What counts as non-reactive fire protection
Non-reactive fire protection (known in CIS terminology as “constructive” fire protection) is protection that works through its own thickness and insulating properties rather than through a chemical reaction. It is a layer of material that stays in place during a fire and prevents heat from quickly reaching the steel or the reinforcement. This group includes:
- spray- and trowel-applied plasters — cementitious, cement-vermiculite, gypsum and gypsum-vermiculite products;
- boards — calcium silicate boards, plasterboard and gypsum fibre boards, mineral wool fire protection boards;
- mats and wraps — wired mineral wool mats (stitched to wire mesh), foil-faced basalt and ceramic fibre rolls;
- masonry and concrete encasement — the traditional method in which the steel is enclosed in brickwork or concrete; today it is used less often because of its weight and labour intensity.
The two main groups are covered in detail on the “Fire protection plasters” and “Fire protection boards and mats” pages.
Where non-reactive fire protection has the advantage
- High fire resistance ratings. At R 120 and above, the thickness of intumescent paint increases, and its cost with it. In such cases boards or plaster often prove cheaper and easier to inspect.
- Concealed structures. If the steel is hidden above a suspended ceiling or behind a lining, the appearance of the protection does not matter — the most economical option can be chosen.
- Severe mechanical exposure. Dense plasters and calcium silicate boards stand up better to impact in car parks, workshops and warehouses.
- Difficult application conditions. Boards are installed “dry” and can be fixed in weather in which paint cannot be applied.
- Multiple functions. Mineral wool boards provide thermal and acoustic insulation at the same time, while calcium silicate boards can form self-supporting fire-resisting enclosures, shafts and partitions.
How it works
The principle is simple: the heat flux from the fire has to pass through a layer of material with low thermal conductivity, so the steel heats up more slowly. Many materials add heat absorption to this: gypsum and some boards contain chemically bound water, which evaporates when heated and “soaks up” part of the energy. Vermiculite — exfoliated mica — is a lightweight, heat-resistant filler that reduces the density and thermal conductivity of the plaster.
How to choose a solution
Fire resistance rating and element type
Manufacturers provide separate thickness tables for columns, beams, bracing and floor slabs. The calculation differs between box encasement with boards and plaster applied to the profile: a box has a smaller heated perimeter, so the required thickness may be lower.
Reduced metal thickness
As with paints, the key parameter for steel is section massivity. The lower the ratio of heated perimeter to area (Hp/A), the slower the heating and the thinner the protection required.
Environment and durability
Gypsum plasters are intended for dry interiors. Cementitious products and calcium silicate boards tolerate humidity, and certain grades also withstand external exposure and oil and gas fire scenarios. Mineral wool boards need protection against mechanical damage and direct wetting.
Weight and load on the frame
Dense cementitious coatings and concrete encasement add significant weight to the structure. For lightweight frames and refurbishment projects, this may be the deciding argument in favour of boards or paint.
Compatibility with corrosion protection
Under plaster, steel is primed with a product approved by the plaster manufacturer: some primers impair adhesion, in which case mesh or a special bonding coat is required. Under boards, the primer is needed primarily to protect against corrosion throughout the service life.
Common mistakes
- Applying plaster to an unprepared or wrongly primed surface — it delaminates the first time it is heated.
- Cutting corners on board fixings and joints: fire finds the gap and the system fails.
- Gypsum-based products in unheated and damp areas.
- Failing to protect mineral wool materials from damage and wetting while building services are being installed.
- Sections of protection removed by other trades and never reinstated.
Materials from leading manufacturers
- CAFCO 300 / ISOLATEK Type 300 — Isolatek International — spray-applied gypsum fire protection for beams, columns and floor slabs.
- PROMASPRAY-P300 — Promat — vermiculite-gypsum plaster for steel and concrete inside buildings.
- Promat FENDOLITE MII — Promat — cement-vermiculite coating for external and oil and gas applications.
- Pyrocrete 241 — Carboline — Portland cement-based fire protection for heavy industry.
- PROMATECT-H — Promat — calcium silicate board for encasing steel, lining concrete, and for shafts and partitions.
- PROMATECT-L500 — Promat — low-density board for fire-resisting ductwork and enclosures.
- ROCKWOOL Conlit 150 — ROCKWOOL — rigid stone wool boards for fire protection of load-bearing structural steel.
- ROCKWOOL Conlit Fire Mat — ROCKWOOL — wired mat (stitched to wire mesh) for circular ductwork.
Frequently asked questions
Which is cheaper: paint or boards?
There is no single answer. For low ratings and exposed steel, paint usually wins; for high ratings and concealed structures, boards or plaster do. What should be compared is the installed cost of the complete system, not the unit price of the material.
Can paint and boards be combined on the same project?
Yes, this is common practice: for example, visible columns are painted, while beams above the ceiling are boarded. What matters is that each element has its own approved solution.
Does non-reactive fire protection need maintenance?
Less than paint does, but inspection is still needed: check that the layer is intact, with no chipping, no wetting and no areas left opened up after repairs to building services.