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I bought a used round-top 24ft cargo trailer that I shall slowly convert to my rolling home. It has an issue or two, but the price was awesome, so I pulled the trigger on this baby.

One of those issues, however, is a leaky roof. A damaged, leaky roof. A very poor sheet metal patch to some sort of impact is evident even from the ground, with no apparent caulking or adhesive having ever sealed the edges. Perhaps a tree branch fell there at one time? Who knows?

I'm going to address that particular area with specific attention. But when done, I'll want to apply some sort of roof sealant/coating to the entire top, to help ensure I am also sealing anything I can't yet see. 

I already researched online for "the best" top coating possible. Thinking something like Line-X bedliner might be the answer, I investigated various polyurea-based coatings and found RV FLEX-ARMOR. While I am convinced they truly are the best possible coating I could ever have put on my roof,...the price quoted was over $4000!!!! That's $1000 more than I paid for the trailer!

So I know there are many roll-on roof sealing products,...but its a dizzy array of elastomers vs latexes vs rubberizing blah blah blah. 

Can the experienced folks here who have had to coat their roofs give me advice and the benefit of their stories?
lowes has a fiber roof coating made up of tar fiber silver paint. I have used many times and it always worked for me.
Wow,...only one reply?

I figured y'all would have more experience than this.
Okay I'll give it a try but first there are several different materials used to make a roof and several ways to attach them. They all expand and contract differently. What is the roof made of and how is it attached? If metal what kind and how thick? Glued,screwed or riveted? How large an area was damaged? What is it mounted to and how far apart are the supports? Several pictures of inside and outside would be helpful. The year ,make and model also helps. How often do you want to have to repair or recoat? Is the rest of the trailer water tight? How long do you plan to keep or use the trailer. I would assume there are roof seams on a trailer this size and if so how many and what kind. Do you intend to coat the whole roof or just the section that was repaired. Do you want it to look pretty? The reason I imagine many have not replied is because no one is sure what you are working with and no one here wants to tell you something that might not be correct. There is a large variety of products because of the large variety of different roofing materials and different ways they are used. Many cargo trailers come from the factory with leaking roofs and just about have now way short of replacing/reinstalling them to get them to stop leaking due to the way they were designed or installed.
If it is just the patch that is leaking you don't need to coat the whole roof. Just remove the patch and install it with one of the Sikaflex, permanent adhesive sealants under the edges of the patch and when it dries add some caulking on top all along those edges if you wish to take a belt and suspender approach. If you have leaking seams then caulk them.

You really only need to coat the whole roof if the metal is so old that it has pinholes all over it.
Those answers do help. Thank you. I'll try to get up top and take some pictures to share with you in the next couple days,...then see what folks have to say.
(10-02-2019, 01:31 AM)Pleasant Travels Wrote: [ -> ]Those answers do help. Thank you. I'll try to get up top and take some pictures to share with you in the next couple days,...then see what folks have to say.
Not sure what material is your roof, but if I think fiberglass is the most durable solution, if you know (or can learn) how to use it. In my sailing days, it was the go to material, waterproof and long lasting. Here is a video to get an idea what's involved.
You will need resin, hardener and fiberglass cloth (or bondo and fiberglass form Walmart) and sandpaper. Do that outside because it stinks to high heaven. Cheers!
As promised, here are some pictures from the roof.

Here you can see that the aluminum skinned roof was not coated entirely, but only over the seams and the screw heads that fastened the panels down. You can also see it is plainly peeling and chipping and wearing away. This trailer was built in 2003, so this sealer, whatever it was, is 16 years old. Judging from the rotted interior ceiling panels of luan plywood, I guess the sealer started failing after 10 years.

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There is also at least one previous scar from getting bashed by a tree branch or something on the fiberglass cap that covers the leading edge of the roofline on the V-nose portion. Perhaps something as simple as spray on FlexSeal will seal this?

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And here is the very crude sheet metal repair someone did at some point in the past. Again, probably a tree branch bit of damage. Notice no one ever bothered to even try to caulk it or seal it in any way?! Egad!!

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As I was pulling down the rotted water-damaged interior ceiling luan paneling where this patch was done, out started spilling the contents of a LARGE rodent nest that got sealed up inside when the repair was done. Whomever did the patch likely could not see the rodent nest when they sealed it in that unknown number of years ago. Fortunately, whatever squirrel or roof rat had made the nest was gone and out of there when it was done. No petrified carcasses in there, thank God. But you can see the fist-sized hole that had been the issue.

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From looking at the pictures I would consider getting a single one piece aluminum sheet if possible and replacing the entire roof. I helped a neighbor with a large 5th wheel camper do just that years ago. He was able to source a large rolled up piece that we used edge trim pieces to hold it at the sides and with today's glues and sealants I would think you would be able to glue/seal it to the roof ribs. The fewer holes you put in a roof the less likely it is to leak but you do have to consider expansion with aluminum. If you do try to reseal it all of the old sealant will have to be removed and that is a big job most times and every screw hole needs to have sealant in/on it.
Really interesting thread to see for me just moving forward, as I have a relatively new trailer but it is constantly getting bombarded by acorns, plummeting squirrels, and the occasional falling branch for an oak tree directly overhead. I'm waiting in terror for that one big branch to fall .. and one day I will surely have to put some serious money into this roof ...
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