Clay tile in Florida picks up surface algae, lichen, and mineral deposits over time. The slow accumulation is cosmetic; left untreated it becomes a visible discoloration that affects the home's appearance. Cleaning the tile is straightforward when done correctly and damaging when done incorrectly.
The wrong approach
Pressure washing at high pressure (above 1,500 PSI)
Standard residential pressure washers run 2,500-4,000 PSI. At those pressures:
- The clay surface can be eroded, particularly on older tile where the surface has weathered
- The mortar joints (if present) can be displaced
- Underlayment edges can be exposed to direct water pressure
- The cumulative cycle of high-pressure cleaning shortens tile life
We have walked roofs where multiple rounds of aggressive cleaning have produced visible wear patterns. Once eroded, the tile cannot be restored.
Bleach at full strength
Undiluted household bleach (5-8% sodium hypochlorite) damages clay tile finishes when applied repeatedly. The first application typically does no visible damage; the cumulative effect over multiple cleanings produces fading and surface degradation.
Wire brushes or aggressive scrubbing
Mechanical agitation removes surface material along with the algae or lichen. Clay tile's surface is finite; abrasive cleaning shortens the visible life of the tile.
Walking on the roof during cleaning
Wet clay tile is slippery. Cleaning typically requires applying cleaning solution and waiting; walking the roof during this period causes both worker injury risk and tile breakage.
The right approach
Low-pressure soft wash (under 1,000 PSI)
A pressure washer set to soft-wash mode, applying a dilute cleaning solution at low pressure. The cleaning is chemical, not mechanical.
Diluted sodium hypochlorite solution
A 25-30% sodium hypochlorite solution (significantly diluted from household bleach concentration), applied to the roof surface and allowed to dwell for 10-15 minutes. The solution kills algae and lichen without aggressive chemistry.
For lighter cleaning, sodium percarbonate (oxygen-based bleach) is an alternative that is gentler on tile.
Followed by low-pressure rinse
After the dwell time, the surface is rinsed at low pressure to remove the cleaning solution and the dead organic material. The pressure should be sufficient to rinse without eroding.
Treatment from the eaves up
Cleaning solution is applied from the eaves upward, allowing the solution to run down across the field. This minimizes the volume needed and ensures coverage at the lower edges where algae typically accumulates most.
Multiple light treatments rather than one aggressive
For heavily soiled tile, two or three lighter treatments over a few weeks produce better results than one aggressive cleaning. The repeated dwell allows the algae and lichen time to be fully killed and shed.
What we recommend by frequency
Annual
A light cleaning is appropriate annually in heavily shaded conditions or on roofs near mature vegetation. The accumulation does not become visible at this frequency.
Every 2-3 years
For most clay tile roofs in our service area, a more thorough cleaning every 2-3 years removes the cumulative algae and lichen that has accumulated. The cleaning takes 4-8 hours of crew time on a typical 4,000 sq ft roof.
After major debris events
Hurricane debris, mature canopy droppings, or extensive landscaping work near the roof can deposit organic material that should be cleaned within a few weeks.
What this costs
A professional roof cleaning on a 4,000 sq ft clay tile roof: $400-$900.
The cost varies by:
- Pitch (steep roofs require more rigging)
- Access (homes with tight site access cost more)
- Accumulation level (heavily soiled requires more solution and dwell time)
- Surrounding landscape (additional protection for plants)
What we will not do
Use pressure-washing without first reviewing the tile condition
Older clay tile may have weathered to where even soft-wash pressure is too much. The first cleaning visit on an older roof includes a tile-condition assessment.
Clean during conditions that increase tile breakage risk
Cold tile (rare in Florida) is more brittle. Wet tile under cleaning load is slipperier and more likely to crack. We schedule cleanings for dry conditions and mild temperatures.
Clean tile that is approaching end of life
If the cleaning would produce visible damage on an aged roof, the right answer is to defer cleaning and plan for the eventual roof refresh. We discuss this honestly during inspection.
A note on commercial cleaning services
Many homeowners use general pressure-washing services for roof cleaning. The price is typically lower than specialty roof cleaning. The trade-off is risk: general services often use higher pressure and standard cleaning solutions without considering the tile material.
For clay tile specifically — and for slate and metal — the cleaning service should be either a specialty roof cleaning company or the roofing contractor's maintenance team. The cost differential is meaningful; the risk reduction is also meaningful.
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