Problems and Maintenance FAQ's

Marley does not recommend foot traffic directly on the roof tiles or covering.  Cracks or micro-cracks can occur on the roof covering if roofs are trafficked without appropriate access equipment. British Standard BS 8000: Part 6: 1990 'Workmanship on building sites' states that any roof or vertical work in slating or tiling should be 'treated as fragile'. The standard recommends that an adequate number of crawling boards and ladders should be used when accessing completed areas of roof, using packing between boards and tiles to avoid damage.

The use of high powered jet washes is not recommended as it can damage the surface of the slate or tile, thus reducing its expected life considerably.

Cracked or broken tiles are an unfortunate and common occurrence, especially on lower level roofs and usually a result of maintenance traffic, such as window cleaners. It is highly recommended that cracked tiles are replaced as soon as convenient, taking care not to damage adjacent tiles during replacement or when accessing the roof. It is important to ensure that anyone accessing your roof utilises suitable crawl boards and cat ladders to spread weight and reduce point-loading which often leads to the damage of tiles.

In common with all construction materials, roof tiles or slates gradually change in appearance over time through the action of natural weathering. these include:

The growth of lichen, algae and moss on the surface. The accumulation of fine dust deposited from the atmosphere. The chemical and mechanical action of rain and run off water. The chemical effects of prolonged exposure to sunlight.

Given the complexity of weathering and the influence of local exposure conditions such as aspect, air purity and average relative humidity, it is not possible to predict with certainty the time period over which such colour change will occur or the outcome at any particular point in time.

Moss and lichen tends to flourish in rural areas or where trees are nearby and where there are shady, damp conditions. Steeper pitched roofs are less likely to support moss and lichen growth as they shed water more quickly than low pitched roofs. By contrast, north facing and shallow roofs tend to remain damper longer and attract the growth of mosses and lichens.

In normal circumstances, the growths are not harmful to the tiles or slates. However, in some extreme cases this growth may affect the drainage of water down the roof. In such cases, they should be removed to avoid possible water ingress into the roof space. There are several methods for the removal of moss and lichen

• Spraying with a toxic wash Copper wire Scraping
• Before proceeding with any remedial work to remove moss or lichen, we would recommend speaking to a professional.

If unsure, you should contact the Marley technical department for further details.