I might suggest you not screw the roofing material (this material is clear?) on but perhaps just set a couple of bricks or rocks on it. When spring comes you need to have access to seedlings & remove cover in daytime yet cover at night time. If screwed in, that might be hard to keep covering & uncovering. I have read where people use clear plastic too for covering. Might be cheaper as Walmart sells it for like $6 & it's a HUGE roll! It's back in the painting dept.

Why bottomless? What will hold the dirt in? Do you plan to just use cups set inside you frame?

Bricks are a good idea, thanks. The corrugated plastic roofing material is clear and can be used for making cold frames (my dad has some). It holds its shape as it's a solid sheet. I thought about clear plastic (like a shower curtain) but I didn't like the idea of run-off from thawing snow pooling in one or two areas. At least with the plastic sheeting I can drill holes and there's less of a chance of snow melting in one place.

And I would use Solo cups underneath with holes drilled into the bottom so there would be drainage onto the patio.

Here is a link that might be useful: Example of plastic roofing

i wonder if you could put hinges on one end so you can just prop it open when need be?

My only suggestion would be to invest in some of that moulding that's shaped like the corrugated roofing, to nail to the ends of your wooden box. The roofing can crack pretty easily, and using this stuff keeps a lot of the strain off it.

That actually is a good idea with the sheet of plastic roofing. Light will get to the plants well, and the material is hardier than you would think. I found a site that talks more about these sheets. Some of what I read though was kind of off a bit, but overall, it describes them well.

Here is a link that might be useful: plastic roofing

What a great idea! If you can make the cover removable, you can use the box for something else. If you can make a box with hinges, it would all fold flat for storage.

I was just looking at that plastic corrugated roofing. It is nice stuff. Not sure about putting bricks on it. But that would be a quick start.

Maybe you can slant the roof and catch the runoff in something for later use.

Lots to think about. Thanks again for the great idea.

Basically what you are planning to build is a simple cold frame. You may find a lot of useful info if you research building and/or using a cold frame or starting seeds in a cold frame. You will most likely find most of the info targeted to growing vegetables but not all.

Good Gardening, Mary