A graphic example of caulking "rot"

**JRTJH** · 07-06-2017, 11:40 AM

I am in the process of installing slide covers on our fifth wheel. To do so, I have to relocate the gutters that Keystone installed over the slides. When I removed the first one I discovered that Keystone used "clay caulk tape" to install it and ran a bead of SikaFlex along the top edge of the molding. That is the typical way Keystone installs almost all the aluminum moldings on every trailer.

These pictures show the dry rot/drying and cracking or whatever you want to call it that has occurred to the clay putty tape. Our trailer is a 2014, this is its fourth summer. Many of us have "ignored" or "avoided" resealing the top edge of the aluminum moldings and have thought that the butyl putty tape under the molding will protect against any water intrusion.

Well, these pictures will show how the cracks in the clay putty will actually 'guide" the water to the screw threads if the SikaFlex bead along the top edge of the molding strip fails.

Consider that along the top of each of our trailers is an aluminum strip that is the "only line of defense" against water intrusion between the TPO/EPDM membrane and the FILON walls.

I'd urge everyone to consider checking their trailer aluminum molding strips to be sure they "really are sealed"... The alternative is discovering significant water damage in a couple of years.......

jsmith948 · 07-07-2017, 05:23 AM

Good info. The ladder on our Cougar (1/2 ton series built in Pendleton) was mounted using what I believe was clay caulk. The caulking had shown signs of crumbling where it had "extruded" around the mounting brackets. Replaced with butyl tape. Recently had occasion to remove the furnace vent - it had been sealed with butyl tape and then a bead of clear sealant that looks and behaves like silicone. It seems that all of the trim, gutters and roof edges are sealed with this same "silicone appearing" sealant. I wonder if this is the Sik-a-flex" that you are referring to?
I recently bought some "ProFlex" clear sealant and it was very difficult to use. The sealant may have been beyond its shelf life because it was very viscous and did not tool well at all. I want to try the Sik-a-flex. Can this sealant be applied over the old sealant like the Dicor or does one need to remove the old sealant (no small job)?
Thanks in advance for any and all help - got to love this forum

**JRTJH** · 07-07-2017, 06:05 AM

The following is my opinion based on my experiences with ProFlex, SikaFlex and Silicone sealants that are applied from a "caulking gun tube"....

ProFlex is a very thick "paste" that doesn't sag, is great "IF" you're an expert at applying a smooth, straight bead of sealant. It doesn't tool well and will adhere to itself, to other types of "NON-SILICONE" sealants and will adhere to wet oily surfaces as well as dry, clean surfaces. It sets up "harder than silicone" and is almost impossible to remove once it's set.

SikaFlex is a medium thickness "paste" that doesn't sag, is easier than ProFlex to tool. It will adhere to itself but will not adhere to wet or oily surfaces. It will adhere to "NON-SILICONE" sealants such as ProFlex. It sets up faster than ProFlex, usually in less than 20 minutes and if wiped before it sets up, it smears and is impossible to remove. So, apply it carefully, use masking tape if you're a "messy applicator" and remove the masking tape as soon as you smooth the surface. Otherwise, the tape will become a part of your trailer.

Silicone is a medium thickness "paste" that doesn't sag, easy to apply, easy to tool, can be cleaned up before it sets with many solvents. Once it sets up, it can only be removed mechanically (scraping/peeling) and from my experience, NOTHING sticks to it once it's set. So, it's easy to use, easy to tool, difficult to remove and hard to get anything to stick where it was. It doesn't seem to last as long as ProFlex or SikaFlex.

My personal preference is SikaFlex. If I'm applying it where I need a smooth, visible line of sealant, I use masking tape, apply the SikaFlex, tool it smooth with my finger and then carefully pull the tape away before it sets up. Since it sets so rapidly, I do a small area at a time, maybe 3 or 4 feet of bead. For doing the roof aluminum moldings, I don't worry about appearance, just clean the old sealant, remove any damaged sealant and apply an overlapping bead that covers the old and overlaps the sides of the old sealant.

SikaFlex is about double the price of ProFlex and about 3 times more expensive than HD or Lowe's silicone, but even at $12 for a tube of SikaFlex it's "cheap" considering it's a "once a year expense" and one tube will do almost any trailer. My recommendation is to prepare the entire trailer before you ever cut the tube and start using it. Once it's open, the longer it sits in the tube, the harder it is to apply. I've tried to save it by sealing the tube, freezing it, etc. Nothing seems to preserve the un-used SikaFlex, once the tube is opened, it's good for a day or two, then it gets extremely hard to push out of the tube.

jsmith948 · 07-07-2017, 07:40 AM

John - Thanks for the response and the detailed info. I think I will try some Sikaflex on a spot where the sealant is still good - maybe along the lower trim of the rear wall where it won't show - to test if it will, after being carefully cleaned, adhere to the existing sealant. If it does, then I'm okay. If it won't adhere then the existing sealant is silicone. I can't imagine the factory would use silicone given the fact repairs would be so much more difficult (having to remove the old sealant to apply new). But it seems the Oregon plant sometimes marches to a different drummer. I might try contacting the Pendleton plant - maybe they can confirm which sealant is used.
Thanks again for the valuable insight.

dcg9381 · 07-14-2017, 11:33 AM

thank you.

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