RE: Greenhouse Plans

One more thing...

Would you have considered building your greenhouse with 2x2s?


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RE: Greenhouse Plans

ok I lied.. one more thing ;)

How far apart are your 2x4s spaced?


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RE: Greenhouse Plans

""It looks like you've stapled and strapped the poly to each framing member - how was that worked out with regards to expansion and contraction? Any rips at the location of the staples? ""

Not to each framing member, The roof is just secured along the edges. The front is secured at the ends and the middle and the side walls are secured at each strut.

There are no rips at the staples because.......

1, Pull the poly tight and bang in a few staples.
2, Stick exterior duct tape on.
3, Go crazy with the staple gun!
4, take a 4ft length of non-pressure treated lath strip you painted with a couple of coats of latex paint.
5, do a squiggle of the cheapest latex caulking you can find.
6, Nail that over the top of the duct tape (only use one small nail per foot It is easier to get it all back off afrer 4 years when you change the poly!))

NEXT TIME!!!! I am going to install channels and wiggle wire. In the long term it is more cost effective.


Repeat steps 1 - 6 for the second layer of poly.

""Getting to your kneewall, the poly looks flush, and the strapping over the poly appears to overlap the plywood without offset - was it notched to make it flush with the wall?""

Because there are two layers with a 1 inch wide by 1/4 inch lath strip and caulking in between the top poly layer looks flush.

""Overall, how do you like the performance? I plan to paint mine white too, what paint did you use? Any hindsight-insights you want to give to someone that appears to be going to down a very similar road? heh""

I like what I built. I do not really use it as a greenhouse as you can see by the junk in there. However for a gardening purist it is technically a double layer poly covered greenhouse with an insulated north wall and part of the north roof.

I just used cheap exterior latex. You have to remember that even though the inside looks like it is inside because of the humidity and heat the conditions in there as far as paint goes is worse than being outside!

Paint the wood with a couple of coats of whatever before you build it!!!!!

Painting it all two or three times once built is a real pain.

""What is the overall height of your greenhouse? ""

I layed down an 8in high base of cement blocks on the existing base I had, the side walls are 6ft and using that calculator (It is dark outside I ain't going out there) the roof triangle bit is 4ft high.

So it is 10ft 8in tall...

""Would you have considered building your greenhouse with 2x2s?""

Yes I would consider it. Knowing what I know now my greenhouse is way over engineered. The plan was/is to extend it another 28ft. The extention would be a garage and workshop. If you look at what was there before I built the first part you can see what I am aiming for. That is why my greenhouse is so high. The completed building is the right height to insert a standard garage door.

Also that is why the ends of my greenhouse look different. The end with the door in it is "temporary" that is where the extention will be.

""How far apart are your 2x4s spaced?""

24 inches, the idea was to cover the greenhouse part in polycarbonate and the garage part in conventional sheeting and siding.

If I was to build a new greenhouse covered in a double layer of inflated poly I would seriously consider a 3ft or even 4ft spacing like you see in hoophouses.

After all we are just building a wood framed "hoop" house.


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RE: Greenhouse Plans

Thanks Chris!

I hadn't actually realized it was double-wall poly. Nice.

That makes sense now, seeing the outside layer flush with the plywood.

Thanks for taking the time to give a great detailed response - your helping me out more than you know!!


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