Hollow Spots in Flexible Stone: Why They Happen and How to Prevent Them

Hollow spots in flexible stone are air pockets left between the panel and the wall when adhesive is applied unevenly. They expand and contract with temperature changes, weaken the bond, and can lead to delamination over time. This guide explains the causes of hollow spots and the application technique that prevents them.

What Causes Hollow Spots

Hollow spots form when the adhesive does not make full contact with the back of the panel. Common causes are dot-and-dab application, too-thin adhesive, missed edges, and uneven pressure when pressing the panel onto the wall. Each air pocket is a weak point that expands and contracts with temperature, slowly working the bond loose.

Why Hollow Spots Matter

A hollow spot is not just a cosmetic defect. The trapped air moves with temperature changes, stressing the bond line around it. Over time, hollow spots grow and can merge into large areas of delamination. Contractors often detect them by tapping the wall and listening for the hollow sound - by then, the fix means removing and reinstalling the panel.

The Correct Application Technique

1. 1Apply the flexible adhesive with a notched trowel for full, uniform coverage.
2. 2Cover the entire back of the panel - do not spot-bond or dot-and-dab.
3. 3Press the panel onto the wall with consistent, even pressure across the full surface.
4. 4Roll the panel with a roller to seat the adhesive and push out trapped air.
5. 5Check for voids by tapping the installed panel before the adhesive cures.

How Fast Can You Install Flexible Stone

Because flexible stone is only 2-4 mm thick and bonds with full-surface adhesive, full-contact installation is easy to achieve. Two installers can clad a 25 m² room in a single day with zero rework - compared with 8-10 m² per day for natural stone. The thin profile is exactly what makes a void-free bond practical.