Why You Should Never Power Wash Your Concrete Tile Roof

Concrete tile roofs are valued for their durability and long lifespan. However, many homeowners may overlook the risks associated with pressure washing as a cleaning method. While it may seem like an efficient way to remove dirt, moss, lichen, and algae, pressure washing can cause significant damage to your concrete tile roof. 

Most homeowners understand that their concrete tile roof should last a lifetime. After all, It’s concrete! While it is true that some clay tile roofs last a hundred years or even more, this is not the case with concrete tile. Most existing concrete roofs are actually “lightweight” concrete tiles. It is not the same as a concrete porch or driveway. 

So, is power washing, the long-time go-to solution for exterior cleaning, the proper approach to cleaning a concrete tile roof? NO!

Why? Power washing a concrete tile roof causes irreversible damage in several ways.

1. Irreversible Damage to Tile Finish

Nearly all concrete products have a smooth finish. This is because the concrete is worked to bring up the ‘fines,’ the Portland cement, and often the color-producing oxide (pigment). The finish hides the structural component of the concrete, which is the aggregate, rock, and sand. In the case of concrete tile, just sand.

Using high pressure to clean concrete tile, removes the fines from the outer layer of the tile, exposing the aggregate (the sand). In so doing, it removes the color of the tile. The result, aesthetically, is that the new color becomes the freshly exposed aggregate (sand) used to make the tile. The damage caused is irreversible. The color cannot be restored.

2. Increased Porosity and Moisture Retention

The goal of cleaning a concrete tile roof is to have a clean, aesthetically pleasing appearance, free of biological growth such as bacteria, algae, moss, and lichen. Power washing a concrete tile roof removes the smooth finish. It leaves a far more porous, absorbant, unsealed surface that retains moisture.

Moisture is always the basis for the biological growth on roofs. (This is why the ‘dirtiest’ areas on roofs are always the north-facing facets, which receive little to no direct sun exposure or are highly shaded areas). The result of this new moisture-retaining surface is that the tile becomes ‘dirty’ with new biological growth much quicker. The need for successive power washing increases. Each cleaning exposes more of the aggregate, removes more of the finish (the color), and exacerbates the problem, creating the need for even more cleaning.

3. Uneven Cleaning and Tile Surface Damage

Power washing, as a method to clean a tile roof requires using nozzle tips at a consistent distance from the tile surface to attain a comprehensive, uniform appearance of the entire surface. This is functionally impossible and often leads to inconsistent wand strokes and damage to the tile surface.

Surface cleaners are frequently touted as the solution to this problem. However, surface cleaners are designed for flat surfaces. Roofs are not flat, so surface cleaners cause even more damage. Using power washing equipment to clean concrete tile roofs also requires accessing the entire roof, covering every square inch of the tile surface. This leads to more broken tile, not to mention the damage caused to mortar joints, often found at hips and ridges.

Conclusion

While pressure washing might seem like a quick fix for cleaning your concrete roof, the potential damage it can cause is significant and irreversible. From surface erosion to moisture penetration. The risks far outweigh the benefits. 

The safer solution is a detergent-based, non-pressure cleaning method. This process kills all biological growth. It leaves a consistent, clean appearance and produces results that last far longer than power-washing.

Ready to protect your concrete tile roof? Call Pacific Exterior today at (831) 250-9938 for a free estimate or schedule a service online for safe, effective, and long-lasting roof cleaning solutions.