Allotment greenhouse build options & considerations

[Forage420]

I would use untreated sleepers. They're massive great big things... how long are you planning on having the allotment for? I'm pretty sure they'll see you out!

As for how they'd sit, you've got them lying flat in you pic, i would have them on their edge so you get more height from each one. At the upper end of the slope the lower one would be completely in the ground and the top of the second one (on top of the first) would be flush with ground level. As the slope comes down to the front, the lower one would gradually be visible above the ground level and the second one on top would be well clear of ground level at that end giving you more growing height at the lower end of the slope and less height at the upper end... or just drag some soil from inside the greenhouse at the upper end as you'd now have a retaining wall (of sorts) to be able to level the soil out inside the greenhouse.

In terms of wetting/drying, i don't think i will be a massive issue due to the size of the things.

I plan to keep the allotment indefinitely. The websites I have found that supply sleepers in London are actually quite expensive, added to this is the cost of delivery. Can you find anywhere that would supply 4 sleepers of reasonable size and robustness for under £100 all in ? I'm struggling. Your idea is a very good one however, don't get me wrong, and I value your opinion on it, if I was to ever go for another greenhouse where I haven't already dug the trench, and where the ground is reasonably flat, I would definitely consider it as a first option. The look is good too, perhaps if I had a garden untreated sleepers would be nice.

[Forage420]

I should post a link to my foundation build but its on a different site so I wont. I did mine with class b engineering bricks, the ground sloped 1 in 8 over the width.

If this in on the plot and not your garden I think you've overthinking it. If you're allowed blocks onsite, get some lightweight aerated concrete ones (£1 each even at B&Q) put these in your trench dry (no mix at all) on edge to about 6 inches, level them off. Get yourself some treated 1x4 put this on top of the blocks and screw through the wood into each block. Solid footing done, no mortar, wet concrete or anything else. if you need to remove it or move it everything should come apart easily.

If you want it higher screw some 4x4 fence posts to the 1x4 frame, if you want to add some extra protection for the 1x4 put some DPM between the blocks and the wood but I wouldn't bother.

I've decided on a way forward and will update with photos so that I can share them here. More to come ..

[nickdub]

I've decided on a way forward and will update with photos so that I can share them here. More to come ..

Thanks for letting us know - and good luck with your project.

[Stan79]

I plan to keep the allotment indefinitely. The websites I have found that supply sleepers in London are actually quite expensive, added to this is the cost of delivery. Can you find anywhere that would supply 4 sleepers of reasonable size and robustness for under £100 all in ? I'm struggling. Your idea is a very good one however, don't get me wrong, and I value your opinion on it, if I was to ever go for another greenhouse where I haven't already dug the trench, and where the ground is reasonably flat, I would definitely consider it as a first option. The look is good too, perhaps if I had a garden untreated sleepers would be nice.

Last lot of sleepers i got were off ebay... Not sure where you are in London but yes, i can find 4 for under £100. Delivery not included though.