For buildings with a roof pitch of less than what ratio must hips and valleys be designed as beams?

In residential building construction, the design of hips and valleys is critical to ensure adequate structural support, particularly as the pitch of the roof decreases. A roof pitch of less than a 3:12 ratio indicates a low-sloped roof, which significantly alters how the weight and stresses are distributed across the roofing system.

When the pitch is lower, the roof does not effectively shed water and may be more susceptible to strain from snow loads or high winds. Therefore, it requires additional support to prevent sagging or structural failure. By law or building codes, when the pitch is below this threshold, the hips and valleys must be designed and considered as beams. This is because, at lower pitches, the typical rafters may not provide enough strength on their own, thereby necessitating a design that can adequately support the additional loads.

The option identified as correct emphasizes the importance of structural integrity at lower pitch ratios, enabling builders to construct safe and reliable residential structures.