Opinion needed

taxignorant

Hi folks, just finished extending a new house. When digging foundation builders found "backfill" and we had to put in extra concrete up to nearly 2m.

Despite me pleading with them not to spread rubble in garden, that is what they did. Even went as far as spilling out leftovers from the outside render and bags of cement. I think these have now set in the rain.

The garden slopes away from house and is around 6 inches lower than the path around the house.

My question is do I need to dig this all out and remove it in skips? Or can I lay down soil and topsoil over winter that will start breaking up the ground? I would be able to build garden up around 6-10 inches with topsoil without upsetting the gradient/drainage.

I would like to plant some trees, create a patio and have some lawn and beds for veg/flowers. Will trees and shrubs be able to root down enough if transplanted in from nursery - I had wanted to get some large ones in order to block out a derilict building next door with broken windows / barbed wire on it.

I'll try attaching pics.

macraignil

It would be difficult to say what is best to do in that situation without being able to dig about the area and checking details of how much rubble you are talking about and the available area of the garden etc. You mention you would like to create a patio, plant some trees, shrubs and have a vegetable and flower area. These different uses of the ground would have different requirements in terms of soil quality.

It would be fine to have rubble under the patio and even some trees, shrubs, herbs and flowers will do better on poor quality soil. Lavender, lupins, alpines and wild flower mixes will often do better on poor soils as that is the type of ground they are adapted to grow on. Too much nutrients will not help these plants and help weeds become more of a problem. Trees and shrubs will send roots deep into the soil once established so the quality of the surface soil is not as much of an issue. Growing vegetables on the other hand should benefit from good quality soil and harvesting and cultivating the ground would be much easier if rubble is not a problem.

As you mention not changing the gradient of the garden is important and water should still be able to flow away from the house. Keeping this in mind I would consider moving the rubble to the area you want to turn into a patio, perhaps digging out any good soil in that area first to use elsewhere and make more space for the rubble. Depending on how much rubble is left then, you could establish an area for plants that do not need very fertile soil. If there are solid lumps of render that has set over a wide area you may need to break these up to allow water drain through. If drainage is a problem then only particular plants will survive as most will be killed when their roots drown.

To get back to your original questions: I can not tell if you need to dig all the rubble out and remove in skips without an idea of how much rubble there actually is, what the gradient of the site is and what area you have to dispose of the rubble on site under the patio etc.
Soil will not in itself break up the ground but strong growing roots and earth worms will.
What trees and shrubs will do well in poor soil depends on the varieties you choose.