Mortar type / thickness beneath flags - Mortar type / thickness beneath flags

[KRT]

Hi,

I have an existing concrete base which I am planning on laying flags over (the concrete base actually forms the lid of a basement beneath).

I am constrained in terms of the finished levels over the concrete base either end. So on one side (the deepest section) after the thickness of the flag is taken into account i will be left with 170mm of void to fill between the bottom of the flag and the concrete. On the slimmest section it will go down to around 25mm bedding mortar.

Its my understanding that you shouldn't regulate with a mortar bed (i may be talking rubbish here). I did originally think of regulating with an asphalt concrete at the thicker end, but the laying temperature of this may cause havoc with waterproofing to the existing concrete lid.

Any thoughts / comments would be appreciated.

[Tony McC]

Apologies for being late to this - had all sorts of health issues with angina during the heatwave and now an arthritic knee that is driving me mad with pain.

Regulate with a C7.5/ST1 concrete until the depth of the regulating becomes less than 80mm, and then use a granolithic mortar.....or use all granolithic if it's not worth having two different mixes.

https://www.pavingexpert.com/mortars#mixing-on-site

https://www.pavingexpert.com/grano_01