I need to do some lean mix cavity fill about 3-4 courses high, mixing with a cement mixer.

What is the recipe?

 

We used to do 12:1 ballast to cement semi dry , almost anything will do 

I used insulation to stop a thermal bridge from the cavity infill of concrete, building inspector accepted it. We lowered the DPC in line with the inner floor level and added an extra DPC in the outer brickwork to cope with rain bounce (DPC 6” above outer ground level).

Edited August 31, 20215 yr by joe90

+1 to the insulation and just make it 10-20mm less than the cavity and weak mortar mix of 8:1 to hold it in place. Needs a second DPC as per @joe90

21 hours ago, tonyshouse said:

We used to do 12:1 ballast to cement semi dry , almost anything will do 

 

I have loads of 20mm clean stone and sand on site.

Rather than order in ballast what ratio of that should I mix in?

7 ballast

 

5 sand

 

1 cement