When specifying façade cladding for buildings above 11 metres — or any project subject to the UK Building Regulations Part B — fire performance is non-negotiable. Glass Reinforced Concrete (GRC), also known as GFRC (Glass Fibre Reinforced Concrete), achieves Euroclass A1 — the highest possible reaction-to-fire classification under EN 13501-1:2007+A1:2009. This makes GRC cladding panels one of the safest façade materials available to architects and specifiers today.
What Is Euroclass A1 under EN 13501-1?
The European fire classification system for construction products is governed by BS EN 13501-1:2007+A1:2009 — Fire Classification of Construction Products and Building Elements, Part 1: Classification using Test Data from Reaction to Fire Tests. It defines seven reaction-to-fire classes: A1, A2, B, C, D, E, and F, with A1 being the most stringent and F indicating no performance determined.
Euroclass A1 means a product is classified as non-combustible. It will not contribute in any way to a fire — it does not ignite, does not produce flame, and does not release significant heat even when exposed to intense thermal loading. This is the classification required for rainscreen cladding on high-rise and high-risk buildings under the UK’s Building Regulations and the requirements introduced following the Grenfell Tower Inquiry.
How GRC Achieves A1 Classification — The Test Evidence
GRC’s A1 classification is not a theoretical claim — it is backed by independent, UKAS-accredited laboratory testing carried out by Exova Warringtonfire on behalf of the International Glassfibre Reinforced Concrete Association (GRCA). Both Polymer GRC and Non-Polymer GRC formulations have been independently classified.
You can find the full test reports here.
Classification requires passing two complementary test methods simultaneously:
BS EN ISO 1182:2010 — Non-Combustibility Test
This furnace test determines whether a material combusts when subjected to sustained high temperatures. Specimens are placed inside a furnace maintained at approximately 750°C and monitored over time. A material qualifies as non-combustible when:
The furnace thermocouple temperature rise (ΔTf) is ≤ 30°C
The specimen surface temperature rise (ΔTs) is ≤ 30°C
The duration of sustained flaming is ≤ 10 seconds
Polymer GRC results (Doc. Ref. 384325):
Mean furnace temperature rise: 1.2°C (limit: 30°C — result is 96% below limit)
Mean specimen surface temperature rise: 7.2°C
Duration of sustained flaming: Nil across all 5 specimens
Non-Polymer GRC results (Doc. Ref. 384326):
Mean furnace temperature rise: 1.2°C
Mean specimen surface temperature rise: 0.6°C
Duration of sustained flaming: Nil across all 5 specimens
Both formulations exhibited zero flaming at any point during testing. These figures confirm that GRC panels present no combustion risk whatsoever — a performance level far exceeding regulatory thresholds.
BS EN ISO 1716:2010 — Gross Calorific Value (Heat of Combustion)
This bomb calorimeter test measures the gross calorific potential (PCS) of a material — the theoretical maximum heat energy it could release if completely combusted. For A1 classification, the gross calorific value must not exceed 2.0 MJ/kg.
Polymer GRC results (Doc. Ref. 384329):
Gross Calorific Value: −0.0134 MJ/kg
Non-Polymer GRC results (Doc. Ref. 384330):
Gross Calorific Value: −0.3877 MJ/kg
Negative calorific values indicate that GRC panels actually absorb energy in a calorimetric sense — they release effectively zero combustible energy. The A1 threshold is 2.0 MJ/kg; GRC returns values of −0.01 and −0.39 MJ/kg respectively — orders of magnitude below the limit.
GRC Fire Classification at a Glance
Source: Exova Warringtonfire (GRCA), Test Reports 384325/26/29/30, June 2017
Why A1 Matters for Your Project
High-Rise & High-Risk Buildings
The UK government’s response to the Grenfell Tower disaster fundamentally changed requirements for external wall systems. Buildings above 11 metres in height now require that external cladding systems achieve at minimum Euroclass A2-s1, d0 — with many planning authorities and developers requiring the higher A1 standard for full peace of mind. GRC cladding satisfies the strictest interpretation of these requirements without compromise.
