Holes in Fiberglass Roof

Gdetrailer wrote:
Unfortunately, I myself have found that FRP doesn't hold all that well when used for roofing applications.

I used FRP to replace a aluminum roof that the previous owner shot thousands of air nails through as they attempted and failed a rehab of that trailer. The FRP performed well for me for about 7 yrs but after that it started cracking and tearing it's self apart in places with no rhyme or reason..

I don't know the history of this RV except that prior to me purchasing it a year and a half ago, it was set up permanently in this location in central Florida for 7 or 8 years. During the winter the roof is shaded for part of the day by pine trees, but it is in full sun the rest of the year.

When I inspected the roof after purchasing it, I discovered two locations where water had wicked under the FRP and rotted out the plywood, but the color and texture of the entire RFP was uniform then, as it was when I last washed it about three months ago--there wasn't the slightest evidence of any deterioration of the RFP. I'm positive I would have discovered any discoloration or cracks at that time because I cleaned every inch of the roof while on my hands and knees.

Gdetrailer wrote:
For yours, the discolorations look to be rust color to me.

The rust could have come from the substrate layer via staples or other fasteners used to fasten the substrate to the roof framing.

But to get that rust to bleed through it would mean that the cracks developed over time and allowed water to slowly seep into and though the FRP layer..

One of the two soft spots where the plywood has rotted due to water wicking into the FRP's fabric spans a couple of rafters, and yet the color of the surface is uniform--there is no evidence of any rust bleeding through or any cracks despite the RFP having sagged slightly due to lack of support.

I agree, the color of the spots in the picture in my original post certainly looks similar to rust, but the nearest truss is at least a half foot away. And when I look closely at the first picture (I've enlarged part of it below), to me, it does not look like rust that has wicked up through the RFP's, and the cracks seem to imply the consequences of some type of stress.


Click For Full-Size Image.

However, how does that explain the second spot which I discovered because of the discoloration? There are no cracks whatsoever, and as I mentioned, that small area was so soft that when I scratched at it with my fingernail the FRP just disintegrated. However, the same scratching a few inches away only resulted in a barely noticeable indent, and I can not find a similar spot anywhere else. The whole thing remains a mystery to me.

Gdetrailer wrote:
I have found that FRP top layer sheds moisture well, but once the top layer erodes some the moisture can be wicked into and through the FRP and into the substrate under it that it is glued to..

Once the raw fiberglass under the top layer has been exposed to UV from sunlight, it tends to breakdown, gets brittle and flake off.

Discounting these two spots, I can find no evidence the top layer of the FRP is deteriorating and therefor reaching the end of its life. But, the inherent weakness of these types of roofs, namely the constant maintenance, is encouraging me to look closely at roof systems such as Crazy Seal and RV Armor because those products seem to be integrated systems rather than a series of band-aids like that of a typical RV roof.

Unfortunately, I myself have found that FRP doesn't hold all that well when used for roofing applications.

I used FRP to replace a aluminum roof that the previous owner shot thousands of air nails through as they attempted and failed a rehab of that trailer. The FRP performed well for me for about 7 yrs but after that it started cracking and tearing it's self apart in places with no rhyme or reason..

It seems as if the FRP isn't suitable for extreme tempurature swings from winter time into summer time here in PA.. Typical winters we can get below zero temps for weeks at a time and in the summer, 90F in the shade for weeks at a time.. Mine doesn't have shade so summer roof temps easily can go over 120F on hot days..

For yours, the discolorations look to be rust color to me.

The rust could have come from the substrate layer via staples or other fasteners used to fasten the substrate to the roof framing.

But to get that rust to bleed through it would mean that the cracks developed over time and allowed water to slowly seep into and though the FRP layer..

I have found that FRP top layer sheds moisture well, but once the top layer erodes some the moisture can be wicked into and through the FRP and into the substrate under it that it is glued to..

Once the raw fiberglass under the top layer has been exposed to UV from sunlight, it tends to breakdown, gets brittle and flake off.

My fix to the problem was a new roofing material that can deal with the extreme expansion and contraction that happens with thin FRP (fiberglass in general has a large expansion/contraction ratio with large temp swings).. I applied a product called "Peel and Seal" (has a thin aluminum skin as a top layer to protect the rubber) over top of the existing FRP.. So far has worked well for 5 yrs for me..

I wished I had better answers for you..

Thank you for the responses.

I really am trying to understand what is happening with my roof. I realize it is about 17 years old, but I was under the impression the fiberglass would last much longer. Thanks to Gdetrailer I now understand it is not a typical fiberglass panel but rather FRP, which undoubtedly explains why I can indent it with my fingernail.

However, with the exception of these two spots, I can find no evidence the FRP is failing in the way I've seen what happens when rubber roofs reach the end of their lives. Instead, the surface looks uniform and it takes about the same amount of pressure to create a small indent with my fingernail at the numerous random places I've tried.

