So you might say "Why would I want to clean my roof? That's the way a roof is supposed to look...right?. Why "waste" the money?" Well, there a couple of reasons why it is important to clean a slate roof. The first reason is that it simply looks fresh and bright but the most important reason is Winter Weather in New England. Almost without exception, slate problems occur where snow, moss or algae has lain on the slate surface for prolonged periods. In cases where trees are not hanging over a roof, the surface is problem free (trees create a fertile environment beneath them that fosters moss, algae and lichen growth which holds moisture and snow in place). In winter as the daytime sun melts some of the snow, the water falls into the slate through fissures and cracks and absorbs into the slate. At night it freezes and expands, widening the cracks and pores, providing larger cavities for the next days melting water. The cycle continues with tremendous expansion and contraction of the slate around the cracks. A once strong and solid surface has become broken and flakey. This situation will requires expensive repair or replacement. The best way to eliminate or reduce this problem is to eliminate the algae, moss and fungus.
Important Note : Proper surface cleaning involves either physical scrubbing or some level of pressure to remove the plaque and fertile substrate. There are several enterprises out there marketing products that they claim do not require rinsing. "Spray and Forget" and other "No Rinse Roof Treatments" are good starts but do not remove the foundation which will only invite regrowth in a very short time, sometimes in only a few months. We all know that mouthwash alone doesn't make for healthy oral hygiene, and that brushing and flossing are necessary. It's no different with roofs, siding, decks, or any other surface. There is lots of documentation on this. Common sense also works.
illustrated here, lichen
completely digest the silica grit,
bare asphalt. This will not
visible on a
darker surface. It is important
granules remain on an
roof so that they can
do the job
of reflecting the sun's rays.
proper cleansers and a low
rinse will ensure that your
granules remain intact.
was enough lichen and moss
on this 25 year old roof in Northern New Jersey to
support a habitat
for tree frogs. Once cleaned, this roof looks nearly new
all these years. This is mostly due to two factors. One;
of strong sun at the location of this
two; these shingles were handsplit
tapered shakes. Nothing really can compare to these.
They will absorb
a lot of abuse. Nonetheless, there were some rotting
If we all
airborne sea salt would cure and
preserve the cedar shingles for
us, which would prevent
If you want
stand up to our New England
environment, then it's time to
consider a maintenance plan.
gentle on roofs
and not at all harmful to plants,
pets or people.