Butyl Tape - All Not Created Equal

[SRD]

I ran across this article on butyl tape that some may find interesting and instructive. It's written for the marine crowd but still relevant to us RVers. After purchasing two rolls of so called butyl tape at separate RV stores my gut suggested that something was wrong with them. Apparently, some of the stuff available is not butyl tape at all and others contain fillers that reduce quality.

On this same note and after looking at some marine applications of butyl tape I now wonder why it's necessary to add a layer of caulk over roof penetrations, vents for example. It would seem that a good quality bed of butyl tape is enough of a seal. This

video on using butyl tape for deck fittings

is what gave me the idea. The mess that caulk makes is what drives my interest.

[GMike A]

Logic tells me to run a strip of butyl around the perimeter of the stanchion so that the entire object does not allow penetration;however, wrapping just the threads might be adequate. The above refers to bolt insertion holes and not rivets but is relevant. I have considered a little dab of butyl into rivet holes and then seal the snap cap with Lexel.

Does anyone chamfer their rivet holes if and when using Butyl?

[Carol H]

LOL a while back we had a big discussion on the topic of Butyl Tape and how to tell if what you purchased was are was not the real thing.

Here is the thread: Butyl tape question

[Raz]

A while back a member did a posting where he caulked the edges after he had finished the installation. I think it was a window. As I recall the purpose of the caulk was to stop the butyl from getting dirty. It certainly doesn't take long for the exposed edge to collect grime. Raz

[GMike A]

I remember reading the Butyl tape thread and how to tell good vs bad tape etc. I was wondering if anyone chamfered their rivet holes and dabbed in tape goo? I know some have suggested it (Donna I think) and someone dabbed silicone inside the actual rivet head hole (Francesca I think). So there are lots of thoughts on the subject.
Dont hold me to the I think people

[Carol H]

Originally Posted by GMike A

I remember reading the Butyl tape thread and how to tell good vs bad tape etc. I was wondering if anyone chamfered their rivet holes and dabbed in tape goo? I know some have suggested it (Donna I think) and someone dabbed silicone inside the actual rivet head hole (Francesca I think). So there are lots of thoughts on the subject.
Dont hold me to the I think people

Some people use a dab of butyl tape some use a dab of caulking but NOT SILICONE caulking - if you feel you have just got to use a caulking use something like Lexel which is not silicone.

[Donna D.]

I'd be more inclined to put a dab of caulk in the snap cap, than inside the rivet hole. YMMV

[Steve Hammel]

Plumbers putty might be a bit easier to work with for rivet holes.

[SRD]

Originally Posted by Carol H

LOL a while back we had a big discussion on the topic of Butyl Tape and how to tell if what you purchased was are was not the real thing.

Here is the thread: Butyl tape question

Yep, makes my post practically redundant. Thanks for the heads up. I really enjoyed reading the responses, especially toward the end of the thread.

[Frederick L. Simson]

Originally Posted by GMike A

Logic tells me to run a strip of butyl around the perimeter of the stanchion so that the entire object does not allow penetration...

Does anyone chamfer their rivet holes if and when using Butyl?

For this stanchion mount application, the through post hole needs a drainage path, so only the bolt holes need to be sealed. Any moisture that wicks into the crack between the mount and the stanchion will drain from the crack between the mount and the deck. The chamfer provides a void for the butyl to fill around the bolt threads.

If you're sealing the entire object, such as a window frame or tail light assembly, then the bolt/rivet holes don't require chamfering.

Originally Posted by SRD

On this same note and after looking at some marine applications of butyl tape I now wonder why it's necessary to add a layer of caulk over roof penetrations, vents for example. It would seem that a good quality bed of butyl tape is enough of a seal...

The mess that caulk makes is what drives my interest.

The mounting bolt holes around the perimeter of a Fantastic-Fan have huge chamfers in relation to the size of the heads of the bolts provided. You don't want standing water on top of the bolt head, for even stainless steel will rust under constant contaminated water exposure with enough time allotted. This is why you add caulk, but it is only necessary to cover the chamfered bolt heads.

[SRD]

Originally Posted by Frederick L. Simson

For this stanchion mount application, the through post hole needs a drainage path, so only the bolt holes need to be sealed. Any moisture that wicks into the crack between the mount and the stanchion will drain from the crack between the mount and the deck. The chamfer provides a void for the butyl to fill around the bolt threads.

If you're sealing the entire object, such as a window frame or tail light assembly, then the bolt/rivet holes don't require chamfering.


