What is a key factor to consider in the design of CMU foundation walls?

When designing concrete masonry unit (CMU) foundation walls, a key factor to consider is the damp-proofing of the exterior walls. This is crucial because foundation walls are typically in contact with soil, which can introduce moisture that may lead to problems like mold growth, structural damage, or reduced insulation effectiveness over time.

Damp-proofing helps to prevent water from penetrating the wall, thereby protecting the structural integrity of the masonry and enhancing the longevity of the building. Proper damp-proofing methods, such as applying waterproof membranes or sealants, are essential to ensure that moisture does not compromise the foundation.

In contrast, while structural load capacity is also important in overall wall design, it pertains more to the walls' ability to support the building rather than the specific risks associated with moisture. The color of the masonry and the thickness of the mortar, although they can have aesthetic and construction quality implications, are not critical factors compared to the necessity of ensuring a moisture-resistant foundation.