In case of small gaps, it can be assumed that the insulation layer builder will bridge them in the event of a fire by foaming.
The surface in the gap should be coated as deep as possible.
For larger gaps, the void should be filled with mineral wool for example (melting point > 1,000 ° C). For aesthetic reasons, the filling material can be coated with the topcoat of the system used. The manufacturer of the intumescent coating should always provide product- and project-specific recommendations.