I have a wood shake roof and of course have a ton of moss in certain areas. What is the best chemical to get rid of the moss? A mixture of bleach and water or something else?
While you may be able to remove it temporarily it will grow back. Be aware some of the removal chemicals and methods can damage the shakes below.
Scr-ape off what you can then scrub it down. Not much else after that except repeat the process every few years.
To eliminate the moss, eliminate the shade and the water.
Because moss is a plant(ish) material, it uses photosynthesis to survive. That means it can be killed with a copper sulfate solution, just like pond algae. However, spraying this (or any other chemical) on a rooftop will result in a huge mess down below, as the chemicals drain off and fall to the ground all around the building. This will also destroy shrubbery, grass, potted plants, etc. - any other plants that get exposed to the chemical. Best to use physical methods only unless you can 100% control the overspray and runoff, no matter what chemical you choose.
Try bleach. Use a garden sprayer to apply it.
Where is the house located? Wood shake is banned in my area, due to fire risk.
Start with bleach and water to knock dow the majority. Follow up with a sodium borate solution mixed with ethylene glycol antifreeze. You ca purchase it under the name Timbor or Boracare. Boracare is an out of the bottle solution, but pricy. Timbor has to be mixed with antifreeze and water.
Make your own with 2 parts boric acid (roach powder) and 3 parts Borax laundry aid. 2 pounds of that mix to a gallon of antifreeze heated to 280 degrees F. Needless to say heat it outdoors on a camp stove. Then dilute with one gallon of water and spray with a garden sprayer. Repeat every year.
Bonus, sodium borates increase the fire resistance of the shakes. It is used to treat cellulose insulation.