cold frame project 2007 & 2008

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Blog entry by oldretiredjim posted 11-15-2011 12:12 AM 1751 reads 0 times favorited 0 comments Add to Favorites Watch

Here is another project that is basically wood. My cold frames.
As with everything I do light is better. I have my raised beds built with old redwood decking. I don’t know how old the wood was when I bought the house but the beds have been in use since 2005 and there is not much sign of rotting. Anyway, on to the project.
Like many living on fixed income in northern areas feeding the family will include a garden. Given the climate this means protecting plants in the winter. If you have read my blog you will see that I have a real liking for T&G cedar siding. Easy to come by, easy on equipment, weather resistant, and light.
I had a plan sort of which included a T&G back, Plexiglas side, top made of cedar strips and greenhouse polycarbonate. The top is very lightweight and strong. All my beds are 3’ dimensions and by going with a 3 X 6 I could cover the thing with a single piece of polycarbonate from HD.

4 pieces of 1 X 6 T&G gave me a 20” back. The back joints of the sides were overlap and the angle in the front was a butt connection secured with a plywood gusset.

The gusset is visible in the left front corner. The polycarbonate panel fits perfectly with 2 cuts. The stuff isn’t that easy to work with so i had to clamp each side of the cut to minimize the vibrations and potential splitting. And the full sheet wants to flop around and break. However with a little care I was able to make clean cuts with my Hilti skill saw. Love that tool.

I fabricated 2 cross braces, one for each seam and to add rigidity i used the readily available molding strips under the ends and screwed every ridge. For the cross braces I cut an initial angle on the table saw and then worked it to where it fit with a hand plane. I caulked the seams but i am not sure that is necessary.

I painted the insides white for reflective purposes and stained the outside to match the shop. One cold frame had a heat trap made of PVC. I filled it with 50% water and 50% propylene glycol. Visible in the second photo. I tore it out this year because I couldn’t see where it made much difference. When the temp hits the low teens and single digits the cold frame freezes. Nothing grows here in December and January without heat and that is not the point.

I hinged them both the same so the covers are interchangeable. I can put chicken wire covers on in the summer to keep the chickens out.

The first unit has been in use for 5 years and worked so well I built a second unit a year later. These things work.

The whole system was pretty simple and here in Salt Lake we can eat fresh greens from late January until the main garden is ready. I keep plans of ost of the things I do and in this case it came in handy for building the second unit.

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