MAGNUMBOARD® OSB // HybridWood passes F90 fire test

Innovative solid wood-and-concrete composite ceiling delivers safety and efficiency

The standardised fire test, carried out at ift Rosenheim in November 2025, confirmed that the solid wood-and-concrete composite ceiling achieved 90 minutes of fire resistance under simultaneous full load. SWISS KRONO now offers highly efficient solid OSB/4 floor elements with reinforced concrete ribs for large spans that meet the most demanding requirements in terms of fire protection, load-bearing capacity and economical construction.

During the test, the 210 mm-thick HybridWood floor 'MB-O 210' was exposed to temperatures of up to 1,000°C from below for 90 minutes while being loaded from above with 4 kN/m².

Test results at a glance:

• 90 minutes of fire resistance (F90 / REI90)
• Load-bearing capacity maintained
• Surface temperature of the slab on the concrete side remained unchanged
• Underside of the slab (MAGNUMBOARD® OSB): of the total 125 mm MAGNUMBOARD® OSB thickness, approx. 70 mm were charred. The solid wood forms a protective char layer during a fire, insulating the underlying material and slowing further charring.

This demanding test procedure demonstrated that, in the event of fire, the construction not only remains structurally stable, but the upper surface of the slab shows no relevant temperature increase – a key factor for life safety.

Also tested: wall connection with PhoneStrips

Another important part of the test was the floor-to-wall connection, which was also tested using PhoneStrips. For acoustic decoupling, 15 mm-thick PhoneStrips (2 × 50 mm and 100 mm wide) from Wolf Bavaria were used. These connections achieved 90 minutes of fire resistance. This demonstrates that the acoustically decoupled joint, as well as the floor element itself, performs safely in the event of a fire.

What do these results mean for practice and design?

The positive test outcome goes well beyond mere compliance with standards:

• Real safety in the event of a fire. The very low temperature on the upper side means that emergency responders could, in theory, walk across the upper floor barefoot to rescue people – a striking illustration of the system’s protective performance.
• Economic advantages: Due to its lower self-weight of approximately 3 kN/m² (compared to approximately 5 kN/m² for conventional concrete slabs), thinner wall thicknesses can be designed, resulting in cost savings and additional usable floor area.
• Material synergy: in the event of a fire, the wood acts as a natural thermal barrier, protecting the concrete and the reinforcing steel inside from overheating.

Thanks to its performance parameters, MAGNUMBOARD® OSB // HybridWood is suitable for a wide range of construction applications — from multi-storey residential and commercial buildings to schools and hotel projects, as well as demanding structures with large spans.

Visit us at Dach+Holz in Hall 7, Booth 506. We would be happy to explain the product to you at our exhibit.