How can you seal horizontal expansion joints with ribbed concrete masonry units?
To seal horizontal expansion joints in concrete masonry units with ribs, I recommend installing a sealant joint flush with the plane of the unit between ribs. This will leave a space between the ribs above and below the joint. The joint must be wide enough so that it is possible to put a backer rod and tool the sealant properly between the ribs. If a joint gets too narrow, the tool will not fit between the ribs. Trying to create a sealant joint that will follow the profile of the ribs will be extremely difficult. Even if the joint could be tooled to conform to this profile, it is questionable if the joint cross-section could be maintained in accordance with the sealant manufacturer's requirements.