A roof with moss, lichen and piled-up leaves is not only a question of looks. The technical guide of the Portuguese ceramics association (APICER) and the Ceramics and Glass Technology Centre (CTCV) says roof faults come mostly from a total lack of maintenance, and recommends a yearly routine of inspection and cleaning. This section explains what cleaning a roof means, when it is needed, what it costs according to the sources we found, and what to ask whoever does the work. We do not clean roofs: we give information, with sources.
Updated 2 November 2026.
The essentials
- Cleaning the roof is maintenance. The APICER and CTCV guide asks for inspection and cleaning once a year, and drainage (gutter) maintenance twice a year.
- Moss, weeds and leaves can block the water. The same guide describes vegetation that blocks drainage, moves and breaks tiles and holds water, especially at the eaves and in the gutters.
- Asbestos-cement roof: do not pressure-wash or scrub. Any handling can release fibres. See the asbestos guide.
- Cleaning is not repair. If tiles are broken or displaced, cleaning does not stop a leak.
- Working on a roof is work at height. Falls are the main risk. Do not climb up without protection; hire people who work with their own safety equipment.
When cleaning is needed
Signs that need attention, according to the APICER and CTCV guide: vegetation growing on the roof, gutters and eaves full of soil and leaves, and water that no longer runs off as it should. In all three cases the guide treats the situation as a warning sign that may need a deeper intervention than a simple wash.
Moss and lichen alone, with no broken tiles and no leaks, are mostly a matter of upkeep and looks. DECO Proteste, the consumer association, said in a 2022 article that moss damages ceramic and slate tiles and lets water in more easily.
Where to start: three questions
- What roof do I have? Ceramic or concrete tile, slate, asbestos-cement sheet, sandwich panel? If it is old asbestos-cement, stop here and read the asbestos guide. If you do not know, do not climb up; ask someone who does to look from the ground or from scaffolding.
- Is the problem only on the surface? Moss and dirt are one thing. Broken tiles, rotten battens, loose flashings and holed gutters are another, and need repair. The guide to leaks helps tell them apart.
- Who will work, and with what protection? See the guide on hiring a cleaning firm: documents, VAT, safety and what the quote should say.
The guides in this section
- How a roof is cleaned: methods, risks and when not to
- What it costs to clean a roof: what we found
- Hiring a roof cleaning firm: what to ask, VAT and safety
Other guides that overlap
- Roof checklist before winter
- VAT on roof works: cleaning is outside the 6% rate.
- Warranty on roof works
- Quote checker and check a contractor
What we could not confirm
- Official cleaning prices. There is no state table or trade-association table we could read. The figures we quote come from a private portal and are in the price guide.
- One “right” method or pressure for every roof. The APICER and CTCV guide gives none. The DECO Proteste article is consumer advice, not a standard.
- How many years a protective treatment lasts. We found no independent source. Ask the product maker for the data sheet.
Sources (read on 2 November 2026)
- APICER and CTCV, Guia para Projeto e Aplicação de Telhas Cerâmicas, 2nd edition, 2018 (section 7.4.2, page 95: yearly inspection and cleaning; case 6, page 102: parasitic vegetation). In Portuguese.
- DECO Proteste, Máquinas de limpeza de alta pressão: dicas para trabalhos de manutenção da casa, 3 February 2022. In Portuguese.
- Our guides on asbestos and VAT, with their own sources.