Does all the old butyl tape need to come off?

Since I was in a hurry and my shop Got a case of butyl delivered for our shacks I ended up doing like the factory with butyl underneath and over top each screw

sasq40 wrote:
Yeah I tore it all down and have all the vents ripped off. Just grabbing some mineral spirits and plastic scrapper to get the old stuff off. The old sealant was butyl on the bottom edges and it was overlapped on the edge over the screws. Is that still the best option? Local rv place doesn't carry eternabond, only stuff they have is 4" x 25' for 100$

Yes, careful with the mineral spirits on rubber roof.
Since youve gone to effort to remove vent, lapping with tape, eternabond etc, not needed. Using butyl tape under flange is best under the vent. (butyl shouldn't lap over onto top though),
Normally what butyl squeezes out after a while is trimmed off, then perimeter and screws are liberally caulked. Dicor self leveling on rubber roof is the more common used.

SidecarFlip wrote:
I use Sikaflex myself. My Home Despot carry's it.

Even I used coulks professionally, I yet have to find one that last on RV. Boat coulk hold well, but turned yellow after 1 year.
I've been using polyurethane roofing caulk on other jobs as black doesn't match RV and it is good stuff, forming rubber-like after drying and with good adhesion.
Lately found white version at HD sold as window caulk, but my experience with it just started.
For roof coating the $200/bucket white stuff at HD looks very good and comes with lifetime warranty.
Still thinking who's life it is.

I use Sikaflex myself. My Home Despot carry's it.

And a FYI the eternabond has only been on for two months as I tried to do some preventive sealing before my kid came. So there isn't any noticeable damage from the water, it's been a dry summer with a few exceptions

I had issues with Eteranabond on my Fleetwood where PO slapped it over damage and the thing not sticking all the way around - created water pockets that directed water into the cracks.
My Lance on other hand - had very heavy layer of butyl tape all around. It looks ugly as the butyl overflows the joint and I am scraping it when it forms droplets, but the joints don't leak.
I don't see any aging on butyl, so if the old one is clean, I would just add more tape on top and squeeze the excess out.
Also Lance roof had some kind of liquid paste applied around roof opening, that forms 2" wide stripes over each trim. .
I could not find what is it, but it is holding very well.
Have no idea if this is how Lance sealed the camper at the factory, or PO redid it, but on 16 yo camper the only water intrusion was via slide awning screws, where they "forgot" to apply any sealant.

Yeah I tore it all down and have all the vents ripped off. Just grabbing some mineral spirits and plastic scrapper to get the old stuff off. The old sealant was butyl on the bottom edges and it was overlapped on the edge over the screws. Is that still the best option? Local rv place doesn't carry eternabond, only stuff they have is 4" x 25' for 100$

Be careful of assuming that as sticky as EternaBond (EB) is, it is not all it is cracked up to be if installed wrong. I learned the hard way as mentioned in THIS THREAD REPLY

As shown in that link, I wrongly assumed that EB would adhere to the flange of the roof dome bubble- it did not, but it sure fastened to the existing roof!!! For EB to really seal, it needs to have a mostly flat surface and I assume it will not stick to butyl tape (BT.) If there is a "mass" of BT under EB then there might be the possibility of "fold crimps" of the EB at its edges... you do not want this. But even if the edges of the EB over BT are nice and flat, there will always be some sort of putty pocket under it.

Believe me, once EB is stuck to materials of which it is compatible, it is very, very tough to remove!!!

sasq40 wrote:
What's the proper process to reseal the roof vents.

Remove most the butyl then re butyl? Remove the vents completely, or what?

I will not trust EB to seal against anything but the roof itself. In the link I posted above, it was an effort to do some preventative maintenance on the roof components so as not have to continuously inspect and do surface prep and seal them. To answer your question, I would recommend taking the time to scrape away any loose material, thoroughly clean and use a decent sealer. Many folks recommend a specific RV sealant. But, I have to go through the whole process of maintenance of which I was trying to reduce with these accepted products. I am now using THIS PRODUCT.

If the vent is needing most or all of the surface sealant removed then perhaps re-butyl'ing might be appropriate. I ended up doing just that for my recent repair to correct the botched job in the first link above. EternaBond it almost nearly impssible to remove without a LOT of work. I did it as well as installing a new roof item with new butyl tape and then sealing properly over the whole assembly. See the results here:
Repaired the roof, replaced the bubble dome...

In that repair thread, you can see the old bubble and crank-up vent; the after images show the proper repair job as well as new sealant over the vent. The vent seal was maintained per the procedure I described.

I do not knwo what the OP's exact situation is, but from the little description Me believes that there is some significant work in the future to correct the EternaBond band-aid.

Not sure about whether Eternabond can bond to butyl tape - but that shouldn't be an issue as any butyl tape that squeezes out after instal of vent/window etc is usually trimmed off. My experience has been that Eternabond will bond with just about anything except silicone. Make sure the area is dry - prep it in accordance with Eternabond instructions - and make sure you use adequate pressure (metal roller recommended) when installing.

Personal opinion of one internet stranger: To do it right, you would need to take off the vent, remove the old sealant and Butyl as well as possible from the vent frame and the roof in order to get clean surfaces that will seal well, and put the vent back on with new butyl tape and probably self leveling sealant on top.

In the process you may or may not find that water has been getting in for a while and there is some internal damage to the roof structure.

For a quick fix ... maybe put a good helping of self leveling sealant around the outside vent frame and hope it seals it up until you have time to do it right. It needs to be reasonably dry for this to work...

Other opinions welcome, please