Roof cleaning is the process of removing

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

, mold, mildew, lichen and

moss Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...

from

roof A roof ( : roofs or rooves) is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of temper ...

s. Also cleaning oxidation on metal roofs. Cleaning can extend the duration of a roof's ability to function. Algae and other types of build-up often form on the north and west parts of roofs that are shaded or receive less sun, and can reduce a roof's life expectancy. The presence of soot, dirt, or biomass can affect how much sunlight is absorbed by a roof and thus the amount of heat a building absorbs. Cleaning may be accomplished with a

bleach Bleach is the generic name for any chemical product that is used industrially or domestically to remove color (whitening) from a fabric or fiber or to clean or to remove stains in a process called bleaching. It often refers specifically, to ...

sodium percarbonate Sodium percarbonate is a chemical substance with formula . It is an adduct of sodium carbonate ("soda ash" or "washing soda") and hydrogen peroxide (that is, a perhydrate) whose formula is more properly written as 2 · 3 . I ...

solution, various cleaning products or commercial cleaning services. The Asphalt Roofing Manufacturers Association (ARMA) recommends using a 50/50 solution of household strength sodium hypochlorite (pool chlorine) and water to remove moss and algae. The addition of

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

strips near the roof's peak may reduce the regrowth of algae and moss. Zinc sulfate can also be applied on an annual basis.

Cleaning apparatus

One safe and effective means to clean a roof is an electric agricultural sprayer system, as originally developed in Florida, USA in the early 1990s. The equipment is used to apply a cleaning solution (typically containing bleach) that kills the algae, bacteria, mold, mildew, moss, fungus and other organic organisms growing on the roof. This process is referred to as soft washing. The equipment does not use pressure or mechanical means to clean the roof. Using a pressure washer, or any other gas powered device, to clean a roof at more than 100 PSI can damage the roof. The U.S. based Asphalt Roofing Manufactureres' Association specifies the use of a bleach cleaning solution, without the use of a pressure washer, to remove algae from a roof. ARMA discourages the use of a pressure washer, a flat-surface cleaner or any other mechanical device to clean a roof. Safe, effective soft washing cannot be achieved with a pressure washer, as the Venturi device (downstreaming) cannot achieve sufficient strength solution to kill the organisms, cleaning the roof. Use of different tips on the pressure washer, so that it drops the pressure down to around or less, relies on the pressure of the equipment, and not the chemicals, to clean the roof. Never use a pressure washer as this may damage the roof. Roof cleaning devices exist that may minimize the spread of airborne radioactive materials (in contaminated areas) and other harmful materials, such as

asbestos Asbestos () is a naturally occurring fibrous silicate mineral. There are six types, all of which are composed of long and thin fibrous crystals, each fibre being composed of many microscopic "fibrils" that can be released into the atmosphere b ...

.Airborne Radioactive Contamination in Inhabited Areas - Kasper G. Andersson - Google Books, pp 223 - 229.
/ref> Specialized robots have been designed to facilitate cleaning roofs.

References

{{Reflist Roofs Home improvement Building and grounds cleaning and maintenance occupations

Cleaning apparatus

See also

References