Timber floor (beams and planking)

The traditional timber floor: parallel beams carrying a board decking, on which the completion layers rest. Light, warm and renewable, it is the floor of historic buildings and today returns in new dry construction. Its strength comes from the bending of the beams; the points to manage are deflection (springiness), vibration, acoustics and protection from fire and moisture, today resolved with a topping or structural deck and resilient layers.

The timber floor is made of parallel beams, of solid or glulam timber, that span by bending under the loads; over them, a board decking (or panels) forms the plane and spreads the loads onto the beams. It is the oldest and most widespread floor in historic buildings, and today, in dry timber construction, it is again a protagonist for its lightness and sustainability.

Under load the beam bends: the top fibres go into compression, the bottom into tension, and timber — light but not very stiff compared with steel or concrete — tends to deform. More than strength, deflection often governs: a timber floor must be checked so it does not «bounce» or sag too much. Hence beams are made deeper and closer, or the decking is made to collaborate.

Being light, the timber floor easily transmits impact noise and can vibrate underfoot. The care is in the layers: a screed (even dry) that adds mass, a resilient layer that decouples the floor finish from the structure, and fibrous materials in the cavity between the beams. Mass and decoupling, not timber alone, give the acoustic comfort.

Timber burns, but predictably: a charred layer forms and protects the core, so the beam keeps strength for a calculable time (it is oversized for fire). The real enemy is moisture: beam ends built into damp masonry that rot, leaks, insects. The bearings are protected (ventilated, not in direct contact with damp masonry), moisture is controlled and the surfaces are treated.