Regardless of the age or condition of any existing intumescent paint protection applied to structural steelwork, it is possible to apply a boarded encasement system around the steelwork without any detrimental effects on the performance of the boarded system. 

The steelwork section factor will still need to be evaluated in the same manner as would be required for a standard boarded encasement arrangement, which will be inherently lower than that for a profiled protection system, and the fire performance of the existing intumescent paint cannot be taken into account when adopting this approach. 

The intumescent action of the paint will not impair or reduce the performance of the boarded encasement system applied over the paint. This advice is based on the Technical Guidance Document 8, issued by the Association for Specialist Fire Protection (ASFP): “Code of practice for junctions between different passive fire protection systems when applied to load bearing structural steel elements".

In terms of the advice given for junctions between existing intumescent paint and a boarded system the document states: “Where a board meets a reactive coating, the board system should overlap the reactive coating by 100mm, and then be capped off, noting the need for chemical compatibility of any materials/adhesives with the reactive coating system.”