Limitations

Like any other structural system, wood bearing walls do not come without drawbacks. Outlined below are some of the limitations associated with wood-framed construction.

Elastic Modulus - Is a ratio of stress to strain for any material and is a measure of the material's stiffness. Constructrion grade lumber typically ranges from 5,000-17,000 MPa (104 million - 355 million pounds per square foot). When the load reaches this point, the member will fail.

Moisture Condition - Wet timbers greatly reduce the strength of the material. It is very difficult to keep lumber at a constant moisture condition. Some builders will allow the lumber to dry before using it because if it dries after drywall and sheathing has been added it will cause movement within the walls and cracking will result.

Timber Size - The length of a timber depends on the tree it was harvested from. It can be very difficult to get lengths of over 90 feet, which limits the size of spans/walls in a building unless addition supports such as steel is added.

Environmental Concerns - As a material, wood can be hard to come by in certain regions, making it incredibly expensive. In areas prone to earthquakes and or flooding, wood is also not a good choice as it will be subject to failure under seismic loads. In flood zones wood becomes a habitat for mold to grow and will eventually rot and lose strength if not properly dried.

Temperature Variants - Significant temperature changes can cause some residual moisture in the wood to evaporate very quickly and cause cracking. Depending on the severity, this could result in a structural failure or cracks in drywall/sheathing. Roof trusses in attics are especially prone to such cracking due to poor ventilation in some attic spaces, large solar heat loads, and the heat rising from the floors below.