Choosing A Roof Cleaning Contractor
You've decided that stepping on your roof wet to wash off those black spots isn't suitable for you. This is probably a wise choice. Cleaning your roof yourself can be extremely dangerous. You might have thought about using what you refer to as the "spray and sit" product that you spray on your roof from below.
However, you may have realized that, after purchasing or renting the entire equipment required and waiting for a few weeks to see rain wash dead organisms out, you'd likely need to go through the entire process and be cost a couple of times before you see results. You've chosen to employ an expert roof cleaning service.
The hard part of hiring a contractor is: who do you choose? It's not as easy as picking a phone number out in the telephone book or searching for roof cleaning services. This is only the beginning. You must be aware that there are important distinctions between roof cleaning contractors.
The black staining on your roof is caused by cyanobacteria Gloeocapsa Magma. It is what most roof cleaners call algae. It is a single-cell organism, and the stain is made of millions of cells, alive and dead.
If the entire layer isn't eliminated from your roof, the stain will return in no time. Bleach is a powerful oxidizer and when it is applied to algal glue it causes it to oxidize the upper layer of the stain. The stain disappears. But underneath this oxide layer, the glue that is left behind remains.