Why Gaps Form Between Roof Tiles and Walls—and How to Fix Them
- Bill Horton
- Nov 20
- 1 min read
Have you noticed a gap forming where your roof tiles meet the wall of your home? This is a common issue in Arizona homes, especially with tile roofs. At first, the joint may look sealed with mortar, but over time, gaps can appear—sometimes as wide as ¾ inch.
Why Does This Happen?
Several factors contribute to this problem:
Thermal Expansion and Contraction Arizona’s extreme temperature swings cause roof tiles and stucco walls to expand and contract at different rates. Rigid mortar can’t flex, so it eventually separates.
Structural Movement Homes settle over time, and roof framing can shift slightly. Even small movements break the bond between mortar and tile.
Weathering and Moisture Rain, irrigation splash, and wind-driven dust erode the joint. If water gets behind the mortar, it accelerates deterioration.
Why Mortar Isn’t the Best Choice
Mortar is strong but rigid. It’s not designed for joints that experience movement. Over time, cracks form, and the joint fails. The correct approach is to use a flexible, weather-resistant sealant that can handle expansion and contraction.
The Right Solution
Remove the Old Loose Mortar Carefully chip out any loose mortar without damaging the tiles or stucco.
Clean the Joint Brush out debris and ensure the surface is dry.
Apply a Flexible Sealant Use a high-quality exterior-grade sealant—polyurethane or silicone-based—for maximum durability. These products are UV-resistant and designed for roofing applications.
Tool the Sealant for a Neat Finish Smooth the bead so it adheres well and looks clean.
Benefits of Doing It Right
Prevents water intrusion
Maintains roof integrity
Handles Arizona’s extreme heat without cracking
Improves the appearance of your roofline