Slate is porous and will hold some moisture. This moisture usually goes away with some sunshine and a bit of a breeze, but in some cases - especially on the shady side of the roof - it can build up and allow algae, moss and lichen to grow right on the stone. Tree sap can also build up on any part of the roof. Slate will naturally fade over time and for many people this is part of its appeal, but stains and organic growth can make your roof look terrible and ruin the appeal of your entire facade. Organic materials growing on your roof can also damage the roof by weakening tiles or causing them to raise up.
Cleaning the Roof
Slate is a very strong and durable material when used on a roof but it is quite fragile when it comes to supporting foot traffic. Slate roofs are also often quite steep and very slippery when wet, so the rule is: Don't Walk on a Slate Roof. Unless you're a pretty handy do it your self person, this is a job best left to pros like CD Kaller, with the know-how, experience, and equipment to clean and repair your roof correctly.
- Use water or a mild cleaner. Stronger cleaners can harm the slate, the hardware, your gutters and your landscaping.
- Always spray from above to prevent a spray from lifting the slates. This can crack the slates and allow water under the slate.
- Use a low pressure spray. Higher pressures from a pressure washer can crack or damage the tiles
- Use a soft brush to remove stains and tree sap. A rake or broom can help with removing moss and other growth
The National Park Service recommends that slate roofing should be inspected every 5-7 years and this may also be a good time to do a good cleaning.
CD Kaller has a real appreciation for older and historic buildings and our slaters are specialists in preserving that character on your slate roof whether its a small repair or a complete roof replacement or new installation. We can help with annual inspections and our highly skilled slaters can clean and repair your slate roof so it retains its character and continues to protect your home for a very long time