How Do You Maintain Fiberglass RV Siding

How Do You Maintain Fiberglass RV Siding?

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Last Updated on April 13, 2023 by Jessica Lauren Vine

Are you asking, “How do you maintain fiberglass RV siding?”

Fiberglass siding is the most popular siding option available on RVs today. When maintained properly, fiberglass siding lasts as long as the aluminum siding found on less expensive RVs while providing a sleeker, more upscale look. 

When it’s new, fiberglass RV siding is a uniform color, smooth and shiny but that appearance will not last forever.  Over time, dark streaks will appear and the finish will eventually turn to a lighter, duller, or even chalky rendition of its former self.  To prevent that, it’s best to do routine maintenance to keep your fiberglass shiny and looking great.  Here we’ll look at how to do that basic maintenance as well as how to address more serious issues if you’ve let the maintenance slide a little longer than you should have.

For our fiberglass-sided travel trailer we do the following maintenance routine for the siding.


We periodically go over the RV looking for issues related to the siding. These issues cover both the general appearance of the siding, but also things like seams between joints or even interior issues like making sure there are no plumbing leaks. While these issues may sound unrelated to the care and maintenance of your fiberglass siding it is important to remember two things.

First, your fiberglass siding probably isn’t just fiberglass. Most exterior fiberglass siding materials are actually laminates of an exterior layer of fiberglass and a thin inside layer(s) of a wood material like Luan. This allows the fiberglass layer to be very thin (and less expensive) while still having the rigidity needed to form a wall.

The second thing to remember is that water leaks can cause damage far from the leak source.  Water has an amazing ability to move to the lowest point in your RV and in most cases that will mean finding its way to and down an exterior wall.  If water permeates the luan backing of the fiberglass laminate then delamination will occur.

This will look like unusual waves or bubbles in your otherwise smooth and perfect fiberglass sides. If you see signs of this happening to your RV, look for and address the source of your water issue immediately. Once the structural integrity of the fiberglass laminate has been compromised it may be difficult to eliminate the source leak.  If you suspect this to be the case you may need to have someone who specializes in RV fiberglass repair have a look at it.

Assuming we don’t find any issues which can cause damage we move on to the overall appearance and make note of issues like dirt, black streaks, and oxidation.  From there, we’ll tackle each issue in order.

Wash the RV

Step two in maintaining your siding is washing it regularly. Washing does three important things for your RV. First, it forces you to get up close and personal with the entire rig. If you missed anything in your step 1 inspection, you’ll likely catch it now. RVs are relatively huge and we tend to look at them from a distance where we can miss a lot of the little things.

This is actually a great argument for always washing your RV yourself.  Nothing against RV cleaning services, most do a great job but doing it yourself forces you to notice things that you may otherwise miss. Next, washing your RV obviously removes the dirt, or at least that’s the goal.

Having a clean RV looks better but also helps prevent fine damage to your fiberglass’s surface.  Brushing against your dirty RV as you walk by is like brushing against it with super fine sandpaper. Those tiny scratches then make it harder to remove black streaks and wax later on.

Finally, when you’re done washing the RV, it is clean and ready for the next steps of the maintenance process.  You should never skip washing before moving on to the next steps since they require physical rubbing of the fiberglass surface.  Doing these steps on a dirty RV will damage the surface.

The best way to wash an RV is with lots of water and a quality RV or fiberglass boat cleaner. These products are designed to gently clean fiberglass surfaces. Work in sections, hose down the section you are working on from top to bottom. This will remove any large debris from the surface and wash it to the ground.

Then, using an extension brush loaded with your cleaner of choice, gently brush the surface.  Again, you want to work from the top down. Once you’ve completed an area with the brush, rinse it down with the hose again from top to bottom, and then move on to the next section. Repeat this until the entire RV is done. Once it is done and dried, look everything over again to determine what needs to be done next.

If you do this routinely it will likely look great and be ready for wax, in which case you can proceed to that step.  If there are other issues, we’ll address those now that we have a clean surface to work with.

Remove Black/Dark Streaks

Black or dark streaks are a common issue on fiberglass RVs.  These are generally caused by organics getting into the fine scratches in the surface of the fiberglass.  This is why they usually appear where water collects like off the bottoms of windows, under hatch latches, or down the sides under your gutter spouts.

