Constructing greenhouse basis
I am planning on getting a small greenhouse round 6x8ft however I am confused on the muse half. There’s numerous conflicting data so I simply needed to verify I am doing issues proper. I plan to dig out round 8″ deep, lay down geotextile material, fill in with some kind of coarse stone, degree, Make a body out of 4x4s with rebar going via to anchor into the bottom, after which connect the greenhouse to that. I am nonetheless not sure on the bottom stone part- ideally I might like to purchase in bulk however the one native choices I’ve are decomposed granite, concrete washout, limestone base, pea gravel, and another sorts of ornamental coarse stone. What ought to I be utilizing? It is about $100-$200 dearer if I had been to purchase paver base steps 1 and a pair of from residence Depot, however is that the higher choice? Is that this overkill? I am on clay soil close to the coast so we get tropical storms yearly and hurricanes now and again. Ought to I even be doing this lol? Would I be higher off hiring knowledgeable or is that this doable for somebody barely helpful? Additionally… Is stone even needed? Ive seen some folks simply degree the bottom and construct the picket body half or use cinderblocks, how needed is digging issues out and filling with stone? Sorry for all of the questions and thanks for any assist.
Additionally on a aspect notice, I noticed one individual say it is best to have round 3-4ft clearance across the greenhouse, however I deliberate to have it backed as much as a fence. Will this trigger points?
Comments ( 25 )
If the greenhouse is a kit, the manufacturer should have recommendations regarding foundations/bases. For many, the warranty is void if you don’t have what they consider a proper base.
We did an 11×11 frame for a 10×10 shed. We rented a rototiller to break up the surface, framed and “leveled” down about 6″ (treated 2×4 and we left a slight grade away from the property to direct water flow), laid pea gravel, then rented a compactor from Home Depot and pounded that shit like a Vegas hooker. Small shim to level the structure to offset the water control grade and then finished
Did in about a weekend and has held up against everything for about 2 years now.
I hope this offers any help. I’m just a DIY hobbiest, so I thought I could assuage any over-thinking issues.
We have a 10×12 Grandio and live when it can get pretty windy. Our lawn slopes so we hand dug down about 30″ (felt like 30 feet) on the high side to get to grade, built a rebar reinforced footer to support a cinder block foundation. Attached a sill plate with j hooks (just like a house on a slab) and bolted the bottom frame to the sill. We put french drains in around the base of the foundation, covered with gravel and fill. This was a pretty big job, I ended up buying a cheap cement mixer. If you are worried about finding your greenhouse in the neighbors yard after a storm, this is a good way to go.
I think if it were mine, I would use Concrete Deck Blocks as footings (3 on either side?). Burry them down to the slots and level them with each other. Your base lumber can fit in the channels and you can anchor them to the blocks to help with wind resistance. For the base/backfill rock, I would pick something “clean” or “free draining” to make sure it doesn’t hold moisture against your lumber
Just a note, depending on where you are (and it sound’s like this is you) the most significant force may be uplift. When we did ours, that was the biggest liability – keeping the greenhouse attached to the ground in the event of high winds. If a tropical storm is rolling through, a greenhouse isn’t that different from a big kite.
I know a lot of people just plunk it on the ground like any ol’ shed, but it’s worth consideration about how to properly fasten it to the ground so it doesn’t end up in a tree or the neighbor’s yard.
I will come back to this with the solution for you, just about to head out on a drive now.
What’s the size of the greenhouse, and what do you plan on growing in it?
Also, please link to the kit itself.
Have you looked at landscaping shops for aggregate options? There are often suppliers that can deliver a cubic yard or however much you need.
>Also on a side note, I saw one person say it’s best to have around 3-4ft clearance around the greenhouse, but I planned to have it backed up to a fence. Will this cause issues?
Probably, check with zoning usually you can’t have any structures a certain amount of feet from the property line.
IDK what your budget/how permanent you want the greenhouse to be, but if it was me I’d just lay a slab down and put the greenhouse on top of it.
I built a steel greenhouse for my mom. As a foundation I used hollow concrete bricks and filled them with rebar and concrete to form a solid rectangle about 3x4m.
I’d use concrete foundation blocks and 4×4 or 4×6 beams to hold it off the ground
Look into perma- columns. It’s prefab concrete posts that you can use as footers that are 3x better than standard.
I just installed a 6’ x 6’ Palram hybrid greenhouse kit. Im on fairly level ground. I made my foundation from pressure treated 6×6’s. I drilled 3 or 4 pilot holes on each length and drove 3 foot lengths of rebar in to anchor to the ground. I thought about the extra effort to dig down to lay gravel, maybe extending the life of the wood but I’m thinking I’ll get more than enough years out of them with out. I also like the extra 6 inches of height it adds to the building. I don`t have worry about hitting my head coming through the doorway.
https://ibb.co/MSW2rRH
https://ibb.co/8mTpYGH
I also cleared the inside of what ever grass’s were there, raked it level and set patio blocks that I had around for the floor.
>how necessary is digging things out and filling with stone?
So, you could just throw the greenhouse down on uneven grass.
