What is the maximum lift height for hollow CMU filling (grout) if the wall exceeds 64 inches in height?

The maximum lift height for hollow concrete masonry unit (CMU) filling, commonly referred to as grouting, is determined based on the structural integrity of the wall being constructed. When a wall exceeds 64 inches in height, it is crucial to apply the proper construction practices in order to prevent issues such as cracking or excessive settlement.

The correct answer indicates that if the wall exceeds 64 inches in height, the maximum height for each lift of grout should not exceed 64 inches. This limitation helps ensure that each lift can properly bond and support the weight of subsequent layers without compromising the overall stability of the wall. Grouting too high in one lift can lead to difficulty in ensuring even distribution and compaction of the grout, which is essential for achieving the desired strength.

In contrast, the other choices suggest greater lift heights that could pose structural concerns. Therefore, adhering to the guideline of a maximum lift height of 64 inches for walls exceeding 64 inches helps maintain overall safety and structural reliability in construction practices involving hollow CMUs.