Recaulking over old caulk

While washing and waxing my Adventurer yesterday, I noticed the caulk on the vertical surface where the roof meets the front cap has begun to crack on the driver's side. The caulk is about two years old, put on by my previous mechanic, and I was told the average life expectancy of this caulk is about two years, so I guess it's due.

My question is this: is it imperative to remove the old caulk and have a completely clean surface, or since the cracking is presently minimal, can I simply put on an outside patch, filling in the crack? The old caulk is urethane, so there won't be a problem trying to put new caulk over silicone.

The side seals still appear to be holding, as well as the vertical seal on the passenger's side, but the mechanic did the entire job at the same time. I'm wondering if I'm going to need to replace the sealing all the way down the sides in short order. I am now trying to do all the work I can in an attempt to save some money and will need advice on things I have never done before.

Can anyone provide an opinion of which sealant to use? Winnebago recommends Manus-Bond Urethane sealant and I have read many good reviews on this site about Geocel Proflex RV sealant. Has anyone tried both and can give a definitive answer of which is best?

Thanks in advance for your advice.

Scrub it good using a stiff brush and soapy water.  Rinse, let dry.  Remove any loose caulk.  Reapply new correct caulk and your good to go. 

It's 2018 and we are still talking about caulk!  In a time when cars will soon be able to drive themselves and we can reuse first stage rocket boosters, we have to plug up holes with stinky old caulk!

You talk about an unsatisfied market?  About every time someone has a leak it's from the caulk job.

Can't one manufacturer figure out how to make a seamless roof so it becomes a worry free part of the RV?  If you had to maintain your car roof like this there would be outrage!  Can you imagine telling someone they better check their 2 year old Toyota roof for caulk leaks?

Would a thin piece of sheet metal bonded like a car's really cost that much more?

Can't a company design a material that outlasts the current two years?  It doesn't seem like that high of a bar!!

Sorry but this drives me crazy because I am never 100% sure I made it truly leakproof and who can afford the rates of an RV dealer to reapply every two years!!!!  I park my RV a few miles from my house so when it rains I always wondering if I should run over there and see if there is a dribble.

One word-Eternabond

X2 on Eternabond.  Applied it to the sidewall in 2012 and it still looks great.

The caulk itself  should last a lot longer than that, but seams on RVs "work" a lot as the house travels down the highway, gets raised by jacks, expands & contracts in heat, etc. Cracks in the surface are not inherent signs of failure, but it's something to keep an eye on.  As to caulking over old caulk, that is OK as long as the previous layer is not silicone. Silicone must be removed, cause nothing else sticks to it.

KandT: the reason for the caulk is to allow for movement at the joints. The movement is unavoidable at any price you & I could pay for a coach, so a flexible joint is almost a must. Even concrete highways have expansion joints!  A monocoque steel shell such as on the Prevost conversions is probably as close as one can get to perfect joint/seam construction and even those aren't 100% trouble-free.

KandT said:

It's 2018 and we are still talking about caulk!  In a time when cars will soon be able to drive themselves and we can reuse first stage rocket boosters, we have to plug up holes with stinky old caulk!

You talk about an unsatisfied market?  About every time someone has a leak it's from the caulk job.

Can't one manufacturer figure out how to make a seamless roof so it becomes a worry free part of the RV?  If you had to maintain your car roof like this there would be outrage!  Can you imagine telling someone they better check their 2 year old Toyota roof for caulk leaks?

Would a thin piece of sheet metal bonded like a car's really cost that much more?

Can't a company design a material that outlasts the current two years?  It doesn't seem like that high of a bar!!

Sorry but this drives me crazy because I am never 100% sure I made it truly leakproof and who can afford the rates of an RV dealer to reapply every two years!!!!  I park my RV a few miles from my house so when it rains I always wondering if I should run over there and see if there is a dribble.

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Hmm. I'm not sure how to respond to this post, so I'll just say what's on my mind: To bellyache about something that was mentioned in an original post without providing answers to the questions posed is not only as waste of the readers' and OP's time, it is downright rude and socially unacceptable. I didn't ask my questions to start a war or any kind of discussion regarding the necessity of using caulk on a motor home because I thought anyone intelligent enough to answer my post would also be intelligent enough to understand why caulk is a necessity and be able to bypass any negative thoughts on the subject. In the future, please keep your negativity to yourself. And to answer your question regarding why caulk is still being used in 2018, please refer to Gary's answer. I couldn't have said it better and he used a lot more tact.

