Slab Base for a new greenhouse


I'm trying to get the ground ready for a new greenhouse (6 x 8). I've decided to go with all slabs as I see on earlier posts it's more practical for a small greenhouse.

I would like any advice on whether I can just lay them on a good rubble and sand base or do I need to cement them down? I'm hoping for the easiest option! 

Thank you

Cath image


  • I laid mine on very compacted soil and gravel, with some sand to help with levelling. You do need to get the dimensions right of course, but especially the levels, as otherwise the frame can be distorted and put pressure on the glass, potentially causing it to break.

    So far mine has survived 5 years and some very high winds and winter storms, but it is a lean-to, which probably gives some extra stability. It may also make a difference what kind of base comes with your greenhouse, as some are more substantial than others. I also used quite heavy slabs, 2'x2', the heaviest I could easily move by myself.

    Guess my answer is probably 'it depends...'image

    Last edited: 16 February 2018 17:19:17

  • For a permanent base and particularly for a 6' x 8 area, I would bed them down on a cement base. Basically, you have to consider the amount of foot traffic and then possibly they would lift and become more of a trip hazard. Another way you could approach it is laying a permanent perimeter of block paviours around the edge of the greenhouse so that you have a anchor point to fix the base. This then create a void space inside that you would fill with a 50mm depth of pea gravel, This has the advantage of been a lot cheaper in materials and labour and also allows  for good drainage 

  • Thank you both, I will check out the base it came with and the instructions...

    We are quite high up and in a windy spot so I guess I really need to do it properly. I like the idea of pea gravel inside, I understood from other posts that soil would be an issue in a small space (due to mould?) hence I was thinking of slabs. 

    I'm not the most practical person so I'm a bit apprehensive about cement and levelling but I think I'll just have to get on with it! 

    Thank you :-)

  • Hostafan1Hostafan1 Posts: 21,265

    "We are quite high up and in a windy spot so I guess I really need to do it properly."

    In the words of Roy Cropper:

    " if you fail to prepare: you should prepare to fail"

  • Yes you are absolutely right...but I fear I'm going to get it all wrong with the levelling hence I was hoping someone would say it would be absolutely fine not to cement it!! There's always Youtube I guess :-)

  • Hi Iancath 

    Block paviors are fairly easy to lay in a straight line. I would put your base together and ensure its at right angles. Lay in on the ground and mark out the perimeter of the base with an lawn edge. Cut way the marked soil to a depth 50mm and lay a sand and cement bedding wet mix at a ratio of 4 sand to 1 cement and lay your block paviors on that bed and use a level to ensure everything is plumb level lenght and width ways. After the blocks have set, reinforce them by laying a concrete haunching (laying concrete mix of 4 to 1 to both sides of the paviors to stop them moving. It seems a lot to do but if you take your time and get the paviors level. It can be done by an untrained hand. Then plug and screw your base on to the perimeter blocks. A fair trade person would not charge you much to lay around 9 metres of block paviors is a straight lines to fit your greenhouse on to 

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