Roof inspection on potential new buy - Fiberglass RV


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Old 10-16-2011, 01:20 AM   #1
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Name: Chris
Trailer: Looking
British Columbia
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Roof inspection on potential new buy

Hi There,

I am have been reading around here for the last little while. We are currently looking for a used trailer, and I am hoping to get a 17 foot Fibreglass one. I am currently looking at a big foot, and my main concern is water damage.

The owner said that the roof vent leaked at one time, I believe with the previous owners. He was thinking they left it open, but I doubt that. I have attached a picture they sent me of the ceiling as was hoping to get some input on it before I go and see the unit myself.

I plan on giving the whole unit a good once over, looking inside all the cupboards, under bedding, underneath. Pressing on the fibreglass inside and out to look for any movement, or soft spots. I also hope to run a hose over it to see leaks, but I am more concerned about any existing water damage. I don't mind patching up some spots.

Any advice on the picture, or techniques to spot water damage would be greatly appreciated. I don't mind fixing the mechanicals, but want to stay away from having to tear the unit apart.

Thanks in advance.

Chris
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1979 Bigfoot Vent.JPG  
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Old 10-16-2011, 10:02 AM   #2
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Name: Martin
Trailer: Trillium 4500 1977
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Hi Chris,
From inside, you may find insulation sagging, it can be reglued with Contact Cement. The roof vent is easy to inspect and prevent from the outside. I use Kool Seal roof coating Kool Seal Roof Coating - PPL Motor Homes to create a flexible and durable membrane between the roof vent flashing and fiberglass, so there is a smooth and continuous joint that will last for years. Warning: Such stuff will not stick on asphalt based compound. The rubber gasket under the lid only needs to be even and reasonnably air tight. I use the same roof coating to seal the flashing that protects the top of the door. I later paint it to match the rest of my Trillium shell.

I really appreciate to have the roof vent opened most of the time, under rain or sunshine, so I also use a vent cover similar to this one: Maxxair II | Latest. All is needed for installation: drill four holes into your flashing to hold the bracket but use some nylock nuts, not plain nuts that will end up flying out from vibration.

It is also advisable to shut the vent and all windows on the road because vibrations may damage the fragile opening mechanism. Under very warm climate, some of us even install units with 12V ventilator or even Air Conditionning unit. This is another ball game, because you would have to plan for electrical power.

See details on the other thread Ducted air or Fantastic fan
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Old 10-16-2011, 04:31 PM   #3
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Quote:
Originally Posted by Chris Topher View Post
I have attached a picture they sent me of the ceiling as was hoping to get some input on it before I go and see the unit myself.

Any advice on the picture, or techniques to spot water damage would be greatly appreciated.
Check out bf_odds_ends, especially the 5th photograph, which shows a cross-section of a Bigfoot roof where the vent had been removed. The way I would inspect it is to feel the wrinkled area for softness or squishy-ness. I would ask to remove the vent's trim to see if there's still dampness behind it. If it's dry, then only the thin inner surface needs to be replaced.
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Old 10-16-2011, 05:51 PM   #4
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Name: Martin
Trailer: Trillium 4500 1977
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Plywood core and potential hidden rot on roof ???

Quote:
Originally Posted by Frederick L. Simson View Post
Check out bf_odds_ends, especially the 5th photograph, which shows a cross-section of a Bigfoot roof where the vent had been removed. The way I would inspect it is to feel the wrinkled area for softness or squishy-ness. I would ask to remove the vent's trim to see if there's still dampness behind it. If it's dry, then only the thin inner surface needs to be replaced.
Thanks for the pictures, very informative for me too.
From the inside, the Bigfoot picture looked very similar to mine.

That means water inflitration can cause ROT on the plywood that is under the fiberglass shell In the case of the Bigfoot fan upgrade, I suspect the small opening has been cut larger to accomodate the new equipment. Someone who has an original Bigfoot may be able to confirm if the foam and plywood core is exposed like that or fiberglassed before the original opening is installed. That would make a big difference. If OEM dome has not been changed (what the picture suggested) there is a chance the foam and plywood core were protected from leaks. If not, you are talking of potentially wet core and major renovations. This is often the death sentence on sailboats when the deck core gets wet and rots.

Thanks for pointing out the structural and insulation difference between a Bigfoot and my Trillium 4500 which does not have a foam core like that. I don't know for sure if mine has any plywood core on the roof. I found out there is plywood core on the bottom part behind the propane tank. This leads me to beleive it there is likely some 1/4 plywood core on horizontal sections of my roof, but I don't know for sure.

I will check to see if there are any similar pictures of a cut trough a Trillium 4500 roof. I'm now concerned about Gord's roof damage. Roof damage, Triliium #136 If his roof has such wide cracks, everything is fine if there is no wet plywood under the cracks. Otherwise, there may be more extensive damage and potentially dangerous weak structural points on his roof. Patching a solid fiberglass shell is trivial, performing repairs on a plywood wet core is a far more complex and extensive operation.

Anybody who can tell about structure of a Trillium 1300 or 4500 roof, please let me know (with or without plywood core?).

I'm also surprised by the fact my roof vent appears to be installed differently than the description on the following thread: How to seal roof vents properly
There is no visible edge or any fastener on the bottom of the vent flashing, just a smooth and perfect seal with the Kool Seal I mentionned (performed by previous owner). Considering the effect of direct sun on butyl tape, I prefer it the way it is. Kool Seal produced a permanent, flexible and seamless joint, painted the same color as the shell.
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Old 10-16-2011, 07:40 PM   #5
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Trailer: 1979 13 ft Boler, 1987 & 1988 Bigfoot 5th Wheel
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The roof construction on Bigfoots depends on what year it is. The earlier ones do not have plywood in the roof. They are the outside fiberglass, 1" of foam insulation, and the the inside paneling all glued together. Those roofs have a tendency to delaminate/unglue.

I don't know what year they changed the construction and added the plywood layer.
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Old 10-16-2011, 09:14 PM   #6
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Name: Chris
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Thanks for the replies. I had seen that photo of the cross-section.

This is a 1979, which I think is the first year for Bigfoot, so I am assuming it won't have the plywood. I will be sure to take the vent trim ring off and inspect that area. After that if it looks dry, the rest of the panel board and foam seems dry and rigid, and the outside seems ok then I will have to assume there is no water damage.

Any other signs of the glue Delaminating? Does the fiberglass shell tend to bubble?

I am looking at the unit tomorrow night.
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