I Made A Different Sort of Cold Frame

Last year my cold frame was constructed out of bricks, with the cover made out of a plastic tarp.  It worked very well, though once outdoor temperatures reached sixty degrees, I had to be very careful with ventilating it.  A rectangle of unventilated bricks can quickly become a seedling oven. 

This year my brick pile is still frozen solid and the thought of trying to maneuver a wheelbarrow through a foot and a half of snow a few dozen times to transport the bricks to the patio was just not appealing.  So I decided to build a coldframe.  I tweaked the traditional coldframe design to give it a bit of my mutinous and somewhat risky style.  My husband calls it the tsunami frame.  More on that in a minute.

The cost to build this was cheap.  I spent about $20 on wood and $8 on a 50 foot, 4mm plastic tarp.  The staples and screws came from the husband's stash.  Building it was pretty easy.  I basically just built a frame and mitered a 25 degree angle to the uprights to make a slope to the roof.  Now that it is done, I wish I had made the slope a bit more to help shed water. I can still tweak it later to make the slope more extreme, but I'm going to try it this way first to see how it goes.

Once the frame was done, I wrapped each side with the tarp.  The plastic is stapled at the top, wrapped under the bottom board to help protect if from moisture and then stapled again to the top.  The two thicknesses of plastic with a 3" airspace in between them helps to insulate the frame.  I debated about filling that space with bubble wrap but wanted to keep costs down so left it like this.  All except for the back wall...

The back wall I added two thicknesses of black garbage bags between the plastic tarp walls to help the back wall collect heat.  Then I filled the garbage bags with water.  Yep, the back of my coldframe is a wall of water.  The water doesn't quite go to the top, because I got nervous about the staples ripping through the plastic due to the weight.  It goes pretty high though and my hope is that it will collect heat during the day and help keep temperatures moderate at night.  It will definitely assure that this thing doesn't blow over.  Now chance of that.  It's heavy.  I've stapled the plastic in such a way that if the staples give, it should be the outer wall that fails.  Thus any potential tsunami's are more likely to dampen the dog than the plants.  I hope it doesn't give though.  I'm quite proud of it!