Relieving some sleet-induced stress

After our recent day of ice and sleet, of course everything was covered in it and I've posted plenty of photos of the plants that were iced. I don't suppose I need to post a photo of a snow and ice-packed driveway, as pretty much everybody either knows what that's like, or lives somewhere where they never have to care. What I didn't post about is my temporary greenhouse. You know, the one that's built from PVC pipes and plastic sheeting.

I know what you're thinking. You're thinking "PVC and plastic sheeting -- that sounds strong!" Then of course you start laughing. Well I'm happy to report that the greenhouse was stronger than expected, and the other day I removed the 2" of ice and sleet from its roof.


From a distance it doesn't look bad, which is the reason that I didn't come out here sooner after the storm, or even while the sleet was falling.

Up close you can see the roof is sagging quite a bit though, and the plastic was pulled very tight:

Normally pretty flat.

Once I started pulling off chunks of ice, it was easy to see why:

This stuff may not look super thick, but it is very dense and quite heavy. How heavy? It would have been nice to be able to cut a one square foot piece of this and weigh it inside, but I'll have to settle with an estimate...

I picked up some big chunks that were maybe 2' x 2', and they weighed at least 10 lbs. I'll just call it 10, which makes it 2.5 lbs per square foot (10 / 4 = 2.5). Since the roof is about 8' x 10' (or is it larger? I can't remember) that means that there was at least 200 lbs of weight on this plastic structure. It could have been more than this, as I think my estimate was on the low side. That's still a lot more weight than I suspected it would hold!

With the ice removed, the roof looks fine -- except for the center metal pole, which now has a nice curve to it.

Inside the greenhouse things look normal:

Not surprisingly, some of the magnets that I'm using to clamp a roof flap closed fell off when I slid off the ice. (I used one magnet outside and another stuck to it inside.) A couple of them were easy to find inside as they were out in the open on the ground, but a couple others are "gone".

I'll probably find them in the spring when I drag the pots outside again. I'm guessing they're gone for good though.

Now that I've seen how the roof behaves under load, I'm going to keep a closer eye on it during the next snowfall. I may have to clean it off before the snow stops falling, and will definitely have to make some "adjustments" when it starts warming up and we get more rain -- mainly in the form of drainage holes where the water starts pooling.

But now I'm really thinking about how nice it will be when it's warm enough to pull these plants out of here... but that's at least 4 weeks away from now... wait, 4 weeks? Wow, only 4 weeks! I just felt my spring fever click up a notch or two.

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TC  – (February 6, 2011 at 11:53 AM)  

Looks like the greenhouse held up fine. That's good strength for a flat top design. Very clever with the magnets. I'm starting to worry about mine. A little too much snow on top. We are getting pounded this winter. I finally started my own blog with a little inspiration after following yours over the last couple weeks. Feel free to check it out and leave a comment.

JiffyJ  – (February 6, 2011 at 3:51 PM)  

This winter I have been eyeballing my small garden and trying to design a greenhouse to grow some winter veggies. We got one good snow this year that lasted (in the shade) about 5 days is all.
Thank you for posting your progress on your greenhouse. Looks like I have something to copy. :)

Gerhard Bock (Succulents and More)  – (February 6, 2011 at 4:30 PM)  

Great photos. I was amazed to read that the plastic roof was able to carry that much weight.

:: Bamboo and More ::

Steve Lau  – (February 6, 2011 at 7:30 PM)  

I've had at most probably 20 inches of snow on my greenhouse at any one time, but it tends to either blow off or melt and slide down after a few days so I never bother to mess with it.

It still did get brutally cold on the -9F night when it got down to near 17F which is pretty cold especially for pots that are just sitting on the ground inside the greenhouse. Surprisingly the only thing in the greenhouse that is getting burned are generally the 1st year moso seedlings.

Based on my experience with greenhouses, I'm assuming that if I did build a poly-tunnel right over one of my prized groves, it would keep it green all winter long.

I usually let the snow stay on top of it to try and provide a bit of insulation.

GrowingHabit –   – (February 7, 2011 at 6:27 PM)  

Have you considered the hoophouse shape as an alternate? Quick and utterly simple to put up, and loads just slide off.

Still just can't believe the plastic took that much weight, let alone the PVC...

TC  – (February 7, 2011 at 6:40 PM)  

My greenhouse collapsed today. Bummer. I didn't have all that much in it but now I am out a greenhouse for next spring. I'll post some pics on my blog tommorow if you want to see the carnage.

Alan  – (February 8, 2011 at 9:45 AM)  

GrowingHabit -- I did, but when I first built this two years ago I didn't think I had the room for hoops -- it seemed like only larger designs used hoops, as there is a certain ratio of length to width/height that's needed to give them stability.

TC -- that's too bad about the collapse. Snow loading?

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