Repairing small cracks in Fiberglass roof.

[Walter Parr]

In doing my Roof sealing, using the procedure here using the Rust-Oleum Marine paint, but using their Primer 1st as added protection. I found 2 small cracks. What would be the best way to repair them before painting?

[Steve Huber Co-Admin]

Walter,
They look like surface stress cracks that may not cause any problems. However, if you want to be sure no problems arise, I would use self-leveling Dicor since it's on the roof and not visible. It's also flexible. If you do this, apply the Dicor and let it dry before coating the roof, and the Dicor, with Rustoleum Deck paint.
Others here may have better ideas...
Steve

[Carl Boger]

I think the Dicor and then rustoleum may well be enough to fix this.  If you want something more of a permanent nature you can drill a small hole at both ends of the crack, and then v the fiberglass out along the crack on both sides with a grinder. A shallow groove is fine. Get some chopped fiberglass mat and resin and mix it together well forcing it into the v'd out area and both holes.  Smooth it out as much as possible leaving the mixture just proud of the roof top.  Once it is dried sand it all back flush and fill in any pin holes in the fiberglass.  You can stop here, or you can add another layer of cut fiberglass mat  and resin over the just repaired area smoothing and feathering the edges.  It would not have to be perfect since it is on the roof and not likely to be seen.

[James Morse]

Walter,
I am doing the roof on our 04 Marquis at this time as well; I plan to fix several of the cracks with a flexible epoxy caulk which is used to fix surface cracks in gel coat on boats.  The cracks I am speaking of are where the front and rear fiberglass caps meet the roof and exterior wall surfaces.  The transition of the roof to the wall is a radius and this is where the cracks need to be repaired, which are visible from street level. You prep the cracks as noted above and fill in the V channel with the flexible epoxy and then sand flush.  I spoke with the bodyshop manager at Beaver Coach Sales a couple of weeks ago and he said sanding, grinding, and filling the cracks with resin may last only a couple of years before the cracks start to reappear.  I am hopping the flexible epoxy will resolve this problem.  Hope my 2 cents might help?

[Mike Shumack]

 I plan to fix several of the cracks with a flexible epoxy caulk which is used to fix surface cracks in gel coat on boats.  The cracks I am speaking of are where the front and rear fiberglass caps meet the roof and exterior wall surfaces. 

The transition of the roof to the wall is a radius and this is where the cracks need to be repaired, which are visible from street level. You prep the cracks as noted above and fill in the V channel with the flexible epoxy and then sand flush. 

I have used this product (epoxy filler) on my coach. It is flexible after curing. Not too expensive either. You just need to grind the crack out a little, fill with epoxy, then sand smooth after its cured.
http://www.totalboat.com/product/thixo-flex-thick-flexible-epoxy-adhesive/

Here's a video on how to use it: (starts at 5 minute mark) https://www.youtube.com/watch?v=PwNNnK-XBMQ