The Best Caulking Material for Vertical Masonry Expansion Joints

The strength of the wall is dependent on the type of mortar and the quality of the assembly.

Masonry Wall Expansion

Masonry walls expand and contract dependent on the temperature and moisture content. Like almost all elements on the planet, masonry walls will expand as the temperature increases and contract as the temperature drops. Moisture will have the same effect on a masonry wall. The more moisture present, the more it will expand.

Expansion Control Joints

To control the expansion and protect the wall structure from cracking under pressure, masons install vertical control joints at specific locations. These joints will absorb the pressure created by the expansion by giving the masonry wall flexible space to expand.

Types of Caulking

There are a number of exterior caulking options which will work in masonry. The most important characteristics are an exterior type, adhesive ability and flexible. While almost all exterior caulking will work for this application, polyurethane is the most commonly used because it is superior to latex and silicone caulking in these qualities.

Application

Control joints are filled by placing a polyurethane foam rod into the crack to provide support for the caulking. Then apply the necessary amount of caulking on top of the foam rod. It is best to cover the gap is one single application rather than several passes.