Q: I have a wall system with multiple windows spaced closely together with arches. As a result, the pier between the windows is only 32-in. wide. The wall is about 80-ft long. Obviously I need expansion joints in the 80-ft length of masonry above these arched windows.

Where should I install the expansion joints?

A: It is very difficult to install expansion joints when the arch openings are closely spaced. There are basically two approaches for providing expansion joints at walls containing multiple arched windows.

The most common is to place the expansion joint in the pier between the adjacent arches (Fig. 1). However, since the pier is only 32-in. wide, there probably will not be enough masonry adjacent to the expansion joint to resist the lateral thrust of the arch.

The expansion joint cannot be placed within a true arch itself since the arch relies on compression to carry load to the masonry on each side. An expansion joint, by its very definition, disrupts this region of compression, which would cause the arch to fail.

One solution is to use curved steel angles to support the masonry at some of the arched openings to permit the installation of expansion joints, as illustrated in Fig. 4 in Technical Note 31 (Fig. 2 here). A joint can be installed at the apex of these false arches since they are no longer structural (Fig. 3).