I am still curious about the reason for the cracks and discoloration when I know there was no evidence of any cracking only a few months earlier. We live in central Florida where we've only had 5 frosts in the last two years, and no hard freezes whatsoever. However, something rather unusual happened a week ago when lightning struck a driveway and a solar light mounted on an aluminum pole about 40' and 50' respectively from the location of this damage. As can be seen in the picture I took minutes after the strikes, pavers were hurled some 20' toward our RV, and one paver even ended up on the roof of our neighbor's motorhome.


Click For Full-Size Image.

I found small chunks of pavers on the other side of our RV and as far away as behind our neighbor's RV, and parts from the solar light were scattered over a much larger area. In fact, I found the solar collector panel intact, although barely recognizable as such, almost 120' from the light pole where it landed after falling through a stand of mature pine trees. (The bare area in the background is not associated with the lightning strike but rather an area I'm preparing for sod.)

Although I could find no evidence the lightning struck our RV, maybe some hot debris from the pavers or solar light landed on our roof. Anyway, the damage has been repaired with Eternabond, so I can now turn my attention to trying to figure out what is the best way to extend the life of our roof without the constant hassle of periodic maintenance because we intend to keep this RV for many years.

A coating of ProflexRV will seal and protect.

Epoxy works or caulk. Easy fixes don't have to outsource. Go to Lowes or Home Depot and take care of it. Go up on the roof periodically to wash it and inspect, Go RV.

HarryB1 wrote:

theoldwizard1 wrote:
If this is truly fiberglass, then it is built like a boat, probably like the deck/roof; resin and 'glass over plywood or foam core.

My guess is that those spots are "dry spots" where the 'glass was not thoroughly wetted. It should be repaired using the same steps you would for boat repair. It dies seem odd that a fingernail can dent it as fiberglass cures very hard.
(snip)

The roof is not constructed like a boat's hull, but rather has a thin layer of fiberglass which is bonded to a fabric backing with a total thickness of about 0.030". When I was replacing the skylight I had to be very careful as I was removing the old caulk to not puncture the roofing material because it is quite flexible, and I did puncture it in one spot.


Click For Full-Size Image.

Known as Fiberglass Reinforced Panel (aka FRP) which is a thin plastic (polyester resin) material with fiberglass fibers in the material and it typically glued to wood or foam substrate.

Typical fix is using Polyester resin/fiberglass materials and techniques.

It is also referred to as "Filon" which is a brand name..

FRP material for RV roofing

The website above also has Maintenance and repair manual HERE which you may find helpful.

Roof application can be a bit problematic to repair since the repairs must be able to withstand large expansion/contraction cycles from large temperature swings. The repair manual mentions "two part flexible spot filler", not all over the counter fillers sold in retail stores are flexible so you might want to check with a autobody shop that deals with fiberglass repairs or a boat shop..

It’s old crusty and sun cooked. Patch em up with something overlaid over the surface and either deal with it or sell it.

theoldwizard1 wrote:
If this is truly fiberglass, then it is built like a boat, probably like the deck/roof; resin and 'glass over plywood or foam core.

My guess is that those spots are "dry spots" where the 'glass was not thoroughly wetted. It should be repaired using the same steps you would for boat repair. It dies seem odd that a fingernail can dent it as fiberglass cures very hard.
(snip)

The roof is not constructed like a boat's hull, but rather has a thin layer of fiberglass which is bonded to a fabric backing with a total thickness of about 0.030". When I was replacing the skylight I had to be very careful as I was removing the old caulk to not puncture the roofing material because it is quite flexible, and I did puncture it in one spot.


Click For Full-Size Image.

micro cracks that allowed water to get below the gelcoat. Freezing expanded the water to ice and the cracks got bigger. as freeze thaw cycled this what eventually happened. Go as deep as necessary to solid material then re-glass.
Or, if you can find a boat repair shop willing, have them do it professionally. That would be my choice because falling off the roof an anything is not a good thing to happen to a geezer

HarryB1 wrote:

This second picture shows an area some distance away where I discovered a brownish spot similar in color to those in the first picture, but there were no cracks. I began to scratch at it with my fingernail, and after discovering the surface felt soft, it came off with very little effort, resulting in this hole.

The rest of the surface of the roof seems to be quite solid. I can put an indent into the fiberglass with my fingernail, but nowhere does it feel soft like it did at this spot.

Is this an indication the whole roof is beginning to fail, or something else?

If this is truly fiberglass, then it is built like a boat, probably like the deck/roof; resin and 'glass over plywood or foam core.

My guess is that those spots are "dry spots" where the 'glass was not thoroughly wetted. It should be repaired using the same steps you would for boat repair. It dies seem odd that a fingernail can dent it as fiberglass cures very hard.

DO NOT COAT YOUR ROOF ! Take it to somewhere that does 'glass boat repair. Worst case, part of the substrate/ core material will have to be replaced then layers of resin and 'glass applied.