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.
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.
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.
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.
I have been asked recently about some of the posts and comments I have been making on things like Facebook and Twitter regarding why you should never pressure wash your roof.
A power washing company recently sent me an e-mail asking for reasons why I think this. So here you go...
The three most commonly used roofing materials in Ireland are probably concrete tiles, fibre cement (man-made) slates and natural slates. I can give you a few examples for each as to why they shouldn't be pressure washed, and anyone experienced in fitting these products will tell you the same.
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.
I was sat in my car outside a local super market a few months back and a guy was sticking leaflets under the wiper blades of other parked cars. After he noticed I was in my car he knocked on my window to hand me his leaflet, he was advertising his 'pressure washing service' that included roof cleaning. I asked him how much to have the roof cleaned?
"It depends on the house boss, give me your number and i'll have a look" he says to me.
"But will that not damage the roof?
While looking through some old photos (late 80s to 90s), it caught my eye that in the background many of the roofs that were visible were all virtually spotless. You can drive to any housing estate more than a couple of years old, or to any house on its own in the countryside nowadays and you'll do well to find one that is not either green with moss and algae or covered in yellow lichens.
So why all of a sudden, in the space of a few years is there so much moss, algae, lichens and other growths present on not only roofs but other external surfaces like walls and paths?