Allotment Greenhouse - Best base without cement use?

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Hi all! First post here.

I'm about to take on a plot in my very first allotment and I'm absolutely too excited. Cannot wait. In the meantime we managed to procure a greenhouse on facebook which is in pretty good nick absolutely FREE. It's approximately 6ft x 6ft (picture attached). Feel very lucky. Have been to visit in the evening but didn't really have much time to start dismantling so we are planning on doing that on Wednesday. No broken panes, frame didn't look at all warped, no gaps etc. Feels like I've struck gold!

Anyway onto the question. My allotment (down in gosport), like most, doesn't allow for the use of any concrete, cement, permanent structures etc. Looking across the site you can see a few greenhouse frames without any glass looking extremely sorry for themselves, so I'm guessing it can get pretty windy there. From just glancing around, most of the ones I could see had just been laid on top of the soil.

My current plan is to dig out an area for the perimeter of the frame, maybe an inch or so deep, tamp down the soil good and proper, and lay down some paving slabs. Paving slabs will just have to sit on the soil. On top of that will sit some kind of timber (treated fence posts? used railway sleepers?) and I will fix the bottom of the greenhouse into the timber with screws.

How does that sound in terms of stability and longevity? Is it hopeless? What would be the best timber to use? Should I treat it myself (and what with?) Are the paving slabs a waste of time?

I am a relative beginner when it comes to greenhouses so absolutely any and all advice is welcomed.

Thanks so much!



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Re: Allotment Greenhouse - Best base without cement use?
« Reply #1 on: October 22, 2019, 13:19 »
Many different ways of doing this of course, but to gain useful extra height with the least expense, and also avoid the need to source wood and worrying about protecting it, I'd suggest using concrete breeze blocks part-buried lengthwise in the soil (not the lightweight aerated ones of course.)

The greenhouse base can then be screwed to the blocks using heavy duty screws and plugs (you will need a masonry drill.)

Preparation is everything - the trench you lay the blocks in must be well tamped down as you are already aware, and must be absolutely square and level, although I'm sure you'd get away with using a little bit of mortar on top to level them up if necessary when offering up the frame.

Apart from being relatively cheap, it gives you the option of either paving the inside, creating a path down the middle with soil borders either side (or half and half if you wished.)

In the absence of assembly instructions, it's a good idea to take a few pics of the GH before you start dismantling it. ;)

Good luck!
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Re: Allotment Greenhouse - Best base without cement use?
« Reply #2 on: October 22, 2019, 14:32 »
I am perhaps in a slightly different situation, this is my own garden, not an allotment and 40 years gardening on this plot so far so able to make a judgement about wind etc. My two greenhouses 8 by 6 and 16 by 10 were screwed to a  1 block high concrete block dwarf wall laid on paving slabs on soil. They were like that for about 30 years, no probs. Had to dismantle and move both last year as we build a bungalow in the orchard and needed to put in a new drive. I am about to rebuild both and because I am 30 years older I am less inclined to want to mix mortar and build walls now I am going to level the soil, ram down a bit and lay sleepers to perimeter and to form inner bed edgings with narrow gravel path up middle and under staging areas. In other words I am sort of building raised beds with greenhouse screwed down on top. Does that make sense ???. I am buying new 200 by 100mm sleepers so I know what preservative they have in them. I might make sleeper wall 2 rows high (400mm) as I am tall and like good headroom over potting bench etc, that would also make sleeper wall very heavy against wind. Hope that gives at least one view.


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Re: Allotment Greenhouse - Best base without cement use?
« Reply #3 on: October 27, 2019, 15:57 »
I've installed 3 over the years with both metal and wood (treated fence posts) bases. To fasten down I've used metal tie straps (got mine from Wickes) cut to a suitable length and bent into an 'L' shape. Bolted to the base with the L buried they make pretty firm anchors.



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Re: Allotment Greenhouse - Best base without cement use?
« Reply #4 on: January 24, 2020, 15:31 »
For the shed I would go with 3 x 3 inch fence posts.

To comply with the rules get some house bricks, the sort with holes all the way through. Lay these on builders sand (easier to tamp down than soil)  Use two side by side per position, 4 would be better making double height. Each position should be about 2ft apart then lay fence posts on top in the opposite direction to the runners under the shed floor.

There are two advantages to this method, firstly the wood does not touch the ground and secondly being above ground it may assist in keeping the rats out.



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Re: Allotment Greenhouse - Best base without cement use?
« Reply #5 on: January 24, 2020, 16:52 »
when we built our first greenhouse we used railway sleepers they where buried in the ground and fixed the greenhouse to the sleepers with coach bolts  it never moved until we took it down when we moved house and even then the sleepers were as good as when we buried them several years ago 

we have two large greenhouses built on a concrete base now but that's on our own ground but I now you have to comply to allotment regs depending on your landlord good luck with the installation

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