Executed for principal contractor Collins Construction at 30 Finsbury Square, London, this nine month critical path passive fire protection (PFP) package delivered by Specialist Painting Group involved legacy coating ablation, surface preparation via abrasive blast cleaning, and multi-tier application of a certified cellulosic intumescent coating system. Operations were sequenced floor by floor within a live, logistically restricted urban envelope.
The brief at 30 Finsbury Square
The condition of the existing passive fire protection system at 30 Finsbury Square eliminated the option of direct intumescent coating application over the existing PFP system.
Operations enforced a strict tri-tier sequence per floor plate: legacy coating removal using RPR heat induction, dry abrasive blast cleaning to BS EN ISO 8501-1 SA2.5, and multi-component cellulosic intumescent coating application certified to the specified fire resistance rating.
Spatial and logistical constraints dictated a rolling zone methodology rather than a continuous monolithic workface. Shared vertical and horizontal ingress and egress, temporary scaffold integration, and weather envelope and roof sheeting interfaces required dynamic inter-trade co-ordination with a downstream finishing package.
Why passive fire protection starts with coating removal
Intumescent coatings only perform as tested when they are applied to a properly prepared substrate.
SPG used RPR heat induction to strip the existing coating. Heat induction removal breaks the bond of a coating system at the interface with the steel substrate using induced heat rather than mechanical impact tools or chemical stripper. It produces no blast media, reduces dust and noise, and captures the removed coating as a solid waste stream, which is essential on a confined city centre site with neighbouring occupiers.
Surface preparation by dry abrasive blast cleaning
Once the existing PFP system was removed, the steel was prepared by dry abrasive blast cleaning to establish the required surface cleanliness standard and surface profile. Approximately 360 tons of abrasive were used across the programme, an indication of the scale of steelwork treated.
Blast cleaning on an occupied site is as much a containment exercise as a preparation one. Voids and gaps were sealed ahead of each blasting phase to control media and dust, and blasting equipment was mobilised level by level as scaffold and roof works were completed above.
Applying the intumescent coating: PPG Steelguard 851 and 951
Two products from the same range were specified, split by exposure. The specified internal passive fire protection system was PPG Steelguard 851. The specified external system was PPG Steelguard 951. Both products were applied to achieve the required fire protection rating to the structural steel frame and cellular beams.
The Steelguard intumescent product range is used where a durable, spray applied passive fire protection coating system is needed for structural sections. Under fire conditions the coatings intumesce to form an insulating char that slows the rate at which the steel reaches its critical temperature, creating the time the building’s fire strategy requires.
Application followed a controlled sequence on each level: a stripe coat to edges, bolts and detailed areas first, then airless spray application of the intumescent material to the specified dry film thickness.
The outcome
Over nine months, SPG removed the existing coating system, prepared the steel and applied passive fire protection across the structural frame at 30 Finsbury Square, working alongside the wider construction programme throughout.
The project is a good illustration of what full scope passive fire protection application involves. The intumescent coating is the visible part, but structural steel fire protection only performs as certified when it rests on the removal and preparation work that comes before it, and on sequencing that fits the realities of a live construction site.
Specialist Painting Group delivers structural steel passive fire protection, corrosion protection and specialist coating applications across the infrastructure, petrochemical, rail, highways, processing, renewables, nuclear and utilities sectors. Call 01733 309500 or email info@spg.uk.net to discuss a project.