The mounting bolt holes around the perimeter of a Fantastic-Fan have huge chamfers in relation to the size of the heads of the bolts provided. You don't want standing water on top of the bolt head, for even stainless steel will rust under constant contaminated water exposure with enough time allotted. This is why you add caulk, but it is only necessary to cover the chamfered bolt heads.

Good points Fred. The manufacturer of my Bigfoot used what I now understand to be the good butyl tape as a bedding for the roof vents and a topping or caulk (Plas-T-Cote?) over the flange and mounting screws. I now see the wisdom of the butyl tape but the choice of topping is questionable because it is now very hard, brittle and beginning to flake off. I think something that remains flexible would be more appropriate. Perhaps a Dicor lap or self-leveling sealant?

[Frederick L. Simson]

Originally Posted by SRD

Perhaps a Dicor lap or self-leveling sealant?

C-10 Self Leveling Caulk from Dyco

[Carol H]

A question on using the self leveling caulking around a butyl tape installation.

Today working on getting 22 years of caulking off my escape hatch, although most of it looks like it was the original install. Putting the hatch back on using butyl as I did my Fantastic Fan which hasnt leaked here on the Wet coast since install 4 years go and no leveling caulking around it.

Question: Is there a need/advantage to putting leveling caulk around the escape hatch after its been reset with butyl tape? Wondering if I should be using it this time around.

[Frederick L. Simson]

Originally Posted by Carol H

Is there a need/advantage to putting leveling caulk around the escape hatch after its been reset with butyl tape?

It depends; considering your experience with your Fantastic-Fan installation.

IMHO the issue is standing water. If you expect contaminated water to stand on the roof against the butyl seal for long periods, then I would add the Dicor C-10 for a layered defense. Same concept as resin coating the edges of a plywood floor and its through holes to prevent wicked seepage.

[Carol H]

Originally Posted by Frederick L. Simson

It depends; considering your experience with your Fantastic-Fan installation.

IMHO the issue is standing water. If you expect contaminated water to stand on the roof against the butyl seal for long periods, then I would add the Dicor C-10 for a layered defense. Same concept as resin coating the edges of a plywood floor and its through holes to prevent wicked seepage.

Thanks Frederick - having more/extra protection is never a bad thing for the what ifs, which is why I was thinking about adding it. But was wondering about compatibility - any issues/compatibility with leveling type such as Dicor c-10 coming in contact with the small spots of butyl tape around the edge that you know of?

[rabbit]

Carol, I know I wouldn't bother with the bead of lap sealant at the edge is a window flange bedded with butyl tape but I believe Frederick's comment on applying it to the heads of bolts in a horizontal ap like a roof fan or hatch makes sense. Even there I'd be sparing of the stuff to avoid filling the common or Phillips slots of fasteners in case someone needs to redo after another 22 go by.

Thinking a bit about that Bimini top stanchion socket is important. Yes the socket should drain on deck so a butyl gasket around machine bolts alone is correct. I hope no one will apply this method when installing a flanged item which surrounds a central opening such as a fan, vent, vent stack cap, other thru hulls. In all these cases a continuous gasket IS required absolutely without exception.


jack

[Frederick L. Simson]

I have installed my Fantastic Fan using both Butyl tape between horizontal layers and Dycor C-10 covering the perimeter edge plus screw heads. The C-10 bridges the fiberglass/butyl/plastic sandwich, adhering well to the (alcohol clean) fiberglass and plastic and encapsulating the butyl. My Fantastic Fan is installed in a partially depressed area where rain water pools on one side until it all evaporates, and I have had no leaks.

Originally Posted by rabbit

Even there I'd be sparing of the stuff to avoid filling the common or Phillips slots of fasteners in case someone needs to redo after another 22 go by.

I have recently moved my Fantastic-Fan to a new vent hole after removing it from the central vent hole to install my air conditioner. I had to drill the C-10 out of the chamfers and use an awl to dig it out of the screw slots. I considered it the cost of the leak prevention.

[SRD]

I just discovered a third roll of so called butyl tape that I bought from an RV parts supplier and never used. The package is sealed and definitely labeled "butyl tape". It is more sticky and pliable than my other stuff but packaged air tight, which leaves me a little suspicious. Is it real butyl tape or fresh no good stuff that will quickly dry out? Is there a test for butyl rubber? Special smell?

[GMike A]

Originally Posted by Frederick L. Simson

. I had to drill the C-10 out of the chamfers and use an awl to dig it out of the screw slots. I considered it the cost of the leak prevention.

Good thing it wasn't C-4

[Frederick L. Simson]

Originally Posted by GMike A

Good thing it wasn't C-4