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Mastering the Art of Slate Roof Maintenance: Step-by-Step Guide on How to Clean a Slate Roof

While slate roofs are superior to other roofs in terms of lifespan, they are not without the need for occasional maintenance. Cleaning and maintaining a slate roof is essential to ensure its longevity and beauty. Here is a step-by-step guide to help you master the art of slate roof maintenance:

How to Clean a Slate Roof

Prepare the Roof


1. Safety first: 

Before starting any work on the roof, make sure you have the necessary safety equipment, including a sturdy ladder and scaffolding.

2. Inspect the roof: 

Begin by visually inspecting the entire roof for any visible damage, such as cracked, loose, or missing slates. Note down any repairs required for later.

3. Trim back tree branches: 

Overhanging tree branches provide shade and moisture that can encourage algae and moss growth. Trim back any branches that are too close to the roof to reduce the amount of shade and dampness.


Clean The Slate


moss on slate roof

4. Remove debris: 

Begin by removing any leaves, dirt, or other loose debris from the roof surface. A light leaf blower can be helpful at this stage. You can also use a brush or broom. Do not use a heavier broom to avoid damaging or dislodging slates while completing this step.

5. Choose a cleaning solution: 

Use a gentle cleaning solution specially formulated for slate roofs. Avoid using abrasive chemicals or high-pressure washers, which can damage the slate. You may have to research to find the best cleaning solution. Hydrogen peroxide tends to be gentle and shouldn’t harm surrounding vegetation, but it may not be strong enough for tough stains or algae. When using chemicals, read the instructions carefully and use appropriate safety measures. Wear gloves and goggles to protect yourself from splashing and overspray. 

6. Wet the roof: 

Spray the cleaning solution using a low-pressure sprayer attached to a garden hose over a small roof section. Working in small areas is vital to prevent the solution from drying before rinsing it off.

Scrub, Rinse & Repair


clean slate roof


7. Scrub the slate: 

Using a soft-bristle brush or a gentle scrubbing pad on a pole, lightly scrub the slates in a circular motion to remove any dirt or stains. Take care not to apply too much pressure to prevent damaging the slates.

8. Rinse off the cleaning solution: 

After scrubbing a section, thoroughly rinse the area with clean water using the sprayer. Ensure all traces of the cleaning solution are removed.

9. Repeat the process: 

Continue working in small sections, repeating steps 5 to 7 until the entire roof is cleaned. It’s important to avoid letting the cleaning solution dry on the rooftop, as it can leave behind a residue.

10. Inspect and repair:

Once the roof is cleaned, inspect it for any damage or repairs needed. Have any cracked or missing slates or loose or damaged flashing fixed?


Prevent Unnecessary Cleaning


11. Preventive measures: 

Consider installing zinc or copper strips along the roof ridge to minimize future cleaning needs. These metals are naturally toxic to algae and moss, and when rainwater washes over the strips, it carries traces of the metals down the roof, inhibiting the growth of algae and moss. This reduces the need for frequent cleaning. Algae and moss can cause damage to the slate roof. They can lift and dislodge individual slates as they grow, compromising the roof’s integrity. Additionally, their presence can trap moisture, leading to rot and decay of the underlying structures. Cleaning helps remove these growths and prevents potential damage.

Remember, if you are uncomfortable or unsure about cleaning and maintaining your slate roof, it’s best to consult a professional roofing contractor with experience working with slate roofs. They can provide expert guidance and ensure the job is done safely and effectively. At Steven’s Roofing, we have been working with slate roofing for generations in the Norfolk, VA area. We are happy to help with any questions regarding cleaning, repairing, or installing your slate roof. Contact us today to set up an appointment!


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