Epic design lead Eric Williamson (Reddit handle u/EpicEricSW) broke news on the r/FortniteBR subreddit today by confirming that a fix for walls being built partially underground is coming in patch 7.20.
This has been a long-term issue, with complaints first popping-up on Reddit and the Epic forums more than a year ago. Williamson introduced a logical approach to solving the problem, when attempting to place a wall that requires a connecting piece and is at least 70% underground the piece will be built automatically and at no material cost. The connecting piece will be editable by team members and will be built of the same material as the originating piece.
Williamson goes on to clarify in the comments that this fix currently applies to wall pieces only, but hints that it could be applied to other build pieces in the future.
Below is the Reddit post in it’s entirety, complete with GIF’s that visually clarify how the change will be implemented.