How to seal gap between door frame/LECA?

[inspectah44]

Have just installed a door in the garage's storage section. The garage is still uninsulated but will be insulated during the winter. On the slab, I have laid one course of leca. What would a reasonable solution look like for my problem? How should I protect the frame from moisture? Unfortunately, it doesn't seem to be possible to attach images right now.

The gap is about 15 mm wide and 120 mm high. On the other side, there's a smaller gap, about 5 mm. There was a little masonry blunder.

 

[Matti_75]

Plasticized caulking strip.

 

[KnockOnWood]

Foam sealant seals against potential moisture and secures the frame's position.

That would be my choice.

To "protect the frame from moisture" coming from the outside, surface treatment in the form of priming and painting is required.

 

[inspectah44]

Thanks for the tips. However, I think I expressed myself a little confusingly.

Since I won't have trim going lower than what the picture shows, I was actually wondering what one should use to seal it from the outside. Some type of caulk maybe? I will insert the backer rod from the inside afterwards.