Moss can be a problem if very thick, but is not usually detrimental, and many species of moss are actually protective. , remains the most widely used reference book on the techniques used for thatching.. The thickness of a layer of thatch decreases over time as the surface gradually turns to compost and is blown off the roof by wind and rain. Thatched roofs generally need replacement when the horizontal wooden 'sways' and hair-pin 'spars', also known as 'gads' (twisted hazel staples) that fix each course become visible near the surface. It is not total depth of the thatch within a new layer applied to a new roof that determines its longevity, but rather how much thatch covers the fixings of each overlapping course. “A roof is as good as the amount of correctly laid thatch covering the fixings.”.
Moss can be a problem if very thick, but is not usually detrimental, and many species of moss are actually protective. , remains the most widely used reference book on the techniques used for thatching. The thickness of a layer of thatch decreases over time as the surface gradually turns to compost and is blown off the roof by wind and rain. Thatched roofs generally need replacement when the horizontal wooden 'sways' and hair-pin 'spars', also known as 'gads' (twisted hazel staples) that fix each course become visible near the surface. It is not total depth of the thatch within a new layer applied to a new roof that determines its longevity, but rather how much thatch covers the fixings of each overlapping course. “A roof is as good as the amount of correctly laid thatch covering the fixings.”.