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Folkestone Grand Burstin Hotel: Post-Fire Structural Investigation & NDT Condition Assessment

Concrete Rehabilitation | NDT & Structural Scanning

Introduction & Overview

The Folkestone Grand Burstin Hotel is a prominent maritime landmark commanding Folkestone Harbour. Following a localised fire breakout within the property, client asset managers and consulting structural engineers required an urgent forensic structural investigation.

High fire temperatures cause rapid dehydrating reactions within reinforced concrete paste and thermal degradation in load-bearing structural steel. To establish whether the affected bays remained structurally sound or required propping and major intervention, Structural Repairs deployed a specialist Non-Destructive Testing (NDT) team to conduct a comprehensive condition assessment across the fire-affected ground floor and frame.

Location	Folkestone, Kent
Sector	Hospitality Commercial Leisure
Structure Type	Ribbed in-situ cast and precast concrete slab frame with integrated structural steelwork
Survey Duration	1–2 Days on site (Mobilised September 2026)

Masthead image: Folkestone from the air with the Grand Burstin Hotel in the foreground. Photo © John Fielding 2023 Flickr

The Forensic Engineering Challenge

Assessing fire-damaged structural assemblies demands rigorous diagnostic precision without inducing destructive stress into potentially compromised load-bearing elements.

The inspection confronted several complex pathology indicators:

Concrete Thermal Spalling & Dehydration: Fire exposure dehydrates calcium silicate hydrate (C-S-H) gel within the cement matrix, leading to progressive micro-cracking, internal delamination and strength loss well before surface calcination becomes visible.
Subsurface Reinforcement Vulnerability: Ribbed in-situ and precast floor slabs had to be evaluated to confirm whether cover depths shielded the rebar from yielding or unbonding during peak fire temperatures.
Structural Steel Microstructural Changes: Exposed structural steel framing and column interfaces experienced direct flame contact, risking permanent metallurgical changes, loss of yield strength and micro-flaw propagation around connections.
Hazardous Live Environment: Inspections were carried out within a restricted, soot-affected structural environment requiring strict access controls, Point of Work Risk Assessments (POWRA), full respiratory protection and zero-disturbance protocols for building services.

The Non-Destructive Testing Intervention

Operating strictly under CDM 2015 regulations, technicians applied a multi-technology NDT protocol combining subsurface radar, ultrasonic acoustics, and digital metallurgical hardness testing:

Concrete Subsurface Mapping & Cover Verification

High-Frequency Ground Penetrating Radar (GPR): Technicians scanned the ribbed in-situ and precast ground floor slabs to map embedded reinforcement layout, bar spacing, alignment and cover depth without invasive drilling.
Eddy Current Cover Metering: Precise cover depth surveys confirmed where thermal spalling had reduced protective concrete dimensions, exposing structural rebar to accelerated atmospheric corrosion.

Folkestone Grand Burstin Hotel - Concrete Subsurface Mapping & Cover Verification

Concrete Subsurface Mapping & Cover Verification

Ultrasonic Concrete Pulse-Echo & Delamination Imaging

Multi-Channel Ultrasonic Tomography: Technicians deployed an ultrasonic pulse-echo array to map internal acoustic wave reflection across the slab and columns. This technique identified hidden delaminations, fire-induced voids and subsurface concrete fracturing behind fire-scorched surfaces.
Rebound Hardness Testing: Digital rebound hammer readings were cross-referenced against ultrasonic acoustic profiles to quantify surface hardness loss and correlate in-situ compressive strength back to design parameters.

Folkestone Grand Burstin Hotel - Concrete delamination caused by fire

Concrete delamination caused by fire

Structural Steel Hardness & Flaw Verification

Leeb Dynamic Hardness Testing: Structural steel columns, beams and connection plates were prepared to remove soot and tested using portable rebound hardness probes. These hardness numbers were converted into tensile strength equivalents to verify whether intense temperatures had compromised yield properties.
Non-Destructive Flaw Testing: Key beam-to-column connections and high-stress steel junctions underwent targeted flaw detection to verify the absence of thermal cracking, weld discontinuities or heat-induced distortion.

Folkestone Grand Burstin Hotel - Concrete delamination caused by fire

Reality Capture & Survey Mapping

Spatial 3D Reality Capture: High-definition 3D spatial scanning documented the fire envelope, mapping defect locations and recording structural features to provide the client’s engineer with an exact digital record.

The Outcome & Measurable Value

Zero Destructive Disruption: By applying advanced NDT methodologies, the team avoided intrusive diamond core drilling through potentially weakened slabs, protecting the integrity of the building fabric.
Rapid Risk Verification: Completed on-site within 48 hours, delivering immediate baseline data to confirm safe zones and isolate sections requiring temporary propping.
Clear Engineering Roadmap: Findings, acoustic profiles, hardness metrics and defect coordinates were compiled into a verified engineering data report to guide remedial specifications and insurance claim settlement.

Deployed Schedule of Survey Works & Technology Suite

Survey Activity	Non-Destructive Methodology	Target Metric / Evaluation
Subsurface Reinforcement Scanning	High-Frequency Ground Penetrating Radar	Bar spacing, depth, alignment and conduit locations
Concrete Cover Verification	Magnetic Pulse-Induction Cover Meter	Rebar cover depth and spalling boundary mapping
Internal Void & Delamination Mapping	Multi-Channel Ultrasonic Pulse-Echo Tomography	Hidden internal cracking, voiding and delamination
In-Situ Concrete Hardness	Digital Rebound Hammer Testing	Comparative surface elasticity and compressive condition
Structural Steel Strength Testing	Portable Leeb Rebound Hardness Testing	Steel yield point assessment and heat-tempering check
Steel Connection Flaw Assessment	Ultrasonic & Magnetic Flaw Investigation	Weld integrity, crack detection and connection fatigue
Spatial Condition Capture	Digital 3D Photogrammetric Reality Capture	Volumetric damage mapping and structural digital record

Verify structural integrity before you commit to costly demolition.

From post-fire forensic investigation and ultrasonic concrete tomography to advanced steel hardness testing, Structural Repairs delivers non-destructive diagnostic certainty for high-value commercial assets.

Need support turning survey data into an approved remedial programme? Discover how our turnkey structural fire rehabilitation services take assets from post-incident emergency assessment through to certified handover.