Newer RVs are less prone to them since their surfaces are smoother and they haven’t had a chance to collect the organic materials that cause them.  Unfortunately, once they appear, removing them can be a tedious process.  You’ll need to use a black streak removal product like Bio-Kleen M00505 Black Streak Remover

While you should always read and follow the specific instructions for the product you choose, these are usually as simple as spray on and wipe off. Tougher stains may require reapplication or mild scrubbing with a soft microfiber cloth to completely remove them.  You should never use any abrasives to remove black streaks or stains.

Remove Oxidation/Haze

Oxidation is also a common issue on fiberglass RV sides. Oxidation occurs when the UV rays of the sun react with the outermost surface of the gel coat on your fiberglass. This causes the outermost layer to break down and turn a chalky white. This process means you’re most likely to see it on surfaces that face the sun and/or which have not been protected with a quality UV protectant wax.

How to address the issue will depend on how bad it is.

Minimal oxidation is usually removed simply by applying a quality RV wax. All gel coats oxidize and even if the surface looks perfectly glossy there is likely some oxidation there.  The mechanics of wiping wax on, letting it dry, wiping the dried wax off, and polishing it by hand is usually enough to remove very light oxidation.

If you wash and wax your RV frequently, you may never experience heavier oxidation issues.  Also, if your RV is painted you may have fewer oxidation problems.  Paint can still oxidize, but it takes longer and is less noticeable than an oxidized gel coat. 

RVs with painted fiberglass are far less common, if you have one then the paint can be freshened up using standard paint polishing techniques.  However, we won’t get into those here.

Once the fiberglass starts to look hazy you probably have an oxidation issue that a simple waxing won’t correct easily.  In that case, you’ll need to go to something with a little more grit.  Lighter oxidation issues can be handled with a simple RV polish while heavier oxidation will need a product designed specifically for oxidation removal.  If you go with the latter, you’ll also need the polish to bring the shine back after you’ve used the oxidation removal product.  In many cases, you’ll want to just buy an entire kit that will have all the products you need to maintain your fiberglass exterior.  These kits are great because the products are designed to work together which can save you a lot of time and effort.   They also tend to be less expensive than buying each component separately.

The best way to tackle oxidation removal is with a polisher.  You’ll want one with variable speeds so you can control how much heat you’re making as you polish.  Dual action or random orbit features are good too, but not completely necessary. In addition to the polisher, you’ll need polishing pads, one for each type of product you are using.  You’ll need a coarser one for the oxidation remover and a fine polishing pad for the polish. You can also use a separate polishing pad for waxing. When using this type of polisher, it is important that you don’t let it sit in one spot.  Always keep it moving and don’t let the pad/surface dry out.  Work slowly in small sections and check your progress frequently. These things work fast and until you get a good feel for them, you’ll want to take your time to prevent damaging the surface.


The final step when you have a clean, shiny, oxidation-free surface is to apply wax.  Always use a good quality RV wax intended for fiberglass sides. These waxes usually contain Carnauba wax. Carnauba oil is known for its excellent UV protection abilities so it will do a great job protecting your RV from oxidation.  Wax does not need to be applied or removed with any fancy tools.  A simple microfiber cloth and some elbow grease are all you’ll need. Make sure you use different cloths to apply and remove the wax and avoid working in the direct sun. 

Once your wax is removed, then you’re good until the next cleaning.

Other products, home remedies, and urban legends. 

You may be inclined to search the internet for shortcuts, DIY product recipes, and hacks to make this process easier, cheaper, or last longer.

I’m all for finding the best solutions which cost the least and last the longest, but you should approach these solutions with extreme caution.  The front cap on our travel trailer oxidizes quickly and is a lot of work to maintain.

Searching the internet for a more permanent solution, I came across several recommendations to use commercial floor tile wax. Several people raved about it, billing it as a near-perfect permanent solution. Further research revealed it is indeed somewhat permanent, even if you don’t want it to be.

As it turns out, it will eventually yellow heavily and begin to crack and flake off

What doesn’t crack and flake off is next to impossible to remove.  What seemed like a great solution would likely result in a worse situation within a year or two. Fortunately, I did a lot of research ahead of time, so I never got to the point of actually trying it. The point is that your fiberglass-sided RV is an expensive thing.

Don’t take shortcuts.  Use quality products designed for the task and put the work in.  You’ll be rewarded with a rig you can be proud of that will last and hold its resale value for years to come.

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