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|Posted on 13 May, 2013 at 13:00||comments (6)|
Keeping a roof clean
By F. Moal
When looking at an ageing building, few people cast a critical eye at the state of the roof. The windows are clean, the garden tidy and the interior spotless, but the roof is almost invariably unkempt. Black moulds hide it's colour and moss slowly mats itself in the bonds, so slowly that few take notice.
The encroachment of grime and moss has it's effects : Beyond the architectural downgrade the fabric of the building is at risk. Doing nothing is ultimately the expensive option. The risk varies with the nature of the roofing material : Thatch and wood shingles are at a more immediate risk of decay.
Metals erode under the acidic releases of lichen and moss. Lead and zinc used in soakers and rainwater disposal will thin down to eventually leak. Clay tiles need to dry between rainfalls to fulfill the promise of durability - if not premature shaling or frost damage may occur.
On all material the permanent presence of a bio film is deleterious by increasing capillary creep in laps and interstices. This in turn leads to undetectable moisture ingress. Generally materials retaining moistures are prone to contamination and combined with a shady winter exposure porous materials such as concrete tiles will become a good host for moulds such as A. Niger, then algae, followed by moss and lichen. As the bio film becomes established, the moistures are more permanent, and the cycle accelerates.
Architects do not seem to enter this constrain in their choice of roof material :
This was of no consequence in the days of acidic rain, but cleaner air results in nature reclaiming it's place in unforeseen ways. There is no easy answer to the return of nature :
Excessive moss has to be removed by hand. Mechanical means used on the ground are ill adapted to a pitch roof.
Jetting causes irremediable erosion to the surface. As a result the un-wanted host returns with a vengeance, only to hide the uneven, permanent discolorations of the roofing tiles. After clearing the roof from the bulky growth the next and final step is to spray the area with a dedicated anti algal wash. The right product, such as Mossgo-Pro will kill the remaining biological life at the surface and, most importantly, in laps and interstices. The dead bio film will soon loosen under diurnal cycles, helped by the wind, rain, heat and frost.
Self cleansing is a lengthy affair - months in most cases with latent effects stretching over a period of two or three years. The roof will become cleaner with the change of seasons and reveal it's original colour and texture.
There is no known preventative measure of any durability.
Clear hydrophobic resins degrade under UV in a matter of months. The same causes - substrate porosity and sun exposure - will have the same effects, at the same rate. This however is slow and a roof treatment is to be regarded as decennial maintenance.
Further maintenance will not be as heavy as the first clean, if carried out as or before the surface contamination triggers the condition for accelerated growth.
On the continent, antiseptic roof shampoo has been standard practice for decades. Roofing firms offer it as a standard way of finishing remedial work and as preparation to fitting out solar panels. In Britain the practice is expending quickly : The process has been adapted to the northern more demanding climate of the British Isles.
The website www.roofclean.co.uk hosts a wealth of information on roof maintenance treatment.
HD Roofing Services in Ireland, are among the most experienced contractors to use the Mossgo pro roof cleaning system. For more info or advice call Andrew on 087 9323863 or mail him at [email protected]
|Posted on 15 April, 2013 at 13:28||comments (1)|
Just a quick one on something that we are coming across a fair bit lately.
Walls, roughcast renders and pebble dash treatment.
The extensive use of rough cast renders and pebble dash on walls has led to the development of appropriate cleaning techniques.
Coloured renders or Monochouche as it’s also known was particularly popular during the most recent building boom here in Ireland.
Although the new build industry has all but gone these types of plastering are appearing more and more as services such as External Insulation continue to grow.
There’s nothing wrong with these wall coverings, done right they actually look really well and versus a traditionally plastered then painted wall I’d choose a coloured render all day long.
Like all external surfaces though it’s only a matter of time before they become dull, discoloured and stained from growths such as red and green algae or lichen. Trouble is, due to the granular type finish to render or the easily loosened pebbles on pebble dashing the very last thing you would want near these surfaces is PRESSURE WASHERS!
I recently done a roof repair for a girl whose house was finished in a bright yellow render, the place was immaculate, you could tell she spent many hours in the garden and cleaning her home. A little too much as it happened. I asked what happened to the gable wall where I noticed a section where there was streaks going in all sorts of directions. Putting her hand to her forehead she told me that after noticing a red colour appearing on the wall she decided to try and rinse it off with her little electric pressure washer, big mistake!
Like our Roof Cleaning technique, our treatment of Moss, Algae and Lichen is soft and safe enough to use on any type of external surface without any risk of damage to the substrate, and without the use of PRESSURE WASHERS!
|Posted on 10 January, 2013 at 5:14||comments (0)|
Breaking the Mould
Mould is easier to clean than the soot of old, but with the return of clean air, nature has reclaimed ground in a way not always foreseen. Problems sometimes arise when a building does not receive its full share of sun. In other places there are not enough sunny days in a year to stop deleterious growth. The issue does not affect all materials in the same way. Most roofing materials will someday need cleaning, but not all, and not at the same intervals. Choosing a roofing material with regard to its susceptibility to mould and moss encroachment is good design practice in shady locations. Below is a brief summary of material behaviours towards biological growth and reactivity to a non-aggressive biocide treatment.
Natural slates are not porous and display a smooth surface. As a result the material dries rapidly and is not naturally prone to roof growth with the notable exception of yellow lichen in coastal environments. The material cleanses readily upon treatment. It is a product of choice for shady locations.
Manmade slates offer some of the advantages of natural slates, but not always to the same degree.
Fired clayof good quality is not porous. The surface dries rapidly and sheds the bio film satisfactorily when treated. The roof surface is however more textured than slates offering intersects where growth can take a foothold.
