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Trim overhanging tree limbs. Remove leaves and other debris. Replace damaged or rotten shingles. Apply a 5% oxalic acid solution on your roof. Clean your roof regularly.
One of the most important ways to maintain your roof is to remove any tree branches or limbs that overhang your roof. Not only will these limbs contribute to the accumulation of debris on your roof, but the shade they help create will encourage the growth of mold and lichen.  You may be able to cut smaller limbs or branches by yourself. If you have large limbs that overhang your roof, you may need to call in a tree cutting service. You should periodically remove leaves, sticks, and other debris from your roof. Accumulated debris will increase the amount of moisture on your roof and encourage the growth of mold and lichen. If you have a long broom or pole, you may be able to remove a lot of debris from the ground or from a ladder. Use a hammer to remove any nails or tacks that secure shingles to your roof or other shingles. Remove the damaged shingle. Then, tack and nail down a replacement shingle. If you’re not comfortable replacing a shingle yourself, you should contact a licensed roofer or contractor to do it for you. This solution will help neutralize the blue-black stain that occurs on shingles overtime. In the end, you’ll have shingles that appear brighter.  Be very careful using oxalic acid, as it is a toxic substance. Oxalic acid won’t keep shingles bright. If you don’t remove the source of the stain (usually iron from certain nails), you’ll have to apply it again. How often you clean your cedar shingle roof depends on the climate you live in. To determine this, you need to consider the challenges the environment you live in pose to your roof.  Cedar shingles in wet and overcast climates should be cleaned yearly. Cedar shingles in sunny and dry climates may only need to be cleaned every 2 to 3 years.