How to fix OSB to Celcon type blocks?

[Mr Punter]

I am building up to a neighbouring house and the top section is built in no-longer-rendered Celcon blocks.  The render has part fallen off so I have removed the rest.  We have a valley type gutter going in between their house and our new project and the roofer wants us to fit 11mm OSB to the Celcon wall so he can fit the membrane which will line the gutter and be dressed up the wall and under a metal coping.

 

I quite like the idea of a combination of mechanical fixings plus adhesive but I don't know what would work best.  It is fairly high up and I don't fancy a return visit if the boards start to come away.

[Dave Jones]

stixall and plugs/screws every 300 staggered, staple a length of dpc to the back of the osb first for belt and braces.

[Mr Punter]

3 hours ago, Dave Jones said:

stixall and plugs/screws every 300 staggered, staple a length of dpc to the back of the osb first for belt and braces.

 

So this is an external wall.  Is it Stixall then OSB then dpc?

[PeterW]

Dryfix foam and something like Rawl multiplugs every 4-600mm will be fine.