Forum home› Problem solving
This Forum will close on Wednesday 27 March, 2024. Please refer to the announcement on the Discussions page for further detail.

Greenhouse Base advise, please?

FuturllamaFuturllama Posts: 5
in Problem solving
Hi fellow gardeners! 

We have just removed an old rotten shed that was stood on this concrete base and we would like to add a green house in its place.

I worry that all this water will cause problems in the greenhouse. Does anyone know the best way avoid the green house being flooded every winter?

Attached a few pictures to show how it looks after a few days of rain. Thankful for any advise. 

Thanks in advance  :)
«1

Posts

  • McRazzMcRazz Posts: 440
    edited 11 March
    The best way to avoid flooding would be to have a strip foundation for the greenhouse that sits below the walls only. Perhaps you can do this with what's there and cut away the excess slab if its substantial enough (Just don't get the brickie who did your retaining wall to do it :D ...)

    You can install a greenhouse on a slab but you'd end up with something more like a conservatory and as you say drainage would be a big issue. I know others on here have greenhouses like this but you'd be restricted to potted plants which is a complete b***ache in a greenhouse.

    That slab looks really low too - did your shed rot? 
  • FairygirlFairygirl Posts: 55,117
    It does look very low. I had to do a similar thing when I moved the shed that was here - put in concrete and slabs for the base. The water still gets in to the bottom areas, and I need to replace the shed this year. I'll be making the base a bit higher when I do, just to avoid any future problems. 
    That wall at the back with all the soil in it will make it harder to remain dry too. It's certainly a bit dodgy looking! 

    I agree that it's also more limiting for your growing when it's all in containers, but if it's the only place you have for it, there isn't much you can do. It depends what you want to grow too. Many plants are perfectly happy in containers, but you could build some raised beds which would be easier, assuming you'll have enough height for everything. 
    I wonder if it was originally a parking area or something?
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • FuturllamaFuturllama Posts: 5
    McRazz said:
    The best way to avoid flooding would be to have a strip foundation for the greenhouse that sits below the walls only. Perhaps you can do this with what's there and cut away the excess slab if its substantial enough (Just don't get the brickie who did your retaining wall to do it :D ...)

    You can install a greenhouse on a slab but you'd end up with something more like a conservatory and as you say drainage would be a big issue. I know others on here have greenhouses like this but you'd be restricted to potted plants which is a complete b***ache in a greenhouse.

    That slab looks really low too - did your shed rot? 
    Thank you so much for your input McRazz! I will look in to the strip foundation option for sure. 

    Haha! If I could find out who did it for the previous owner, I'd want to have words for sure 🤣 

    I think I might have to live with the potted greenhouse, maybe even grow bags if they are on a raised structure? 

    Yes, the slab is really low and yes, the floor of that shed was all rotten unfortunately! 
  • FuturllamaFuturllama Posts: 5
    Fairygirl said:
    It does look very low. I had to do a similar thing when I moved the shed that was here - put in concrete and slabs for the base. The water still gets in to the bottom areas, and I need to replace the shed this year. I'll be making the base a bit higher when I do, just to avoid any future problems. 
    That wall at the back with all the soil in it will make it harder to remain dry too. It's certainly a bit dodgy looking! 

    I agree that it's also more limiting for your growing when it's all in containers, but if it's the only place you have for it, there isn't much you can do. It depends what you want to grow too. Many plants are perfectly happy in containers, but you could build some raised beds which would be easier, assuming you'll have enough height for everything. 
    I wonder if it was originally a parking area or something?
    Hi Fairygirl and thank you for your reply! I really appreciate it.😊

    Interesting, how are you planning on making the base higher? Adding more concrete on top of the already existing slabs? 

    Oh, I know! If you think the brick work looks dodgy you should have seen the DIY electrics in the garden... One wire was cut, exposed and just buried in a few ft of soil. 

    If I want a greenhouse (which I really do!) I will have to just live with it, like you said since this is the only spot for it. I'm planning on growing the usual suspects like tomatoes, cucumbers, peppers etc. And to start some seeds in there that could later go outside. 

