Dry stack, or groutless stone veneers are becoming very popular. However, I often seem them installed poorly, and not according to the manufactuers recommendations.
In the photo on the left you, see the underlayment (blue) and and the scratch coat. In the photo on the right, you can see the scratch coat is still exposed. Also worth noting is that the installers did not use stones designed for use at the corners. The poor installation would also make me wonder what other corners they cut. Did they install 2 layers of WRB? Did they use galvanized hardware? Did they fully back butter the stones? These things are not observeable during a typical home inspection.
A dry stack installation does not use grout between the joints. Before the stones are pressed into place, the entire back of the stone must be “buttered” with mortar. As the stone is pressed into place, the mortar needs to squeeze out around the entire permiter of the stone. This ensures that no moisture can penetrate behind the stone. The stones need to be fitted tightly and the scratch coat (and definitely the underlayment) should not be visible after the installation is completed.
Look at the big whiter stone in the photo on the right. It sticks out past the small one above it. As water hits it, it may be channeled to the triangle gap on the right. The stones do not appear to have been back buttered appropriately. The water may make its way behind the stones and get trapped. If the temperature drops, and the water freezes, the expansive forces will disbond the stones.
The installer probably took the time to lay these stones on the floor first to ensure that they would fit tightly. You don’t see any large gaps. The quality of the installation would lead me to believe that the installer did everything correctly that you can’t see once the installation is finished such as 2 layers of WRB, lathe installed correctly, galvanized hardware, and fully buttering the stone.
A dry stack installation takes time and pride in a job well done. Unfortunately, we don’t see it very often.