Reclaiming an old greenhouse

Good morning,

I bought a small farm and moved into the mountains of northern Maine, and since 2019 my biggest feat has been humbling myself by realizing just how ignorant I am of the knowledge it takes to be a true steward to this land! That being said, I have finally set out to tackle reclaiming the two A frame greenhouses I have on the property (neglecting the other things that are falling apart).

The structures were overgrown but I’ve freed them from their confines and want to move them back about 50 feet. Their orientation (ends face north/south) will not change. I need to reapply the plastic sheathing which I located a roll of 4-6 mil plastic I believe was intended for the greenhouses. (Side note the owner passed away well into his 80’s, he certainly did a lot around here when he was here, but the property was neglected during the sale period, but some goodies were mixed in with all the garbage left in the barns)

The original building was set on concrete blocks and elevated and covered, and some 12”x8’ osb was placed upright along the bottom in what I assume was an attempt to block elements from coming in. I have a great view, at the cost of near constant wind. They say people from this town all lean to compensate for the wind pushing on them all day. Anyway… my questions as I undertake this:

1. I want to use the structure to protect more sensitive plants from the drastic temperature swings we have. It is not unusual to be 80 at 6pm and 40 at 3am. Only potted plants or raised beds will be kept under the cover. I have manufactured sand on site left over from installing a well line and plan on spreading about a 1-2” layer over the sod so I don’t have to mow nor worry about unwanted weeds growing inside. In addition I am putting down some fabric cloth to discourage vegetation trying to come up through the sand. Are there any benefits to allowing the grass to grow inside instead? Is there an alternative minimal maintenance floor idea I can use instead?

2.  When I reapply the plastic, do I leave the bottom 10” or so (2 cinder blocks) open as a vent all around? Or should I be pulling the plastic down to the ground? I think I am going to hinge a frame with plastic onto the A so I can potentially prop it open for ventilation. Is having a “window” to open worth the effort and do I need to sheath to the grass?

I’m attaching some photos that show the structure now that it’s been mowed and visible. It’s not large. Perhaps 4x8 each. Any further thoughts on what can be done is appreciated.

Hi! I'm very happy with my greenhouse, though it is a very different type from the ones you are talking about.

I would highly recommend that you get Eliot Coleman's books, especially the earlier one, Four Season Harvest.  He harvests fresh vegetables all year round in Maine, and has leaned a lot about what works or doesn't. The book was incredibly inspiring to me, and now I also eat my homegrown vegetables of one kind or another throughout the year, including during pond-hockey season.

Overheating in spring, summer and fall is a real problem, so yes, definitely make it possible to open them up or even remove the glazing for the summer. A single sunny day in an inadequately opened greenhouse or coldframe can kill your plants. 10 inches along the bottom will not be adequate.

I've heard so many people curse the previous owners of their land who had laid down landscape fabric or weed barrier or whatever it may be called, that I would strongly recommend against that. Roots will sneak down through it and when somebody wants to either remove that membrane or remove the plants above it, there will be an extremely tough tangle that breaks into plastic shreds when they try to pull it out.

I'm not sure laying the sand in a 1 to 2 inch layer over the grass is a really useful idea. Wouldn't grass grow right up through 2 inches of sand, and you've just raised your soil level? Sand is a good ingredient in potting soil, if you're intending to grow in containers, or start your own seeds. If I were you I'd save the sand for such purposes, and mulch areas you don't want anything to grow on with wood chips or unseedy yard waste or really anything.

I can't tell the scale from the photos. They look smaller to me but you seem to mention them being 8x4 feet? If they are very low and you have to crouch inside, why make raised beds inside? Ground level seems better. It would give you more room to move, more vertical space for plants to grow, and keep the beds more protected from the air temperature extremes, more protected by the ground temperature, which is more stable.

I suspect they are relatively short in height.  Consider a foundation, at the cost of mobility, to raise them so you can more easily walk into them.

Thanks for the quick response Rebecca! I will definitely look into Eliot Coleman, sounds like a fantastic resource.

The manufactured sand is crushed granite so I imagined it would block out anything, but I do like the mulching idea, and can easily make that happen (and happily to not move the sand). Mulch never even crossed my mind and I can mulch the sides as well.

You are correct that the a frames are very low. And I wrote raised beds, but we are on the same page that they would be ground beds that are not elevated. I don’t mind crouching lol. The structure is maybe 4’ tall + any blocks I use to elevate it, so the removable/hinged plastic would allow me to access the plants from the side without crawling around in it. From what you are saying, I think I will opt for something I can remove in sections and adjust for temp and airflow as needed. This will let me leave the frame up over the summer and reinstall when fall comes 2 weeks later (zone 4b, on the border with 4a/3b)

John I think I would like to put down the blocks and form a small foundation. Mobility is not a requirement for me, but I want to open up the sides (kinda like a hatchback) on both sides so I can just do whatever needs to be done from the sides and not have to walk into it. Rebeccas suggestion about putting mulch down is great because I don’t want vegetation I would have to maintain on the ground. I’m hoping to get the first one set, and will most likely set those cinder blocks in a connected square to rest the structure on for the elevation. Originally they had two blocks on 4 corners.
My daughter made it clear to me that a limpy duckling needs to be monitored and kept alive so I am splitting my focus between the two. Don’t wanna upset the 5 year old…
I’ll post more pictures as the project progresses.