Best way to fill this gap around patio door

[Rantallion]

What is the best way to fill this gap around my patio door?

Doing some fixing up of plaster work around the house and pulled some cracked plaster away around my sliding patio door to reveal a very narrow cavity between the external brickwork and internal block work. The cavity has a narrow strip of DPC membrane running vertically down it but the cavity is only a finger's width.

House was built in 1980 and the door has been in about 7 years, replacing an existing sliding door. The surround was just patched up with plaster. All the advice I have found says to use a cavity closer but the cavity doesn't seem wide enough.

 

[jj4091]

Looks like the cavity has been returned, but not very well. The easiest and quickest and cleanest way to fix it would be to glue some upvc trim around the reveal.
Check you local shed.

 

[opps]

Mist the area with water and then squirt in expanding foam. Once cured, cut away the excess and then use filler.

The water aids adhesion and accelerates the curing time of the foam.