Hardcore compacting , do stones need compacting too?

[Ady J]

Hi all

preparing land ready for foundation dig,
I have tons of stones that I removed from garden prior to digging out soil for lowering/levelling

I’m thinking of using some of these stones in the trenches prior to concrete pour

I’ve read that stones do not need compacting is this true?

Thinking about broken hardcore the cheap usual stuff that’s used is lite weight in comparison & would need pressing down , stones due to mainly a regular shape & very dense perhaps not needing compaction

Anyone ok the know?

 

[Ian H]

Is it normal to put anything other than concrete in the trench?

 

[Ady J]

Is it normal to put anything other than concrete in the trench?

Just looking at options
Doing a raft foundation so considering a layer of stones for concrete to pour upon

 

[^woody^]

Is it normal to put anything other than concrete in the trench?

People occasionally. Apparently.

 

[^woody^]

Just looking at options
Doing a raft foundation so considering a layer of stones for concrete to pour upon

Yes that will be a brilliant test of a raft. But the raft might become a submarine. And if you're the captain, you know what you'll need to do.

 

[Ady J]

I take it no one knows lol, same boat as me then

 

[Ian H]

I wouldn't do it. I'd go 100% concrete.

 

[Notch7]

I presume this a not under building regs?

If it was, you would need a structural engineers design for the raft.

As I understand it, a trench foundation should have a flat bottom to trench, I know building inspectors like the 'crumb' removed.

On that basis, I cant see using hardcore as the base of a raft skirt being correct. A builder would never do it because it just means digging out more, only to put some back.

 

[noseall]

On that basis, I cant see using hardcore as the base of a raft skirt being correct. A builder would never do it because it just means digging out more, only to put some back.

Perhaps the OP has mistaken infilling the slab part of the raft with hard core material rather than the trench?

 

[Ady J]

yes sorry, its the centre ( 150mm thick ) part , the outer border trench is 700mm deep by 600mm wide no need for stone in these sections

no structural engineer on this one, although I've used them in the past & on same land so I have a decent idea,
If I didn't know the land and/or the build was something bigger then I'd get one into be safe -but I pretty much know what their patter would be (my pal is one and for most standard domestic single storey its usually very basic but they have to make it all sound strict and complex etc )

I am also 4 meters away from closest drain system, 2 meters away from house so nice and safe

its a standard single storey outbuilding so this type slab foundation is a bit of an overkill but I prefer it this way