Chalk In A Sub Base

[Onoff]

For my patio sub base I'm using a lot of the local flint that I'll whack down. Up until now I've been picking out the chalk but do I need to? Seems hard enough a material, should whack down well and remain in place and sticky when damp. Thinking a whacked flint / chalk sub base then  sand/cement dry mix pre the slabs.

[joe90]

Sounds good to me 👍

[Gone West]

I would have thought the flints would whack down better with chalk in the mix as it will fill in the gaps like having fines with type1.

[Onoff]

On another forum, in part answer to the same question, somebody wrote:

 

"A good quality geo membrane under the sub base is the most important factor".

 

Really? Without diving into the paving expert site, is that really correct? 

[Mr Punter]

No point in the membrane.  It works OK as a separation layer, like if you are on clay.  Flint and chalk will be good as long as the chalk is not too putty-like.

[Onoff]

31 minutes ago, Mr Punter said:

No point in the membrane.  It works OK as a separation layer, like if you are on clay.  Flint and chalk will be good as long as the chalk is not too putty-like.

 

I am on clay. Thin top soil, clay, chalk. Flints in every layer

[Mr Punter]

On clay I would use Terram ono.  Stops the aggregate getting mixed up with the clay.