Botanically, mosses are non-vascular plants in the land plant division Bryophyta. They require sufficient moisture, access to nutrients and harvest sunlight to create food by photosynthesis. There are approximately 14,500 species of mosses. The most common species in urban Ireland are the greycushioned grimmia, Grimmia pulvinata; thickpoint grimmia, Schistidium crassipilum; and the wall screwmoss Tortula muralis.
Although mosses do not cause direct damage to roof tiles, they increase water capillary creep causing in the fullness of time corrosion of the fixings and ageing of the overall structure. They can cause some lifting when growing in the vertical bond. As they absorb moisture, they also add weight to roofs and when they become heavy enough or dislodged by bird activity etc, they can fall in gutters and down pipes and cause blockages.
On the ground the deleterious effects of mosses is slower to take effects, except on artificial grass, where they rapidly clog the drainage leading to runaway maintenance issues. It is recommended to clear moss before treatment. This is done by hand on roofs, or mechanical brushing on the ground, particularly on artificial grass. AlgoClear® Pro being de-activated in contact with biomass, it makes good sense to reduce it’s volume before applying the biocide.
