p.millatt Posts: 2
We had two greenhouses in the back garden , since next door to their Silver Birch down our greenhouses have had lots of water in. My husband has had both greenhouses removed and he wants to buy a new one , but ground is so soft and spongy he is concerned about laying concrete for the new greenhouse.
Any suggestions please . we considered a sump just dont know if it will fix it . Back garden is clay soil .
When you say 'lots of water in' - you mean they were leaking or that water was coming up through the ground? Are you in the dry south or the wet north?
we are in the N W , ( wet North ) the greenhouses were filling up with water and it was not draining , now they have been removed and the ground has been dug over there is a large area thats very spongy , soil does not look clay its dark soil but all around here is clay ,the water inside the greenhouse was from leaking , the area around the greenhouse was not too bad , it drained from the outside areas .. Hope this makes sense ,, just this area of soil from where the old greenhouse had stood
Hmm. I think you may need to try to work out why that patch of soil is markedly different to what's around it in case there's a broken drain or old Anderson shelter or goodness knows what else under there. Has there been a garden there for a long time or is it a fairly new (post war) housing development?
If you put down a solid concrete slab straight onto the ground, water will probably come through it. A patch of less clay soil in a large area of clay acts as a sump (which is why if you garden on clay you'll be advised not to dig large holes for new plants - they end up sitting in water). It's possible that this is what's happening, so you don't need to make a sump, you already have one. You could put in a land drain of some sort to take the water out of that 'sump' but that depends if you have somewhere to drain it to. It would be illegal to connect that to a public sewer (in case that crossed your mind).
If the tree that's been taken down was very large, it's removal could cause quite a lot of ground movement as the roots die and decompose. If you were building a house there, you'd be having to dig really deep foundations, but a greenhouse is less of a problem - much less weight and much less risk should subsidence affect it.
On balance, I would be inclined to put the new greenhouse somewhere else and let that area 'settle' for a couple of years - see if you end up with a swampy pond or if it stays dry. Otherwise you may need to take a rather more complicated and structural approach than would be normally needed for a greenhouse.