Consolidated hardcore thickness

[Cavester]

Hi,

How do you determine the thickness of hardcore below a 125mm concrete slab?

My architect has specified 300mm yet most of the details I see note 150mm. I've looked at building regs and this just states between 100-600mm but don't see how the precise thickness is determined.

Thanks.

 

[John D v2.0]

The precise height is when you get from stable ground level that you started with to the right height for your finished floor level.
They mean you are not allowed to use more because it will settle. You also can't use less. 100mm seems a bit thin.

 

[^woody^]

Hardcore is only really necessary to form a consolidated base for the slab when the ground is poor, or to level up a base to receive the concrete slab.

100-150mm is enough. Any more and that would imply the ground is poor and should be removed anyway. Hardcore needs to be placed and consolidated in layers of 150mm, else it will compact over time.

I can't see any reason for more than 150mm to be specified unless the ground is known to be poor - in which case the resasons and requirement to remove the ground would be detailed in the specification too.

 

[Cavester]

Thanks Woody, this is as I expected. The ground is good and level. I'll worry it with the architect in case it's in error.