Filling window gap.

[craig1]

Hi, I'm looking to fill a gap between a wooden sash window and the wall. Should I just use mortar or is there something easier to put in which will stay in. The biggest gap is 20mm.

Thanks
Craig.

 

[tony1851]

Expanding foam - but mask off adjoining areas first

 

[craig1]

Thanks for the reply Tony,
Expanding foam inside the joint and mortar finish or just use the foam so it sits just below the surface? Think the mortar will come loose again overtime.

 

[noseall]

Ex-foam and cover beads.