Hmm, why are they putting a layer of hardcore and gravel, and then pea gravel, down there?
I would just remove all hardcore and crap down to about a foot deep, break up the existing soil to improve drainage, and bring up the level with new topsoil. Simple!
If the soil remains poorly draining there's more options to explore but simply adding hardcore and gravel isn't necessarily helpful.
Surely, broken up clay/sand is just going to mush back together again after a very short time. It's not actually soil down there. The hardcore and gravel will improve drainage, I mean, isn't it just a giant flower pot with grit at the bottom?
If you took a giant flower pot with grit at the bottom, sunk it into pure clay and ran a hose into it, would the grit help, or would the pot fill up with water anyway?
"What is hateful to you, do not do to your neighbour".
Clay soils are always less free draining than others, but what can make things worse is when they are compacted - squashed and compressed - so that they form a dense layer that is almost like a puddled pond. It is possible to break through this layer and improve drainage. You should always avoid digging it and walking on it in wet weather. If problems persist, adding organic matter to the soil in successive years can improve things quite a bit too.
"What is hateful to you, do not do to your neighbour".
If you took a giant flower pot with grit at the bottom, sunk it into pure clay and ran a hose into it, would the grit help, or would the pot fill up with water anyway?
The depth of the hole is important for it to work. A foot of soil on top of 6 inches of grit is better than just a foot of soil, or 1'6" of soil.
I agree totally with @Loxley. It's rotted manure you need in there - and any other organic matter you can get - leaf mould, compost etc. Layering hard landscaping with soil or any other organic matter doesn't work properly. You would mix grit or gravel with the organic material - you wouldn't layer it. Personally, it sounds like they're either taking the cheaper option, or they think plants will grow in the same conditions that paving likes.
Sand is every bit as problematic as clay in terms of getting a good growing medium. Adding more inorganic material to a lifeless medium just compounds the problem.
It's a place where beautiful isn't enough of a word....
I live in west central Scotland - not where that photo is...
Personally, it sounds like ... they think plants will grow in the same conditions that paving likes.
Accurate! They're rushing, but also respecting my wishes. I only, naively, bought two bags of soil enricher and two bags of componst to mix in with the inevitably "top quality" soil they arrive with today. Fairygirl said:
It's rotted manure you need in there - and any other organic matter you can get - leaf mould, compost etc. Layering hard landscaping with soil or any other organic matter doesn't work properly.
What should the soil to other matter ratio be? Noted to add over the years Also, thanks @Loxley & @Fairygirl!
It wouldn't really matter how much you add - there's no specific ratios really. The idea is to get a friable, loose mix to suit the planting. The quality of the topsoil and the effect of the building/walls etc are factors, because, as well as your climate, that dictates how much water gets into the bed. The planting will eventually take up moisture too. Just add organic matter and mix it all together, but break up the base properly first, as already mentioned. It will all gradually break down and improve the soil structure.
It's a place where beautiful isn't enough of a word....
I live in west central Scotland - not where that photo is...
Personally I would let them do the topsoiling and then deal with organic matter myself. If it was me I would lay about 75mm of composted bark to the surface of the topsoil and then lightly incorporate it. Adding organic matter in larger quantities is useful for heavy clay soil (to improve soil structure and drainage) but if your soil isn't heavy clay it's more a case of tailoring it to what plants you want to grow. Some plants appreciate a richer soil than others. You may also find that the imported topsoil is already quite rich in organic matter. The stuff sold in bags usually will be.
"What is hateful to you, do not do to your neighbour".
It sounds as if what's in the bottom of the hole is the subsoil. If the house is on the new side the topsoil was probably stripped off before it was built, and only put back where there wasn't paving.
If the bottom of the hole (however deep it is) doesn't drain at all, no amount of layers of gravel etc will stop it filling up when there's a lot of rain. If it drains, but slowly, the gravel etc might help if it's deep enough to be below the plants' root zone. I would still try to break up the stuff in the bottom, mix in gravel or whatever, and test the drainage before spending time and money filling it up with topsoil and organic matter.
Doncaster, South Yorkshire. Soil type: sandy, well-drained
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It's rotted manure you need in there - and any other organic matter you can get - leaf mould, compost etc. Layering hard landscaping with soil or any other organic matter doesn't work properly. You would mix grit or gravel with the organic material - you wouldn't layer it.
Personally, it sounds like they're either taking the cheaper option, or they think plants will grow in the same conditions that paving likes.
Sand is every bit as problematic as clay in terms of getting a good growing medium. Adding more inorganic material to a lifeless medium just compounds the problem.
I live in west central Scotland - not where that photo is...
Also, thanks @Loxley & @Fairygirl!
Just add organic matter and mix it all together, but break up the base properly first, as already mentioned. It will all gradually break down and improve the soil structure.
I live in west central Scotland - not where that photo is...