I noticed a small space between this brick and the mortar underneath it on my front porch. It’s wide enough for me to fit a piece of old duct tape into the gap. I’m not sure when it was repointed last. The house itself is 101 years old. Is this cause for concern? If so, what is the right fix?
It is such a small space and the rest of the mortar looks to be in great shape so I'd look at sealing the crack with a concrete crack and masonry sealant. Start out by pressure cleaning or scrubbing the mortar to get rid of the mildew. Once dry, get a sealant similar to the one shown below that's a close match to your mortar color. Don't cut the tip off like you'd normally do because the hole will be too big. Puncture the tip with a finishing nail and squeeze the sealant into the cracks. Run a utility knife blade in the crack to widen it just a bit before applying the sealant.
Picture is from the Lowe's web site