Buying a 2k sqft greenhouse

Im looking to buy a property with a greenhouse already on it. the greenhouse needs some work but it seems like a way easier route then building from scratch.

ill need to add more vents and put a vapor barrier down. it was dug into the ground so you walk in the door and go down 3 steps. down about 3-4 feet. problem is the water table is kind of high in the area. it has a sump pump in the middle of the floor sunk down another 2-3 ft. I plan on using at least a couple quest dehumids and 2 bad ass greenhouse heaters at the end. does that sound like enough or is the humidity still going to cause me problems when the place is full in October?

I was originally planning on growing in 4x4x2 planter boxes and letting the roots go whereever under the boxes but if my water table is only 2-4 ft below the boxes will that stay to moist. will I just water less?

thanks for any input

It's gonna get humid, might need 4 if u want to be sealed. Definitely worth it to hit that good vpd.

Fill up the tub and float foam on top for deep water culture. One big hydro greeny.

there is not much you can do about the water table issue after the fact... best way to deal with it now would be to put down something like a high flow composite drainage mat ( google carlisle drainage composite or mapei drainage composite.

OR

geotextile layer > coarse compactable fill with high permeability and high pore spac > geotextile layer.


after that you would then build up a level base from a highly compactible and decently permeable fill materal like decomposed granite that would also allow for drainage into this high flow sump drain system.

in either case, you would grade into a proper sump pump having enough vault space to allow your pumps to run for minutes at a time not seconds.

both of those are very expensive options though, especially at 2,000 square feet ( drainage composite is literally like 5 bucks a square foot)... and you could probably just install an EXTERIOR french drain with a new sump pit outside for like half the cost.

problem with the french drain is then you need heavy excavation yadda yadda, i could talk all day about the tradeoffs between waterproofing systems,

but basically you either need a means to convey the water once its inside, or a means to intercept the water before it enters the greenhouse.

regarding dehumidifying your greenhouse? why fuck with that monsterous problem when you already have an issue with ground water?

honestly i think trying to tackle both at the same time is begging for dissapointment... maby run a few seasons in what you are proposing to run right now, with just forced air circualtion and supplemental lighting etc, what ever you need... eventually i think you would get a handle on what issues need to be addressed ( managing the ground water), by just observing humidity inside the space after rain and throughout dry and wet seasons.

Stay Gel^N 247 said:

Fill up the tub and float foam on top for deep water culture. One big hydro greeny.

Click to expand...

oy... good luck with that.

i just worked on an elevated pool for some fancy hotel... the waterproofing is monstrously complicated when working ontop of geofoam(engineered styrofoam for ultralight weight fill).

the reason why a regular gunite pool is waterproof is becase the rebar schedule and grade beam is able to keep the cracks smaller than the water is able to penetrate... waterproofing ontop of foam though? you have no monolithic structure, its like trying to waterproof over an ocean of foam packing penuts... there is no real foundation to prevent movement, and even the best waterproofing ( hot mop asphalt + motified butyl rubber) has an elongation rating of only like 1,100% of a max gap space of like 1/16th of an inch.

i guess what i'm really asking is would i be better off growing 100s, 150s or raised beds? i wanted to do raised beds but will the higher water table negatively effect growth?

if the place fills with water i dont see how it wouldn't effect your plants.

at the very least you could put down some decomposed granite to get your beds off the ground, then pump the water out. but any flooding not handled by the sump will result in the fertilizer charge being washed out.

i ran into this when i was growing in this enclosed atrium with a concrete floor and anemic floor drain... water would come up like 2 inches when the street started flooding. then you get like a week of spindily growth while your fertilizer charge is replaced via regular irrigation via sprayers/drippers.

It'll be some work but why not raise the floor with some concrete footings n that trex decking so that things aren't under water when it floods ... how tall is it... no matter how you look at it that water will be an issue that needs to be addressed first..

trex decking is about the most expensive shit on the planet. you could build a deck from dinosaur fossils for less money.

stoney917 said:

It'll be some work but why not raise the floor with some concrete footings

Click to expand...

wait what? concrete footings? you mean like stem walls?

lol thats insanely over kill... you would be better off just relocating the greenhouse and reassembling it onto some engineered fill.

ive seen what you are talking about done for HOUSES... usually houses built on failing stacked stone walls, or houses that are being renovated and the existing stacked stone is no longer sufficient... but a house is worth 10x what a greenhouse is worth so it makes far more sense.

its alot of work dude... alot more work than i think you recognize.

to retrofit a foundation into a structure requires underminning and the placing of false work to support the structure while you erect your concrete formwork.

alot of times to save fancy historic houses they will just run steel girders under the foundation... cut the house up into manageable sections, reinforce everything, replace anything that is suspect, and just move it off the existing foundation and set it down like 100 feet away ontop of hardwood blocks bearing onto compacted earth or driven piles or what ever the soil requires. but again the cost is ball smashing.