The reason you probably don’t want to do that is that it won’t hold up for very long, as all the pressures of stepping on it and wind and weather will add stress to the framework.
You basically have to decide how long you want this to last for (is it an heirloom greenhouse you want to last centuries? You could go full-scale and build a foundation suitable for a house) and the trade-offs for how much time, money and labor you want to put in.
One thing you could consider is building a square outline of a foundation (say, about a foot of width), instead of digging out the full square underneath the structure.
The digging and gravel will give you drainage, which will help prevent movement from frost.
Something to elevate the shed off the ground (like your 4x4s) will keep it from sitting on damp soil and will help the floor last longer.
Your rebar will keep the shed from moving off its base with strong winds, or just movement over time.
>What should I be using?
I got my gravel for setting up a shed foundation from the same place that sells me mulch. I just called and asked for their recommendation.
>Would I be better off hiring a professional or is this doable for someone slightly handy?
The plan you’ve laid out is doable for someone handy, just a lot of manual labor. The one big thing you need to figure out is how you’re installing that rebar. I can just picture a gravel-filled hole with 4x4s on top, looking at the rebar, and thinking…. “shit”. You’ll probably want to put the rebar in place, then pour the gravel in.
The only other thing I haven’t seen you mention is a tamper. It’s just a big square of metal with a long wooden handle on it. You use that to compress the soil before putting down the landscaping fabric, then again every wheelbarrow load to tamp down the gravel.
Were you pricing out bulk stone options from Home Depot/etc, or actual landscape supply places? I would be shocked if you can’t get #57 stone or something delivered at a reasonable price (this is what we used in our greenhouse)
full project writeup here:
We opted to go below ground for slightly more temperature stability and additional interior height (instead of building a kneewall above ground and catching more wind exposure and looking odd unless we did nice-looking brick work or something
And to add, if you create a foundation, your local officials may have something to say about it. Since it has a foundation it becomes a structure and goes into a whole potential process of permits and regulations because it could be considered a permanent structure.
Decomposed granite is a great choice, it compacts down real nice and hard without too much effort. Kinda a pain to shovel though.
What sort of frost heave are you expecting though? If that’s an issue you might wanna overbuild the foundation say with deep concrete. Could do a few corner/side cylinders and set the greenhouse on those.
I got a greenhouse about the same size, similar ground. I made it easy for myself. Dug an 4 inch deep trench around the base and filled it with aggregate. Put some light concrete blocks on that and mortared them together and finish them with mortar. Then I anchored the base of the greenhouse to that foundation.
Don’t get hurricanes here but have had some strong storms here and it’s still standing.
I recently build a greenhouse myself, as the base I first mowed the grass totally down to the earth, afterwards i placed a lining on top and then (for my 3x5m area) around half a ton of gravel. That smoothed out everything on the ground and afterwards I could build on top.
Only works if you want your greenhouse to use pots only tho.
I would go with a concrete pier foundation- gets away from HOA slab issues, is easy to do if you rent an auger for the pier holes and you can mix the concrete yourself and use concrete forms for a clean look. Here’s a video I just found that discusses it! You get benefits of Slab foundation but it’s easier to DIY and if ever needed to remove.
I just wanted to add that mine has held up really well for years now and that the “panes” are held in place by clips which also worked really well. But some friends of mine up in the hills mentioned that the three they bought of the same model, flew apart in strong winds. I couldn’t afford to have the happen to the contents, so I bought window caulking sealant and sealed all of the panels into place. Yes, it canceled the warranty. But I doubted that I would ever be asking for said warranty to be honored anyway. And for shelves, I bought the plastic kind you find in hardware stores that are very easy to assemble and won’t rust or warp from getting wet. I was able to fit 7 of them into it.
I’ve got one of the harbor freight ones that size and it’s bolted on a frame of 4x4s, resting on a foundation of pavers laid tight. Mine is also about a foot maybe less away from a fence to the back, and 3′ or so away from my garage to the front of it.
Sidenote if you’re planning on starting seeds in there you *will* need a shade cloth, id recommend greenhouse megastore for one
I did this last year, also a 6×8 about 3 – 4 feet from my fence. I’ve got clay soil also. I used 6×6 pressure treated directly on the ground. 2′ rebar through it. I then screw the greenhouse kit to the 6×6 framing, pretty much every hole it had. I also installed brackets on the inside corners. Landscape fabric and gravel inside. I put rectangular stones down the center that I bought at at a local stoneyard.
You should get the greenhouse before doing any foundation work. They have different requirements and different setups for how they are installed. Mine had a large U-channel metal base and if I had done what I though I needed to do before buying it, I would have wasted a lot of time, money, and energy and on top of that, the whole greenhouse would have been 6 inches too high, and the door frame would have been a step over tripping hazard. I was basically thinking what you were thinking of building a base with posts into the ground but none of that was needed.
Keep in mind this isn’t a house or barn and it doesn’t need the same kind of planning for the foundation.
I believe the point is to dig your foundation below the frost line so you don’t get frost heave.
You can also consider mobile home anchors and strapping. They screw into the ground and then you fasten the strapping from the anchor to the frame. Simple, strong, relatively inexpensive and fast.