Old clay tile roofs are fragile and are best treated from the eaves.
Concrete tilesare not indicated in the vicinity of tall trees. The high porosity combined with a rough surface provides a natural host surface. Removing mated moss from concrete tiles is labour intensive. The material cleanses well, but more slowly than other materials. The alkalinity of the surface seems to benefit black blanket moulds. In recent years smooth and less absorbent concrete tiles have arrived on the market. They are a better choice for higher humidity regions.
Zincis not a natural host to live contaminants. It is however susceptible to organic acid releases from rotting leaves, moss and lichen and should be avoided on lower draining slopes and box gutters.
Leadis also not a natural substrate for life. It is vulnerable to mild organic acids but paradoxically resistant to harsher mineral ones. Mossy tiled roofs draining into lead gutters will eventually jeopardise its integrity.
Copperhas biocide properties. Water running over copper will acquire some of its cathodic properties by contact and hampering further downstream growth. The protection may not be sufficient to maintain the tiles in pristine condition along the whole rafter length. On canal tiles the protection is limited to the trough, where it is still the most needed.
Aluminiumis not particularly affected by acid releases. Water running over it will become anodic and display the reverse effect to that observed on copper. The illustration of this is seen in the splash area of TV aerials.
Flat roof feltsof bituminous kinds are not unduly prone to moss, but ponding, cluttered designs and raised walkways will host them. PVC felts become very slippery, but as is usual with algae, the treatment is rapid.
Organic materialsare best used in full light where they can dry rapidly. Durable presence of moulds and algae will eventually jeopardise their integrity as roof covering. As the lining of wood shingles washes away, the grey cellulose needles are exposed and offer a slightly abrasive surface hosting algae. The treatment will reinstate the silver grey appearance for some time. Thatch, if badly affected will need combing beforehand.
For the existing stock, periodical maintenance is the solution. The general wisdom is to opt for the milder cleaning processes before considering harsher ones. Blanket moss has to be removed by hand, bagged and disposed of in all cases. The tiles can then be treated by the appropriate biocide. After the treatment, the dead bio-film will begin to loosen under diurnal and seasonal cycles, until the roof has regained the true original colour of its material. The rate of cleansing will vary greatly with the type of material, and the exposure to wind and driving rain. Not all chemicals are appropriate, and a few only authorised by the Health and Safety Executive (HSE). All formaldehydes, caustic soda or bleach based chemical are proscribed.
The application method and knowledge is as important as the biocide itself. Jet cleaning is seldom appropriate to roof cleaning. The pressure removes surface aggregates, creating a moisture retaining surface favourable to the return of the contaminants. Tile impregnation and coatings are ways of mitigating the damage done by jetting, but at a cost sometimes higher than simply replacing the tiles by new ones. In conclusion, the return of clean air means new parameters for the choice of roofing materials by the Architectural Technology professional, and the specification of a nonaggressive maintenance procedure for existing roofs. This is easily searched for on the Internet. A comprehensive approach to roof cleaning and the provision of specification support is a sign of an experienced specifier.
The author is Managing Director of TVSPLtd, which specialises in a roof cleaning process known as the Mossgo Roof System, supplier to HD Roofing Services Ireland.
|Posted on 21 June, 2012 at 9:02||comments (7)|
|Posted on 6 June, 2012 at 9:34||comments (0)|
Algae are a diverse group of simple, plant like organisms. Like plants, most algae use the energy of sunlight to make their own food, a process called photosynthesis. However, algae lack the roots, leaves, and other structures typical of true plants. Algae are the most important photosynthesising organisms on Earth. They capture more of the sun’s energy and produce more oxygen (a by-product of photosynthesis) than all plants combined. Algae vary greatly in size and grow in many diverse habitats. Microscopic algae, called phytoplankton, float or swim in lakes and oceans. Although most algae grow in fresh water or seawater, they also grow on soil, trees, and animals, and even under or inside porous rocks, such as sandstone and limestone.
Algae also form mutually beneficial partnerships with other organisms notably with fungi to form lichens-plant-like or branching growths that form on boulders, cliffs, and tree trunks.The algae provide oxygen and complex nutrients to their partner, and in return they receive protection and simple nutrients. This arrangement enables both partners to survive in conditions that they could not endure alone.There are more than 15,000 kinds of lichen in the world. They can grow on any surfaces and anywhere in the world. The lichen is a symbiotic association between a fungus (mycobiont) and an alga (photobiont). The filaments of the fungus support cells of the algae.The fungus needs carbon and energy. Generally it finds it on dead organic material or on living organisms (parasitism) which cause disease to plants. The algae, capable of photosynthesis, provide the carbohydrates it needs. It also provides some vitamins (biotin, thiamine). The algae changes the structure of the fungus which can absorb a lot of water and a part of sunlight to protect the algae from certain strong wavelengths.The fungal component of lichens produces organic acids that disintegrate rock, giving the lichen a better hold and contributing to the weathering process, which eventually turns a rock into soil. Lichens can withstand great extremes of temperature and are found in all parts of the world. In the built environment, the organic acids are notoriously deleterious to zinc and lead used for flashing or gutter lining.
Many small plants bearing the name moss are not mosses in that they do not belong to the Bryophyta family. The “moss” found on the north side of trees is the green alga Pleurococcus;Irish moss is a red alga. Beard lichen (beard moss), Iceland moss, oak moss, and reindeer moss are lichens. Spanish moss is also a term used for a lichen. The term moss used in connection with MossGo does not refer to Bryophytas, but to the vernacular use of the word.
|Posted on 17 May, 2012 at 11:37||comments (0)|
|Posted on 27 April, 2012 at 14:39||comments (1)|