Building Regulations Part B (Fire Safety)
Under Approved Document B, external wall materials on relevant buildings must be of limited combustibility or better. Class A1 exceeds this threshold — it is the only classification that the Government’s own technical guidance describes as “non-combustible.” Specifying A1-rated GRC panels removes any ambiguity from your fire strategy documentation.
No Flame Retardant Additives Required
A key differentiator of GRC is that its A1 performance is intrinsic to its mineral composition — no flame retardant additives are used in the production of GRC. The matrix of Portland cement, alkali-resistant glass fibres, fine aggregate, and water is inherently non-combustible. This means there is no risk of additive degradation over time, no concern about the fire performance of the product changing after installation, and full confidence in long-term performance.
Insurance, Warranty & EWS1 Confidence
EWS1 (External Wall Survey) forms — required by mortgage lenders and insurers for many residential buildings — demand evidence of fire-safe cladding. GRC panels with documented A1 certification provide building owners and leaseholders with one of the clearest, most unambiguous routes through the EWS1 process. UKAS-accredited test reports from an independent notified body (Notified Body No. 0833) provide the level of documented evidence that fire engineers and assessors require.
GRC vs Other Cladding Materials — Fire Performance
GRC panels combine the A1 fire rating of traditional masonry with the lightweight versatility and design freedom of modern manufactured panels — making them the preferred material for projects where fire safety, aesthetics, and structural efficiency must all be satisfied simultaneously.
GRC Fire Rating FAQ
Q: Is GRC the same as GRC concrete in terms of fire performance?
Yes — GRC (Glass Reinforced Concrete) and GFRC (Glass Fibre Reinforced Concrete) are the same material described by different terminology used in different markets. Both terms refer to an alkali-resistant glass fibre reinforced Portland cement composite, and the A1 classification applies to both polymer-modified and non-polymer GRC formulations.
Q: Does GRC’s fire classification cover all thicknesses?
The classification reports cover GRC at the tested thicknesses (Polymer GRC: 46.09mm; Non-Polymer GRC: 45.95mm) and at the tested densities. Any variation in thickness or density outside these parameters would require re-evaluation. Always confirm panel specifications against the certified test parameters with your GRC supplier.
Q: What is the difference between Polymer GRC and Non-Polymer GRC for fire purposes?
Both achieve A1. Polymer GRC incorporates polymer additives (typically acrylic) which improve flexural strength and workability; these additives are present at low enough levels that they do not affect the fire classification. The calorific test results confirm both formulations fall well below A1 thresholds.
Q: Can GRC be used as the outer leaf on an EWS1 building?
Yes. UKAS-accredited A1 certification from a notified body (such as Exova Warringtonfire, Notified Body No. 0833) provides the evidential documentation required for EWS1 Form B (or Form A where the entire system is non-combustible). Consult your fire engineer for system-level assessment.
Specifying GRC Cladding for Fire-Safe Façades
When specifying GRC panels for projects where fire performance is critical, request the following documentation from your supplier:
EN 13501-1 Classification Report — confirming Euroclass A1 (not just a product data sheet claim)
EN ISO 1182 test report — non-combustibility furnace test results
EN ISO 1716 test report — gross calorific value bomb calorimeter results
Notified Body certification — UKAS-accredited, independently issued
DoP (Declaration of Performance) — under CPR (Construction Products Regulation), confirming fire class
GRC manufactured to GRCA (International Glassfibre Reinforced Concrete Association) specification and tested in accordance with the above standards provides architects, contractors, and building owners with the highest level of fire safety assurance available for a façade cladding product.
It’s worth to mention that the fire classification was provided for the GRC panels only without surface coating. Therefore, project specific assessment has to be carried out by a competent engineer to consider the actual system as a whole.
As noted by the GRCA”Always verify the specific manufacturer’s certification documentation, as exact test metrics can vary depending on the specific additives and production methods used.”