This is another one of those questions we’ve heard hundreds of times in our nearly 40 years in the roof-replacement business. The answer to this is “maybe” because we can’t determine whether this is the best course of action without knowing precisely why a homeowner is hoping to clean his or her roof in the first place. A good roof cleaning might just what the (roof) doctor ordered in certain cases, making your roof appear a bit newer and giving your home a little boost in curb appeal.

But in other cases, cleaning your roof is not going to resolve your roofing problems, and in those situations, only an NJ roofing contractor will be able to help. To help you sort out which is which, we’ll explain when you should—and shouldn’t—clean your roof with bleach and water. What’s more, we’ll tell you exactly how to do it (if roof cleaning is the answer).black streaks on roof

When to Clean with Bleach and Water

First thing’s first. When can you clean your roof with bleach and water? The bleach-and-water trick will work best when you’re dealing with algae, which is the more innocuous, if unsightly, form of roof growth. You’ll know you have an algae problem if your roof appears dark and discolored in some areas. You may suspect black mold, but what you’re really seeing are colonies of blue-green algae. Algae can be removed fairly easily with bleach and water.

Your roof can also be cleaned with bleach and water if you have a moss problem, but only if the moss growth is very new and hasn’t spread over large areas of your roof. This type of roof-moss problem can possibly be removed with bleach and water if you recognize it early enough. (Many people, unfortunately, mistake early moss growth for lichen or algae.) However, if you’re seeing thick, clumpy patches of green growth, you’ve got a serious moss problem, and it’s this form of roof growth you need to worry about.

Why Roof Moss is Worse than Algae

Many people are surprised to learn that moss is the more insidious form of roof growth. Frequently, we hear from people who think moss is harmless and even adds a bit of a quaint, Old-World charm. It’s algae that folks are frequently more concerned about, with the black, ugly streaks it paints on roofs.

But moss poses a bigger problem mainly because of its physical characteristics. As you might suspect by its spongy appearance, moss has the ability to soak up huge amounts of rainwater. However, since you can’t climb up on your roof to squeeze that water back out again after each soaking, it just sits there. Eventually, it leaches through your roofing, soaks the underlayment and begins to penetrate the wood sheathing below. From there, your roof’s decking starts to rot, develop mold, weaken, and warp. At this point, your roof is in serious trouble.

How to Clean Your Roof with Bleach and Water

Let’s assume first though, that you have either an algae problem or a very early moss problem. In this case, you can clean your roof with bleach and water as long as you do so safely, properly, and infrequently.

Please note, this cleaning method is for asphalt shingles only and is only advisable IF you have easy access to your roof. We do NOT recommend climbing onto roofs and we do NOT recommend doing this work solo – always use the buddy-system and have someone close at hand to help support your ladder.

We can’t stress enough – If you don’t have asphalt shingles and you don’t have easy access to your roof, call a roof-cleaning company!

To clean your roof, first wet foundation plantings down, which protects them from the bleach mixture. You’ll want to use a regular garden hose, not a pressure washer, for this entire procedure. Use a sprayer that you can attach to your hose, which you’ll fill with equal parts chlorine bleach and water. After spraying the roof with the mixture, allow it to sit on the surface for 15 to 20 minutes before rinsing thoroughly with clean water.

A few tips for doing the job well: First, don’t clean your roof on a sunny day, since the solution can evaporate too quickly. Instead, choose a cloudy day when there is no threat of rain. Also, have patience and let the solution do its work. The algae will wash away during subsequent rainstorms, and moss will eventually loosen to the point where it can be removed with a leaf blower. Finally, washing your roof too often will cause the granules too loosen, shortening the life expectancy of your roof, so if you find the algae or moss keeps coming back, consult a roof-cleaning professional.

What to Do When Moss Growth Has Taken Over

If you’ve got a moss problem that’s thick and clumpy or covers large patches of your roof, it’s very possible your roof is already damaged beyond repair. In this case, walking on your roof would be extremely dangerous due to the rotted decking, so please don’t attempt to clean it. Instead, contact George J. Keller and Sons to discuss roof replacement, which is generally the best and safest option. We’ve installed almost 10,000 roofs during our nearly four decades in business, so had plenty of experiencing replacing even the most waterlogged, mold-infested roofing systems. Give us a call today at 973-927-0963 and we’ll be happy to advise you on the best course forward.