Resiliency

Wood’s strength, combined with its ability to absorb stresses or impacts without weakening or degrading, make it a superior building material in areas susceptible to severe weather conditions or seismic activity.

The overall strength of a building depends on all its components – walls, floors, roof and foundation – working together as a unit. A fully sheathed wall of plywood or OSB, properly connected to the foundation below and the roof above, creates a strong, continuous barrier against wind and seismic forces.

Laboratory tests and field evaluations show that sheathing with plywood or OSB can help make a house two to three times more able to withstand high winds and earthquakes compared to conventional construction.

High wind forces follow the load path of a structure. Good connections that tie the floor, walls and roof together provide continuity in that load path and more reliable building performance during hurricanes, tornadoes and severe wind storms.

Continuously sheathing all walls with wood structural panels – including areas around windows and doors – gives a structure an additional layer of protection if siding is lost or brick veneer collapses during high wind events.

Statistically, weaker tornadoes rated EF-0, EF-1 and EF-2 comprise 95% of all tornadoes. A home carefully constructed in accordance with current building codes and incorporating full wood structural panel sheathing can withstand these smaller but still destructive storms.

Seismic forces cause a structure’s mass to accelerate back and forth, generating forces at the roof, floor and wall lines. Wood’s light weight results in less force due to inertia during an earthquake, typically resulting in less damage to the structure.

Wood structural panels form the shear walls and diaphragms that resist lateral seismic loads, creating a rigid “box-type” structure where forces are transferred through the building into the foundation. In testing, walls fully sheathed with plywood or OSB were three times stronger than walls constructed with gypsum sheathing or let-in bracing.

Wood’s flexibility allows a building to better absorb and resist the forces found in earthquakes, making it a cost-effective and high-performing choice for seismic design.

Independent laboratory testing found that eight tested flexible structural sheathing products overstated their lateral load resistance by as much as 42% compared to their published design values. This is equivalent to a reduction of approximately 30 mph in the ultimate wind speed a structure can actually resist. In contrast, wood structural panels are required by product standards to meet or exceed 100% of their published design values.

Flexible structural sheathing products also failed to meet the seismic equivalence parameters required for light-frame walls, meaning structures built with these products could be under-designed for seismic forces. Wood structural panels meet these parameters, making them the reliable, tested choice for resilient construction in both high-wind and high-seismic zones.

Read the APA Product Advisory: Performance of Flexible Structural Sheathing (Independent Evaluations of Published Design Values), Form SP-1186 for the full laboratory results and evaluation.