Rip up sub-base or screed over it?

[donnerblock]

Is it possible to use screed/pointing material as the SURFACE of a patio?

I removed the broken crazy paving from our 6 m x 2 m patio in preparation to lay 400mm x 400mm slabs. I thought that all of the sub-surface was friable (the first bit I uncovered broke up easily). But it has turned out to be solid as a rock, and 150mm thick over 90% of the area.

Aside from the fact that it is going to be a real job to rip this sub-base up, the area includes two rectangular drain covers (one of which is at a 45 degree angle to the house, and seems to be fused to the sub-base) that are going to be difficult to incorporate into the slab layout. So, screeding the existing base with the same material would solve a lot of problems.

The patio will only have a table and chair set, and a few pot plants on it.

Thanks in advance for any advice.

 

[r896neo]

You can use screed i.e 4:1 (grit sand:cement) but its not really hard enough and will gradually scratch and gouge. Concrete would be more suitable but would need to be a minimum of 75mm thick.

 

[donnerblock]

r896neo,

Thanks for the reply.

Looks like I'll have to hire a demolition hammer to break up the old sub- base.

Do you know how deep the drain covers are likely to go? I'm worried about using a breaker around them.

 

[r896neo]

depends on the type of cover, lift them first to check for shallow pipes