We have compiled a glossary of common masonry and tuckpointing terms to help you make informed decisions about your next masonry project. If you have any questions or want to put our decades of experience to work for you, contact us!
A collar joint is an intentional gap between multiple wythes of a masonry wall.
Builders of newer masonry buildings like to leave a gap of 1" - 3" between the brick wythes (or between the brick wall and the concrete block back-up wall) in order to prevent wind-driven rain from more readily passing through the wall and reaching your finished interior living space. The common thinking is that precipitation which penetrates the outer wythe of brick can't leap across the collar joint and work its way toward your interior walls.
In the photo below, AAA-1 Masonry & Tuckpointing has just removed the capstones from an existing parapet wall. The photo was taken from above in order to easily see the cross section of the wall. This parapet wall was constructed with two wythes of brick with a large collar joint between them.
The idea behind the use of collar joints is a good one. In theory, it does seem impossible for water to jump across a 1" - 3" gap and reach the interior living space. In reality, however, masonry restorationists shudder at the sight of collar joints because this gap prevents the two wythes of brick from being tied together in any meaningful (read: structural) way. When each wythe of brick is separated by a collar joint, the wall is not nearly as strong nor as laterally stable as if the two wythes of brick were built right up against one another (i.e., built without a collar joint) like older masonry construction.
So, then, why do builders use collar joints?
Our best guess is that it is because the architects who design these building and the masons who erect them are the not the same designers and masons who repair them years later. Ask a quality architect/engineering firm like Enspect or Perry & Associates and you'll get a great education as to why the tried and true method of masonry construction from the last century is the longest-lasting method of masonry construction.