Closing gable cavity with foam?

[SGAsp]

Hi all BC said 'top up cavities and fit closers'
My issues is the gable wall.
The bricks/blocks are rough arsed so cant use the plastic tray with foam attached.
Could use the sock style but cant get them today.
Was wondering about expanding fire - specifically fire rated.

No Nonsense Fire Rated Expanding Foam Hand-Held 750ml

Order online at Screwfix.com. Fire rated hand-held PU foam with high thermal and acoustic insulation properties and up to 240 minutes fire rating. Excellent adhesion on most substrates. No shrinkage. Paintable. FREE next day delivery available, free collection in 5 minutes.

www.screwfix.com

Fire rated and seals against smoke and gas which to me means air tight?

Anyone had experience with it?

TIA

 

[23vc]

Insulation normally just stops level with top of masonry and battens and membrane cover it, unless somethings changed? You’d only fit cavity closers around windows/doors/internal breaks in the cavity