# Forum Home Renovation Concreting  Can I concrete over tree stumps?

## anawanahuanana

Hi all. Quick question if I may. I'm looking to put down a shed slab (4 x 2.5) and the area where it has to go has 4 large palms of some description (approx 4-6m high each, and a load of golden canes. If I was to cut these down at ground level, what would happen in the future if I was to lay the slab on top? Would the stumps eventually turn to mush and cause the concrete to sink or crack? I really don't want to go down the road of digging up stumps obviously, but what are my options? 
Thanks in advance.

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## kombiman

> Would the stumps eventually turn to mush and cause the concrete to sink or crack?

  yes, exactly the reason to remove them and put a solid foundation for the slab.

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## PlasterPro

asking for trouble down the track 
when you go to back car in shed :No:

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## anawanahuanana

Thanks guys. As I suspected. The only reason I was contemplating it was because it's going to be a fairly light duty shed, as in just holding a small workbench, some toolboxes and a lot of boxes of "stuff" from in the house. I figured with only a relatively light load on a reinforced 100mm slab, the area (less than 1sqm) we are talking about may not amount to much.
However, I guess I'll have to either pull another load of cash out of my ar*e to pay for a stump grinder and then hire a compacter to put a load of road base down over the top, or get busy with a pick axe and my lovely clay soil......... :Cry:  :No:

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## johncs

> Thanks guys. As I suspected. The only reason I was contemplating it was because it's going to be a fairly light duty shed, as in just holding a small workbench, some toolboxes and a lot of boxes of "stuff" from in the house. I figured with only a relatively light load on a reinforced 100mm slab, the area (less than 1sqm) we are talking about may not amount to much.
> However, I guess I'll have to either pull another load of cash out of my ar*e to pay for a stump grinder and then hire a compacter to put a load of road base down over the top, or get busy with a pick axe and my lovely clay soil.........

  We have a cracked, uneven concrete patio. We're contemplating low (a few cm) decking to cover over it. 
In your case, a wooden floor should be fine, whether on stumps or supported by concrete, and nicer to walk (and drop things) on.

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## Planned LScape

This happened at a mate's place I saw, where a slab was laid as a foundation for a BBQ. There was a pittosporum stump underneath, and I presume as the wood rooted down the slab moved down too. Now there is about a 25mm drop from the surrounding paving.

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## Bloss

Best practice would be to remove, but IMO this could be managed by properly reinforcing the slab - and since you are able to identify where a future weakness might occur add an addition layer of reinforcing at those points - with sufficient overlap of course. 
If cost is a factor then additional reinforcing the whole slab for a 4m x 2.5 shed might be cheaper than paying to grind out. Even making the slab 120mm thick and doing a double sheet of re over the lot would be sufficient over-engineering even if someone later drove car into it. The additional incremental cost isn't all that much and is easy to do. 
So - do the sums on the two options including labor costs (which will be negligible for increasing the slab depth and adding one extra layer of reo) and see what it looks like. Then decide.  :2thumbsup:

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