Cracks on the roof. Please help, pretty please.

[DavieBoot]

Hello forum,

Second post this week, I should start a build jounal..I always mean to and then forget about it.

So a new problem has popped up with our TTT this week. We are building a moc-T@B and are having problems with the rear roof cracking.

The roof consists of: frame, interior skin(luan), spars, insulation, plywood(1/4") coated with three coats of CPES(Raka) and then painted with Rustoleum marine primer, and three coats of navy blue gloss topsides paint.

What I think is happening is that the roof cools off during the cool nights in San Diego and then is rapidly heating up in the sun and cracking. The cracks aren't just on the paint. The paint/primer/epoxy is adhered really well to the teardrop, and the cracks are pretty much only on the back of the roof(the part that's exposed to the sun).
Is this theory crazy?
Any other thoughts on what it could be?
Any ideas about what I can do to fix it?

This thing is so so close to being done, and now I am almost completely defeated by this problem. My boyfriend and I are planning on using this for a two-month roadtrip, skiing in the mountains. We don't want snow and ice getting into the cracks and destroying the roof.

Please please help me!
Thanks
Ashley

[kirkman]

You will get allot of opinions on this I am sure but what I would do for a quick fix is Paint it with this.
http://www.snowroof.com/product_detail.asp?product_id=SR104
Or this.
http://www.koolseal.com/product_detail.asp?product_id=63-600
They are made by the same company. You can ether sand off your paint and then apply it, or apply it right over your paint. It only comes in white but the stuff works GREAT it expands and contracts with out cracking I have had it on my coal ash trailer for 5 years now with no leaks. It comes in gallons and its cheep under $35.00 a gallon.

[DMcCam]

Hi Ashley, would you post a picture of the damage for us? Are the cracks through the first layers of the plywood or just the finish on top?

Dave

[DavieBoot]

Dave,

Thanks for the response.

I'll take a photo in the morning. The cracks are through part of the first layer of plywood. The finish on top is adhered really well to the plywood, it's for sure the wood, not the finish. Which is unfortunate.

[DavieBoot]

The cracks are thin (1/32" or less) horizontal cracks extending a few inches each. But there are lots of them, spaced anywhere from a few inches to a couple feed apart. Looking in, you can see that both the paint and the primer is split.

[Gage]

Your ply is what's causing everything. 1/4" is too thick. You should have used 1/8" ply. After all, you’re not building a house and I'll bet you have no plans on carrying an Elephant on the roof. 1/4 inch will give you nothing but troubles unless it's a flat surface. Like that, pictures will help pin point the problem.

[afreegreek]

you need to post some close up picture for sure or all you'll get is guesses..


my first guess is you have WAAAAY to thick of a coating on poor grade ply bent around too tight a curve.. the biggest mistake I see people make with paint and other rigid coatings is putting on too much.. thicker is not better..

[DavieBoot]

Okay here are some photos. I'm not sure it's because the coating was too thick. As the area where the cracks are actually was missing a coat of paint. And since it's marine paint it's supposed to be able to expand and contract.

There's one more part of this mystery that I haven't mentioned. The trailer has a liscense plate on it, and the area under the liscense plate has no cracks.

Okay so here goes:
[img]
http://tnttt.com/album_ ... 13d42a4343[/img]




[img]
http://tnttt.com/album_ ... 13d42a4343[/img]


I"m so very appreciative of the help!

[Gage]

How about giving a wider shot and mark where the cracks are with a marker of some kind. Those pictures you have posted looks like they are cracks with the grain.

[mikeschn]

I would apply a membrane on the roof. Canvas, or fiberglass. Use the same paint that you used the first time.

Put down a layer of paint, put down your canvas, and then another layer of paint.

Mike...

P.S. You can join us in the foamie section to see how this works...

[dave_dj1]

The problem is you probably used 1/4" A-C plywood, it's made from southern yellow pine, (probably the most unstable wood known to man). I think the ply wasn't dry and has shrunk thereby causing cracks. I see it all the time if we use 3/8" finish ply on soffets.

[H-Balm]

mike's idea seems pretty sound.

[DavieBoot]

I would apply a membrane on the roof. Canvas, or fiberglass. Use the same paint that you used the first time.

Put down a layer of paint, put down your canvas, and then another layer of paint.

Mike...

P.S. You can join us in the foamie section to see how this works...

Mike, can you point us to a thread where this is discussed? We tried the elastomeric roof coating, but got very poor adhesion with the underlying paint, so it just peeled and tore.

[DavieBoot]

You will get allot of opinions on this I am sure but what I would do for a quick fix is Paint it with this.
http://www.snowroof.com/product_detail.asp?product_id=SR104
Or this.
http://www.koolseal.com/product_detail.asp?product_id=63-600
They are made by the same company. You can ether sand off your paint and then apply it, or apply it right over your paint. It only comes in white but the stuff works GREAT it expands and contracts with out cracking I have had it on my coal ash trailer for 5 years now with no leaks. It comes in gallons and its cheep under $35.00 a gallon.

How did you get it to adhere to your roof? Ours pealed right off.

[Larry C]

If it's only in high stress areas, I would consider scraping the paint off down to the wood with a good carbide scraper. Sand it thoroughly so only bare wood show. I would then apply fiberglass and epoxy patches where needed. Fill coats of epoxy will fill the glass weave, and allow you to feather the edges so it will blend without showing. Prime & repaint.

Larry C