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Winning the Battle With Motorhome Rooftop Mold and Mildew

Originally Published in MotorHome Magazine

Many high-end coach manufacturers use one-piece fiberglass roofs, which are a major upgrade
over lower-cost rubber roofs. One of the advantages of glass roofs is a long,
maintenance-free life, but they still require some cleaning to keep them looking their

Many owners assume that because the roof is fiberglass it will be immune to mold or
mildew, but that’s only partially true. While the dense fiberglass itself will not support
mold growth, the roof will eventually get dirty and that dirty layer consists of bio-matter
such as dirt and pollen that will eventually create a surface thick enough to allow
unsightly mold and mildew to grow on it.

The good news is that fiberglass is very easy to
clean because of its durable nature, and this allows you to utilize a wide variety of
cleaners to make your fiberglass roof look new. There are a few cautions about working on
the wet roof of a motorhome that you should be aware of before you begin.

The first one is
safety. While cleaning the roof you are going to be working on a wet and soapy surface that
is not only smooth and difficult to walk on, but also 12.5 feet off the ground. If you
aren’t comfortable working in this environment, you should leave this job to the local
detail shop (most  Camping
Service Centers offer motorhome detailing). It’s also a good idea to
have a second person on the ground in the event there is an accident, or to help toss up
your cleaning supplies when needed. The next area of concern is the paint on the motorhome.
As you clean the roof, all those chemicals and mold will run down the side of your coach.
Because you and your water source will be on the roof, it’s difficult to ensure that the
dirty water won’t dry on the paint. It helps to have a second person on the ground with a
separate water hose to help rinse the sides of the rig. Depending on the amount of direct
sunlight and the temperature, this may not be required.

Working in the shade in moderate
temperatures (less than 80 degrees), we did not encounter a problem with dirty rinse water
on the paint. However, if you are working in direct sunlight and it is 90 degrees or
hotter, you need to be very careful and maintain a good flow of water while rinsing or else
paint damage could occur. Many of the chemicals used are caustic and if they are allowed to
dry on the paint they may cause permanent streaks. A good flow of rinse water will ensure
that the dirt and chemicals are completely removed.

In order to clean the roof of a
full-size coach, expect to spend 1.5 to 2.5 hours, depending on the initial condition and
your stamina. You’ll need about two 32-ounce bottles of pre-mixed cleaner or 1 quart of
concentrated cleaner. In order to tackle our long-overdue roof cleaning project, we used
Simple Green, Thetford Premium RV Black Streak and Bug
and Camco Full Timer’s Choice Black Streak Remover.
Since the roof is fiberglass just like a typical shower stall, there are other brands and
types of cleaners that will also work well. Just remember most of them are not made to be
used on painted vehicles so be careful if you use these types of products. We found all
products tested did an equal job of cleaning.

You will need a short, stiff bristle brush as
well as one mounted to an extension pole for easier cleaning on large areas. Another
product that we found extremely helpful is Mr. Clean Magic Eraser. We suggest you buy a box
or two for those really tough stains. You’ll also need a water hose long enough to reach
around the entire motorhome as well as a ladder or other way of accessing the roof.

STEP 1: First, walk around the entire motorhome and wet it down with
water. This will help prevent soap and other contaminants from sticking to the paint when
rinsed off the roof.

STEP 2: Next, gather up your cleaning supplies and
safely make your way onto the roof. If your roof is covered with leaves or other debris,
remove them before you begin.

STEP 3: Thoroughly wet the fiberglass roof
using a hose end nozzle and spray a small area with the cleaner of your choice. Using the
long-handle scrub brush, begin working the brush and soapy water on the surface. Depending
on the condition of the roof it could take one, two or even three attempts to fully remove
the grime. Then rinse fully, ensuring that there is sufficient water to carry the dirt and
grime off the rooftop and down the side of the coach.

STEP 4: If you
encounter areas that are very difficult to clean you may have to resort to using the
short-handle brush or a Mr. Clean Magic Eraser. When using the Mr. Clean product we noted
that even the most stubborn stains disappeared by using only light pressure. Be patient and
work on small areas at a time for best results. We found that keeping the sections to
3-foot or 4-foot squares worked best.

STEP 5: Another area that can be
difficult to clean is the sealant used around roof openings such as skylights and roof
vents. Avoid using a brush on this semisoft sealant and instead use the Mr. Clean Magic
Eraser. One or two passes with one and the sealant will look bright and white just like
new. Plus the Eraser foam pads prevent any chance of damaging the sealant.

6: While you’re on the roof, clean the exposed sections of the slide covers if
your coach is so equipped. If you suspect that the entire slide cover is dirty you can plan
ahead by opening them up (extend slide) before you begin the project and do a thorough
cleaning. Again, we found Mr. Clean Magic Erasers worked best on this soft material.

STEP 7: After you finish cleaning one large section, it’s easy to see how
much better it looks than before. The cleaner and generous use of the scrub brush simply
dissolve the grime, which easily rinses off.

STEP 8: Continue the process
one section at a time over and over until completed. We found it best to start cleaning at
the front of the coach at the opposite end that you use for climbing on and off the roof.
This prevents you from walking on the clean surface as you make progress.

9: This is also a good time to clean the various covers and skylights on the roof.
They are likely dirty and in need of a good cleaning as well. Since they are made from
materials that differ from the roof we suggest a soft sponge and the same cleaner you use
on the roof or you can use Mr. Clean Magic Erasers.

STEP 10: After you’ve
cleaned the entire roof, stand back and enjoy the view. It should be sparkling clean and
look nearly new. The final step of the process is to walk around the motorhome and rinse it
off one more time to make sure that there isn’t any residue on the paint. While you’re at
it, why not take the time now and do a full soap and water wash of the coach; that way the
whole motorhome will be clean from top to bottom. As you can see, cleaning your motorhome’s
fiberglass roof is a relatively fast and easy process that can be repeated year after year,
as needed, without any damage to the roof or the need for any additional maintenance.

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