Gary, thanks for your answer regarding caulking over old caulk. The cracks I am seeing are not surface cracks, but rather, where the caulk has separated from the fiberglass. Since the cracks are relatively clean and not jagged, I think I'll be safe simply patching them for a temporary fix. Then, when I am ready to redo the entire roof seal, I'll clean it thoroughly. It sounds like there is a lot of support for Eternabond. I knew they made the tape, but didn't know they also made a caulk sealant. What is your opinion about it compared to ProFlex or the Manus=Bond that Winnebago recommends?

John Stephens said:

Hmm. I'm not sure how to respond to this post, so I'll just say what's on my mind: To bellyache about something that was mentioned in an original post without providing answers to the questions posed is not only as waste of the readers' and OP's time, it is downright rude and socially unacceptable. I didn't ask my questions to start a war or any kind of discussion regarding the necessity of using caulk on a motor home because I thought anyone intelligent enough to answer my post would also be intelligent enough to understand why caulk is a necessity and be able to bypass any negative thoughts on the subject. In the future, please keep your negativity to yourself. And to answer your question regarding why caulk is still being used in 2018, please refer to Gary's answer. I couldn't have said it better and he used a lot more tact.

Gary, thanks for your answer regarding caulking over old caulk. The cracks I am seeing are not surface cracks, but rather, where the caulk has separated from the fiberglass. Since the cracks are relatively clean and not jagged, I think I'll be safe simply patching them for a temporary fix. Then, when I am ready to redo the entire roof seal, I'll clean it thoroughly. It sounds like there is a lot of support for Eternabond. I knew they made the tape, but didn't know they also made a caulk sealant. What is your opinion about it compared to ProFlex or the Manus=Bond that Winnebago recommends?

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You are right John - my apologies.  No reason to complain and I hadn?t thought about Gary?s point regarding the flexing that needs to be done. 

My comments really were not in the spirit of the forum.  I chose a poor medium to vent on a problem that seems to be a constant headache and one that I never feel confident about the fix. 

I won?t continue to go on but will try to mute myself in the future.

Apology accepted.

John Stephens said:

....Can anyone provide an opinion of which sealant to use? Winnebago recommends Manus-Bond Urethane sealant and I have read many good reviews on this site about Geocel Proflex RV sealant. Has anyone tried both and can give a definitive answer of which is best?..

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I'm almost 100% positive I've used both and I don't recall any performance difference. Where the corners of the cap meet the sidewall, two or three stainless screws can be used to somewhat fix the location of the cap to prevent some flex and sealant separation.

Like others have mentioned, Etrnabond is a good solution as long as there's good surface prep but cosmetics could be an issue. A buddy had a persistent leak problem on his Trek's front cap (where it met the roof) and he finally used Etrnabond.  It came loose after a few years due to inadequate surface prep.

3M has an excellent line of marine sealants, marine applications are very demanding and our 40' ketch in heavy seas would really work - we always heard weird creaking sounds as the hull and deck moved under stress. All deck fittings were bedded in 3M-5200 and we never had leak issues. I also used Boatlife Life Calk with excellent results.

It sounds like there is a lot of support for Eternabond. I knew they made the tape, but didn't know they also made a caulk sealant. What is your opinion about it compared to ProFlex or the Manus=Bond that Winnebago recommends?

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First, I am not of the opinion that Eternabond tape is the answer to every roof question. It's a great product and I use it myself, but a tape is not always the best method of sealing something. Sometimes a caulk (lap sealant) works better, and sometimes a combination of sealant & tape is the best solution. It depends on the size of the gap, the shape of the surface,  flat vs ridges or rough, etc.

I've seen no reports about actual use of the EternaCaulk product, but it claims to be EPDM compatible. Given that it claims to cling to almost any type of surface, it might be a good choice if you can carry only one type of caulk. However, I see nothing in its description about self-leveling or non-sag, so I'm guessing it is fairly typical caulk consistency. That means a slight sag on vertical surfaces.

Geocel Proflex does not claim EPDM compatibility, though I've not heard of any actual problems using it over EPDM. I like the Proflex as  a general use caulk, though. I haven't owned anything with an EPDM roof since 2001, so I use Proflex extensively myself.

Manus is basically an industrial sealant manufacturer, meaning their products are sold primarily to factories and not widely available at retail. I don't know which of the dozens of Manus products you (or Winnebago) is referring to, but it's probably a good one. Factories choose caulks for other reasons in addition to sealing performance. They use industrial size/grade power guns and gallons of caulk everyday, so their production-use concerns are as important as the sealing qualities.

I think that's "What's best?" is largely an academic discussion. This is a mature technology and application and most any suitable type of product ought to work very well.  It should be EPDM compatible if that's the surface where it will be applied. You want self-leveling for horizontal flat seams and non-sag for most others. You want excellent elongation (stretchiness) over a broad temperature range, say 10-160 F. Good caulks stretch more than 100% and some are much more.  The commonly used retail brands, e.g. Dicor's lap sealant, work so well that discussing which is better is all but pointless.

