SPANBOIS Hybrid City Challenge


Multi-family dwellings with sprinklered below grade parking designed for pre-cast hollow core planks to form their garage ceiling and residential ground floor, can now have an ecological alternative: SpanBois prefabricated planks replace hollow core planks in a one-to-one swap. Aimed at multi-family residential construction, the SpanBois planks match hollow core planks in size and span, while greatly reducing the typical project's carbon footprint, reducing a project's cement use while increasing renewable materials (MetsäWood's Kerto-S, Kerto-QP, and birch plywood). SpanBois planks can also accommodate the typical hollow core topping, or be left exposed as a finished subfloor. SpanBois plank undersides will receive a gypsum board cover to achieve the same fire separation requirements as designs using hollow core under sprinklered and ventilated conditions. The voids in SpanBois can be filled with insulation and used as conduits - just like hollow core. And, SpanBois keyed edge profile recreates the diaphragm of grouted hollow core. Even when SpanBois modules are installed tightly, a 15 mm gap remains between plywood panel edges, allowing expansion and construction tolerances, while keeping minimum fastener edge requirements to maintain the floor diaphragm's integrity. Plank thicknesses are 248 mm for 6", 302 mm for 8", 343 mm for 10", and 440 mm for 16" hollow core.

Key benefit

Carbon footprint reduction in multi-family underground parking

Material list

Kerto-S beams
Kerto-QP beams
birch plywood

Ecological values

Substituting Portland cement-based floor assemblies with carbon capturing wood-based systems.



  • Economical span (mm) 16
  • Thickness (mm)
  • Airbourne sound reduction factor (dB)
  • Impact sound transmission (dB)
  • Resistance to fire class 2 R
  • Thermal properties



Filename Size




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