Painting Fiberglass Siding

I read a few old posts, but it doesn't seem that they were resolved.

I am going to be painting my fiberglass siding due to cover exposed fibers and stains from dirty runoff water from the roof. (I will also be changing the upper moulding to gutter moulding to prevent it again.)

I stopped at a paint store and they pointed me to XIM UMA (Urethane Modified Acrylic) primer + sealer to try. It seems that the urethane helps it bond to just about anything, including chalky, dirty, and glossy surfaces; even without prep work. I am still going to wipe my siding down to minimize dirt and oils.Once I prime it, they say I can use any exterior paint that I want. It is spray gun compatible and if I need to thin it, all I need is a splash of water.

I bought a quart to try a test patch before I buy in bulk. It is $20/qt or $60/gallon. I am going to try it on one of my storage doors, first. I will post before and after pics with results. If it works well, I am going to paint the rest of the cab this weekend or next. I haven't decided if I am going to paint the driver section yet. The paint up there is faded, but still intact. The vinyls have worn out though. Luckily, my local RV dealer sells new vinyl for about $40.

https://www.rustoleum.com/product-catalog/consumer-brands/xim/bonders/advanced-technology-uma-white/

The bay doors are a different material than the fiberglass walls, so maybe not a good test.

I'm curious if you have considered other primers, e.g. those specifically for fiberglass. I've painted a fiberglass boat and used the primer recommended for the paint (which was an epoxy).

TAKE IT BACK.
Go to an automotive paint store, explain what your dealing with and get their recomendation.  Painting fiberglas can be a challange.  Doing it right is not cheap or fast. 

Gary RV_Wizard said:

The bay doors are a different material than the fiberglass walls, so maybe not a good test.

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On mine, they are both fiberglass. The only difference is that the doors are flat and my siding is ribbed.

donn said:

TAKE IT BACK.
Go to an automotive paint store, explain what your dealing with and get their recomendation.  Painting fiberglas can be a challange.  Doing it right is not cheap or fast. 

Click to expand...

I wasn't looking for either. This paint is advertised to be compatible with fiberglass. My local auto paint store was full of younger guys that only worked on sheet metal, so they couldn't give me a good recommendation.

I would go to a west marine...or boating store... for marine paint products...

that said, I would guess that the stuff you were sold will work ok.

Before we left Arizona the 1st. of April, we sanded down and painted the very faded decals on the side of our fifth wheel. When done, we sprayed over the new paint with clear coat. The paint is jet black. Turned out very nice and we got compliments from other people in our park. We were happy with it as well, we will see if the paint is on the ground when we return in October, I doubt it.


Bill

billwild said:

Before we left Arizona the 1st. of April, we sanded down and painted the very faded decals on the side of our fifth wheel. When done, we sprayed over the new paint with clear coat. The paint is jet black. Turned out very nice and we got compliments from other people in our park. We were happy with it as well, we will see if the paint is on the ground when we return in October, I doubt it.

Bill

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Bill, what kind of paint did you use?

Cerd.
    I just remember that it was an exterior paint that was good to use on fibreglass. Wish I could help more than that. I know it was not plastic paint as we looked at that and did not go with it.


Bill

If you have exposed fibers you should brush on some fiberglass resin to soak in and bind the fibers. Then you can sand and prime over it. You will want to get rid of the chalking before priming. While the urethane will stick to most surfaces, the cleaner the better. A good paint job is 85% preperation.

I repainted my motorhome and decided to do it right. After much research I went with Eastwood automotive Urethane Primer Surfacer and Single stage Urethane Paint. Painted decals also with same but had sparkle added to paint
The key though to any good job is preparation. Hardest part was getting that damn Ploy Glow off. I really hate that shitty stuff

boatbuilder said:

If you have exposed fibers you should brush on some fiberglass resin to soak in and bind the fibers. Then you can sand and prime over it. You will want to get rid of the chalking before priming. While the urethane will stick to most surfaces, the cleaner the better. A good paint job is 85% preperation.

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This primer is advertised to paint over the chalky surfaces without issue. I am doing a few test patches before I paint the whole thing.

Wizard46 said:

I repainted my motorhome and decided to do it right. After much research I went with Eastwood automotive Urethane Primer Surfacer and Single stage Urethane Paint. Painted decals also with same but had sparkle added to paint
The key though to any good job is preparation. Hardest part was getting that damn Ploy Glow off. I really hate that shitty stuff

Click to expand...

That's pretty much what this is, a urethane modified acrylic primer/sealer/bonder. https://www.rustoleum.com/product-catalog/consumer-brands/xim/bonders/advanced-technology-uma-white/
I just have stripes painted into the siding. I am going to paint over it and add some stripe vinyl decals from my local RV dealer.