Have you checked the Greenhouse forum?

Here is a link that might be useful: Greenhouse forum

Montane, I built a lean-to greenhouse against the garage at a rented home.

The greenhouse was built as 4 separate panels - roof, front wall, and 2 side walls. Used storm windows and a storm door were important parts.

The roof was the largest panel and was a wood frame covered by transparent, corrugated fiberglass. The south side was essentially a short framed wall covered by plywood siding on the lower part. Storm windows fit within frames above this. A bench inside was at the height of this short, insulated wall. The plants sitting on this bench were directly behind the windows. And, this bench was screwed to the walls and helped hold the entire thing together.

Of course, the end walls were rather oddly-shaped polygons since they supported the sloping roof while providing frames for another window in one wall and the storm door in the other. The end wall window was the only one that was hinged and could be opened. Cross ventilation was gained by propping open the door.

I built the greenhouse panels on my concrete driveway and assembled them on a few concrete blocks beside the garage. The end walls and roof were attached to the garage with a few lag screws.

These walls and the roof were held together by bolts. After dismantling, everything was stacked into a pickup and moved to my present home about 12 years ago.

There, my garage didn't have a wall facing the right direction so I had to build one. That's right - just a wall springing-up in the middle of my backyard. It served as a new north wall for the lean-to. The wall is still there but the lean-to was replaced by a larger greenhouse/sunshed after a few years.

All this is doable and it just takes a pencil and some graph paper to figure out how to assemble the structure. It may be best to use four 4" by 4" posts to serve as the corners. I didn't do that - the corners of my lean-to were a bit complex because they had to fit together.

Best of luck,

Steve

I'm designing my future greenhouse in large part on sliding glass doors. You can get the individual doors for quite cheap usually, used, and it's just a matter of 2x4 framing around and attaching the doors to the simple frames.

Haven't figured what to use for the roof yet, though, and expect that might be the more expensive part of the whole project.

where do you get used sliding doors?

I'm expanding a lean-to greenhouse built by my contractor ten years ago - the roof is old shower doors. But he never told me how to score them for myself.

Try a Habitat Restore store for old shower doors and glass windows. But I'd be careful of what glass is used for the roof regarding weather. A lean to would be much easier to build.