The cracks I am seeing are not surface cracks, but rather, where the caulk has separated from the fiberglass.

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Sounds like either poor prep work or some really serious movement at that joint. Caulk should not separate from the surface of its own accord if the surface was clean and dry, but repeated extreme stretching can pull it loose.

Eternabond tape is an excellent product for roofs where a repair is required and around roof structures but I would be reluctant to apply it to the point where the roof meets the sides, front cap and rear wall.  Mostly because while Eternabond is a very good product and when applied as directed, works well, IMHO it is not all that attractive, not a concern on the roof, but on the corners where it can be seen from the ground will detract from the rigs appearance.  I would just rather patch caulk or re-caulk as necessary for those areas.  In addition, I can imagine it would affect resale and may be a hard sell to a potential buyer that the Eternabond taping was done as a preventative measure and not because of a problem.

Gizmo said:

Eternabond tape is an excellent product for roofs where a repair is required and around roof structures but I would be reluctant to apply it to the point where the roof meets the sides, front cap and rear wall.  Mostly because while Eternabond is a very good product and when applied as directed, works well, IMHO it is not all that attractive, not a concern on the roof, but on the corners where it can be seen from the ground will detract from the rigs appearance.  I would just rather patch caulk or re-caulk as necessary for those areas.  In addition, I can imagine it would affect resale and may be a hard sell to a potential buyer that the Eternabond taping was done as a preventative measure and not because of a problem.

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X2
I've even seen it yellow on a repair my buddy did.  It's kind of like RV duct tape - the last resort when the factory technique didn't work or you just needed to get on the road.

Gizmo said:

Eternabond tape is an excellent product for roofs where a repair is required and around roof structures but I would be reluctant to apply it to the point where the roof meets the sides, front cap and rear wall.  ..

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For the older Winnebago roof to sidewall radius (a particular extrusion used for many years), Etrnabond works quite well and solves the never-ending requirement to inspect that roof to sidewall joint at least once a year for sealant adhesion. The two reasons why I haven't done this is, a) it's a lot of work and b) cosmetics would be an issue.

I have a small gap on the right rear where the cap corner meets the end of the sidewall and any kind of sealant I've tried always become separated after a few months apparently due to a focus of sidewall-roof-rear cap stresses and movement. As a test, I tried WEST System epoxy with an appropriate filler in that void and as expected, the bond broke. Next I need to saturate some fiberglass mat and try again.

Gary RV_Wizard said:

Sounds like either poor prep work or some really serious movement at that joint. Caulk should not separate from the surface of its own accord if the surface was clean and dry, but repeated extreme stretching can pull it loose.

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Gary - I thought the same thing but knew my mechanic had done a decent job two years ago. It dawned on me, though, that while escaping the hurricane, we stayed in a rest area that was so off level, it torqued the coach to the point that one of the slides wouldn't slide all the way out and the door wouldn't close and lock properly. I didn't realize what was causing these problems until we put the leveling jacks back into travel position. Then, the slide and door both worked properly, telling me I had a twist problem. That twist may have caused the caulk joints to crack and separate from the body. Since I hadn't seen those cracks the last time I inspected the caulk prior to our vacation just before the hurricane, I have to believe the problem I had in that rest area caused this issue.

If you are going to be way off level and the jacks only can partially compensate, retract them and don't use. We had a situation like that many years ago and we extended the slides with no jacks - worked great on a temporary basis.

John - Lesson learned. Had I known the off level situation was that bad, I would have moved to a different spot in the rest area. My primary concern was keeping the fridge level since all of the frozen and refrigerated food from our house was in there. When the problems were found, we assumed the slide was simply something else wrong with the coach after our vacation. The door, however, puzzled me. Since it had become loose due to bad road the year before, I thought possibly the lock washers I installed on the hinge screws didn't do their job. But when I tried to tighten the screws more, they wouldn't budge, so I was pretty sure the door hadn't slipped out of position again. It wasn't until we were ready to leave the next day that I realized the door was once again working correctly. I didn't try the slide until we got home, not wanting to get it stuck halfway out and then having to drive back home. When both it and the door worked again, I put two and two together. Until then, I never thought the torque on the frame and body was that severe.

John Stephens said:

John - Lesson learned. Had I known the off level situation was that bad, I would have moved to a different spot in the rest area. My primary concern was keeping the fridge level since all of the frozen and refrigerated food from our house was in there. ....

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It took us a few years and thousands of miles to get through the initial learning curve with the coach and RVing in general (and we still get surprised once in a while  .) When you mentioned the fridge issue being off-level, that's yet another reason to change to a residential model - it doesn't care.

http://rvroof.com/