How to fill 1" gap between door frame and lintel

[Greggerly]

hi guys
I will be cutting opening in the garage and fitting personnel doors. It seems I will end up with a 1" gap between the door frame and lintel. Whats the best way to fill it? Simply fill it with mortar or is there a smarter way? I know there are infill panels available but it seems overkill as they're mostly for much larger gaps.
thanks

 

[big-all]

is it wood or plastic frame/door??
would raising the door a bit reduce the gap in a practical way ??
doors between garage and dwelling need a 100mm threshold as a barrier against flammable liquids and fire

 

[Greggerly]

It’s metal. Doors are between garage and garden so no need for additional threshold although it’s already about 100mm above ground from the garden side. I could fill the gap with wood planks as I have plenty but door frame is only bolted on the sides so the gap above needs filling only for visual purposes

 

[foxhole]

You could screw your timber to the frame before install, or just foam it.

 

[thomp1983]

1 inch steel u channel welded on top of door frame, painted same colour as door it should look as if it's part of the original door