Bradstone natural slate

[Andrthms4]

started laying patio using bradstone natural slate using a bedding mix of 8-1(dust /cement),but found slabs laid on previous day coming loose or not bonding with the motar mix started using semi-dry then changed to a wetter mix to try and get more suction but no difference. may have to restart whole project.

any advice on how to get the mix to bond or stick better with underside of slab would be very much appreciated.

[Suggers]

What surface are you laying onto?

[Andrthms4]

laying it on whacked down sub base(scalping)
mix goes off great but doesnt bond or grip underside of slab(as if slab is too smooth)

[seanandruby]

try priming underside of slab with a unibond or, and a cementious slurry. use a semi-dry 8/10 to one for laying flags.

[Tony McC]

For a patio, I wouldn't get too worried about the flags not "bonding" to the laying course. As long as they're not rocking, the pointing should hold them in place and prevent any lateral movement. However, you may want to use a wetter mix for those flags laid to any free edges.

[lutonlagerlout]

if you havent pointed them ,then they will have a propensity to move laterally when walked on
like the gaffer says though ,rockers out
cheers LLL