dpc level cavity fill

[helpneedhelp]

Hi can someone please tell me how im supposed to fill my cavity up to dpc level, I have been told that it should be a lean mix of contrete sloping towards the outside leaves. Is this correct and what is considered a lean mix?

Thanks

 

[noseall]

don't under any circumstances fill the cavity all the way up to dpc. the concrete must finish 225mm below dpc.

chuck it in, level and tamp it with a stick.

mix it 8:1

 

[helpneedhelp]

8:1, Being 8 Parts Agregate (chippings to dust) to 1 part cement

 

[noseall]

8:1, Being 8 Parts Agregate (chippings to dust) to 1 part cement

no. 8:1 being 8 parts ballast (sand 'n' gravel mixed) to one cement.

 

[helpneedhelp]

thanks noseall can i ask why does this need to be done?
On the building regs it shows a picture of the mix being sloped towards the outside wall of the cavity.

 

[noseall]

this so that the walls don't collapse into the cavity when you start compacting stone and soil around them.

most important me thinks.

the slope on the concrete is there to deflect any water out and away from the internal wall should any find its way into the cavity.

 

[helpneedhelp]

ok my cavity is only one block high to dpc, so that would only give me about an inch of concrete to allow my 225mm clearance is that enough?

 

[noseall]

don't bother even filling that amount.

only one block high! i hope you're not thinking of fitting any drain gulleys close to the wall are you?

 

[helpneedhelp]

I have gone one block high, because ive done a trench fill foundation
and i have hade to step up my dpc about 50mm