    Yes, height is a thing too! It was suggested to me to have the greenhouse be stood on sleepers as to raise it a few inches. Judging by the state of the wooden shed that was previously there I don't think that would be such a good idea for longevity. 

    Perhaps an option could be to add a layer of concrete to the existing slab, then raise the greenhouse frame up with something water resistant... 

    I think the slab was just laid as a foundation for the shed that was there, the garden is in three "steps" and this is on the middle step. The top step is that dodgy looking wall... 😁 
  • Joyce GoldenlilyJoyce Goldenlily Posts: 2,933
    I think once you have a watertight greenhouse over the base your problem will be minimal. A great many people have greenhouses on solid bases and only grow in containers so that is no problem. It saves digging out the borders to replace spent soil. My greenhouse is on compacted soil covered with weed membrane with a surround of breize blocks attached to the greenhouse, it works perfectly well. If you can dig a trench around the outside of the concrete and back fill with chippings/gravel to act as a drain it might help.
  • FairygirlFairygirl Posts: 55,117
    I think that's why @McRazz was suggesting another tier of concrete, or similar, just to raise the height of the base @Futurllama . It would all need to be securely done of course, and the greenhouse would then be bolted/fixed in place to that base. Not something I've ever had to do before though. Any greenhouse I've had in the past was pretty secure and 'river free' ! You can always add some guttering and have a water butt too if you get lots of dry weather in summer, as it saves using tap water. Always a useful resource. 
    I'll take a view on mine [shed] when I pull it down. It may just need a bit more ground clearance around one side in particular, which I can sort with paving slabs, or the aforementioned concrete blocks or similar, plus removing any soil that's got in.  For that base, I just recycled the huge slabs that were here , [plus a bit of extra concrete in the appropriate spots] and were forming most of the small, enclosed bit of the very  uninspiring 'garden' , but a blank canvas is something I always enjoy altering.  The joys though..... ;)
    I always grew my toms in pots, which is absolutely fine. I don't grow them, but cucumbers and peppers are usually done that way too- many forum members grow them.
    I use mine over winter for small plants or cuttings if needed, so some shelving will probably be useful for you, as well as being handy for storing pots, watering cans etc. Mine is small, so I keep most of that stuff elsewhere.  :)
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • Busy-LizzieBusy-Lizzie Posts: 24,043
    edited 12 March
    I think @Joyce Goldenlily has a good idea - to dig a gravel filled trench to act as a drain. It is called a French drain. We had one done at my old French house. The house was on a slope so the sitting room floor was about 2 feet below the land outside the house wall. The house was old and built of stone. There was heavy rain the first year we were there and the water seeped through the wall so we had a French drain dug. We never had the water on the floor again.
    I found this site which explains.
    https://www.homebuilding.co.uk/advice/what-is-a-french-drain
    Dordogne and Norfolk. Clay in Dordogne, sandy in Norfolk.
  • McRazzMcRazz Posts: 440
    It doesnt look like you can dig any drainage in anywhere. 

    If the slab needs to remain then you could mark out the greenhouse footprint and then trim away all excess concrete to prevent water ingress from outside. 



  • FairygirlFairygirl Posts: 55,117
    That's what I was wondering @McRazz. Where/how could you dig out room for drains without using a digger, and probably removing/renovating that wall as well? 
    The other alternative would be to fill the entire space with concrete so that it's the height of, or higher than, that step up on the right, but the fence etc on the left might then be a problem, plus the back wall area, as well as it being pricey. 
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • FuturllamaFuturllama Posts: 5
    Joyce Goldenlily said:
    I think once you have a watertight greenhouse over the base your problem will be minimal. A great many people have greenhouses on solid bases and only grow in containers so that is no problem. It saves digging out the borders to replace spent soil. My greenhouse is on compacted soil covered with weed membrane with a surround of breize blocks attached to the greenhouse, it works perfectly well. If you can dig a trench around the outside of the concrete and back fill with chippings/gravel to act as a drain it might help.
    Thank you lots for your comment, Joyce! This does sound like a good option if the ground allows me to dig a mote all the way around the bas, then fill it with gravel that allows for drainage. 
Sign In or Register to comment.