Do I need fire insulation?

This guide sets out what fire insulation actually is, the three types of product that sit under that heading, what each one does in a fire, and how to work out whether your project needs any of it. No product pitch: just the information you need to specify correctly.

What "Fire Insulation" Actually Means

There is no single property called "fire rating". There are two, they are measured by different tests, and they are constantly confused with one another.

Every standard gypsum plasterboard on the market, including the fire resistant grades, is A2-s1,d0. Only a smaller group of boards, generally calcium silicate, fibre cement or gypsum fibre, achieves A1.

What Changed in 2025, and What Changes in 2029

For decades the UK ran two parallel fire testing systems: the national BS 476 series, which produced terms like "Class 0" and "Class 1 surface spread of flame", and the European BS EN 13501 series, which produces Euroclass ratings. Following the Grenfell Tower Inquiry and a consultation that ran from December 2022 to March 2023, the government confirmed in September 2024 that the national classes would be withdrawn from Approved Document B.

Transitional arrangements apply throughout, so earlier editions continue to apply where a building notice, initial notice or full plans application was made before the relevant date and the work started and was sufficiently progressed before that day or within six months of it.

The practical effect for anyone buying today: "Class 0" is no longer a compliance route in England. Some products still carry it in their name, because that is what the manufacturer called them, and some still hold genuine BS 476 test evidence. Neither of those things makes it a route to satisfying Building Regulations now. If you are specifying to Approved Document B, you need a BS EN 13501-1 classification, and if the supplier cannot show you one, that is your answer.

The Three Types, and What Each One Is For

"Fire insulation" gets used as a catch-all for three genuinely different product groups.

Fire Resistant Plasterboard

Gypsum boards manufactured to BS EN 520 Type F. Type F means the gypsum core contains mineral fibres or other additives that improve core cohesion at high temperatures.

The mechanism is worth understanding, because it explains what you are actually buying. Standard plasterboard already performs reasonably in fire: the water chemically bound into the gypsum core absorbs heat as it is driven off, which buys time. The problem is what happens next, when the dried-out core crumbles and stops shielding what is behind it. The glass fibre in a Type F core holds the board together through that stage, so it keeps protecting the structure for longer.

These boards are almost always pink-faced so they can be identified on site, they are A2-s1,d0, and they are the volume end of the category: separating walls, corridors, integral garages, protected stairways, loft conversion ceilings and partitions. Moisture resistant versions are available for intermittently humid rooms such as bathrooms, kitchens and plant rooms, and duplex versions carry a metallised polyester film on the reverse so a fire board and a vapour control layer go up in one fixing operation. See the full fire resistant plasterboard range.

Fire Protection Boards

A different class of product for higher-performance and specialist duty: structural steel encasement, shaft walls, ductwork, service risers, mezzanines and plant rooms. Rather than paper-faced gypsum, these are calcium silicate, gypsum fibre or fibre cement. They are generally A1 non-combustible, considerably denser, considerably more expensive, and rated for longer periods.

Three things make them worth the money where they are specified:

• No contribution to fire load. Which is why they have become the specification default on higher-risk work.
• Moisture stability. Several of them can go in early, before the building is weather-tight.
• Longer sheets. Some are supplied at 2600mm and above, which removes horizontal joints at standard floor-to-ceiling heights. A labour saving and an integrity gain on a fire rated wall.

Within this group you will also find frameless encasement systems for structural steel, where the board is fixed directly around the section with no metal framing. That cuts labour and takes up less space than a framed encasement, but the period achieved depends on both board thickness and the section factor (A/V, or Hp/A) of the steel. That is a calculation, not something a thickness alone guarantees. Browse the fire protection boards range.

Fire Resistant Insulation

This is the one most people mean when they type "fire insulation": non-combustible or limited-combustibility mineral wool that fills the cavity inside a fire rated construction.

It does three jobs at once. It slows heat transfer through the build-up. It stops convection currents carrying heat around inside the cavity. And in most tested partition, floor and separating wall systems it is a required component rather than an optional upgrade, with both density and thickness specified by the test.

It is also doing acoustic duty at the same time, which is why a single slab so often appears in both an Approved Document B and an Approved Document E solution. Rockwool RWA45 at 45 kg/m³ and 0.036 W/mK is the default choice for exactly that reason: one product, two boxes ticked. See the full fire resistant insulation range.

So Do You Actually Need It?

Work through these in order.

• You are building or altering a separating wall or floor between dwellings, or between a dwelling and an integral garage
• You are forming a protected stairway or escape corridor
• You are converting a loft, where the ceiling below usually needs to achieve a specified period
• You are building flats, HMOs, student accommodation or commercial fit-out, where a period will be specified
• You are encasing structural steel that needs to keep its loadbearing capacity for a set time
• Your drawings, Building Control officer, warranty provider or fire strategy specify a period. If a number in minutes appears anywhere on your paperwork, that is the answer.

• Home offices, garden rooms and outbuildings near a boundary, where separation distances come into play
• Plant rooms, boiler cupboards and anywhere with a solid fuel or biomass appliance
• Any project where you are also solving a noise problem in a wall or floor, since mineral wool covers both and the cost difference against a non-rated alternative is small

• A straightforward internal stud partition inside a single dwelling, with no separating function and nothing specified
• Standard loft insulation at ceiling level in an unconverted roof space
• Refreshing existing linings where you are not altering the construction

Five Things That Decide Whether It Performs

Specifying the right product and then installing it loosely is the most common way to fail an inspection.

Four Claims to Be Sceptical Of

• "Fireproof." Nothing on this site, or anyone else's, is fireproof. Products are classified for how they react to fire, and constructions are tested for how long they hold out. Both are measured in minutes and classes, not absolutes.
• "A2-s1,d0 means non-combustible." It does not. A2 is limited combustibility. A1 is non-combustible. The distinction is written into Regulation 7(2), which requires materials becoming part of an external wall, or a specified attachment, of a relevant building to be A2-s1,d0 or A1 to BS EN 13501-1.
• "This board is 60 minute fire rated." A board cannot be. Ask which system it was tested in, and ask for the report reference.
• "Same thickness, same board." Boards from different manufacturers are not interchangeable within a tested system, even at identical thicknesses. If the test named a board, that is the board.

What We Stock

Grouped by the three categories above. Note what is not shown against any of these: a period in minutes. That figure belongs to the system, not the board.