Putty tape under roof fold over?

How much working time do you get with butyl caulk? Are you talking just a pure butyl gutter caulking available at home depot, or the less available brands recommended here for sealing on top of the rail?

i too am going to add some kind of insurance under the roof skin fold over, but i think most of my effort to weather proof will be spent at the roof penetrations and windows since i gather this these areas are a more common source of water damage.

i'm very interested in seeing the consensus on how to better seal this wall roof seam.

has anyone tried the use of tyvek (or another competitor) sill seal tape that is used to seal around the house wrap where it meets the doors and windows of a residential dwelling. unless i'm missing something, why wouldn't you use this tape to seal by overlapping the wall skin by 1/2" and the other edge of the wide tape to extend over the curbing/rafters/house wrap; then cover with roof skin and putty tape as normal? this same procedure could be used to seal the walls up at the windows and doors. it seams like this would work better than just the putty tape alone.

This will definitely help seal the vapor barrier but will do nothing to help prevent water from getting under the metal skin. Pulling a trailer in the rain at 60 mph will create strong hydraulic forces. If enough water gets trapped between the skin and vapor barrier it can eventually migrate and find a way in. IMHO, if you are going to take extra measures, it's best to do so in a fashion that will help keep the water on the outside of the metal.

I replaced the putty tape in the '70 16SC.  It was tougher to get good photos of it than it was to replace.

This is the old putty that was under the J-rail, and the stuff under the fold was just as dried and useless.



I figure it this way...  if the putty tape was good enough for the manufacturers to use 50 years ago, and the trailer is still standing 50 years later, then it should be good enough to use now.

I did not completely remove the roof, but rather took it loose one side at a time, removed the old tape as cleanly as possible without slicing fingertips off, and then cleaned both surfaces, under the lip and the face of the siding, with denatured alcohol. 


Regular putty tape, not butyl, in a 1/8" thick by 3/4" wide size kinda forced into the crease of the roof, then push the roof back into place.  I took a rubber mallet and gently tapped the whole edge from end to end, until the nail holes were pretty well lined up then nailed it into place.  That squeezed the putty firmly into place.  I trimmed the excess tape away after the nails were all in place.

Adding the putty on the back of the J-rail and replacing that drew everything back into perfect...well, almost....shape.  I have no doubt that it is going to hold up as long as the rest of the job, for 15 years or so, when it all should probably be replaced again.

I don't like putty under the roof bend but some sort of sealer might be OK. The metal folds better and has a tighter lip without putty. To me, putty after the orig. construction does lift the lip and could cause problems.

I use gutter seal after staples/nails and do it twice. New putty on the J/awning rail will seal it after seating the top of the rails with a rubber hammer.

I recently finished a trailer with a long side seam and was worried about leaks since that seam had been a real leaker/rot producer. I planned on real butyl tape at the seam edge (tightened by siding screws) but wanted extra insurance:

The roofing company sold me a specialty caulk that had medium stretch. (other options were super flexible and low stretch) The caulk was water cleanup and caution on the label stated, "do not use paint thinner to clean the surface". A bead of caulk went behind the butyl tape, about 1/2", the length of the seam. No real way to tell if this caulk was worth it, since the butyl is the first defense.



The same caulk was used in a rear roof trim gap and was very nasty to work with. (I had slipped new metal up under the roofing about 10". Then the roofing laid over and secured with trim. The gap was at the bottom of the trim piece after putty and screws) Smoothing was a nightmare, it was ugly and smeared along the metal. Took over an hour to do that one rear seam. One reason for using it instead of OSI is the size of the gap and ease of application. Ha. Didn't quite work out that way...



Roof metal overlapped. After stapling, all divots and old holes sealed with OSI. Waterproofing tape on the underside.



Here's the underside of the trim, sorry it's hard to see.



Anyway, I did use OSI at the side seam after screws with the putty well seated. It smoothed perfectly and was so invisible we used a side light to be sure the seal was complete. I'm confident the trailer won't leak and will not be using specialty roof caulks again.