Moss acts like a dense sponge on your roof, absorbing and retaining vast amounts of rainwater. During the colder winter months, this retained moisture is subjected to the freeze-thaw cycle, expanding as it freezes and causing tiles to crack, lift, or suffer severe displacement. This process creates direct pathways for water ingress, leading to dampness in your loft space.Furthermore, heavy, wet moss adds significant dead load to your roof trusses, putting unnecessary strain on the structural timber. As clumps inevitably detach, they cause complete gutter failure, blocking downpipes and causing rainwater to cascade down your brickwork. Taking action now prevents costly structural repairs down the line.