Exterior caulking and maintenance

[Bulgmaf]

During a self-inspection, I recently noticed hardening and micro-cracking in the small beads of caulk used on all of the exterior trim joints of our 2017 Summit. We’ve been on the road for about a year, so time to do some annual maintenance work.

Does anyone know what type of exterior sealer product NH uses in these trim areas at the plant when they do a build?

Is it normal to have to re-seal these areas only after one year?

What product should I use to re-seal - silicone or non-silicone? (Internet opinions vary widely on the whole silicone vs. non-silicone issue - how do you know who’s right?)

Do I need to clean out all of the old material first or can I apply new over the top, since these are pretty small cracks and the factory bead is still fairly well-adhered?

[Murphcrud]

It sounds like the vehicle was moved before the sealant had a chance to fully cure, which will cause it to craze or checking, on the surface. There is no need to repair or remove the sealant, as from your description, the seal is still intact. Regarding applying sealant over the existing sealant, that is not recommended or needed.
I have been selling silicone for almost 50 years, and can assure you, the sealant on your RV is not silicone. The manufacturers do not use silicone for this application, mainly due to the cost. The probable product on your RV is a thermoplast sealant similar to Dicor. They use this product as it has the properties required to absorb movement as it remains flexible while exhibiting excellent adhesion to most substrates from vinyl to glass to steel to wood to aluminum to stone to concrete ---- I think that you get the message. lol. Regular silicone will not bond permanently to vinyl, stone or concrete.
Uncured silicone and uncured dicor (thermoplast) are NON compatible. If you use silicone over cured dicor, the silicone will bond to the cured dicor. I share this information so that you will not be afraid to silicone for some application on your RV.
Dicor is much more abrasive resistant than silicone, when fully cured. Full cure time is usually 7 days for a bead thickness of 1/8". Of course, the bead thickness of the sealant is a major contributor of cure time at ambient temperature.

[shill]

Murphcrud......I hope your response helps the OP. Not sure what you do for a living but I thank you for the lesson regarding sealant properties. I learned alot.


Skip

[CountryB]

How do you feel about the Silkaflex 221 and/or 3M 5200 that others recommend?

[geo-gypsy]

The sealant used by NH and most all other RV manufacturers and the better repair shops is Geocel MHRV 2300. You can get it from Amazon, but it requires a slower method of shopping due to the aromatic hydrocarbons in its fluid state.

Just my two cents,

Ron

[Murphcrud]

Originally Posted by CountryB

How do you feel about the Silkaflex 221 and/or 3M 5200 that others recommend?

Sikaflex 221, 3M 5200 and Geocel MHRV 2300 are all moisture curing polyurethane sealants --- all are very good sealants. I have listed them in order (in my opinion) as Excellent, Very Good and Good. All will serve their intended purpose for most applications. Please note, Geocel MHRV 2300 is NOT for use in potable water applications. Sikaflex has higher solid contents that either of the 2 mentioned sealants, which which contributes to higher tensile strengths. Shrinkage of sealants with higher solvent contents as Geocel, puts a strain on the bond line when solvents evaporate during cure. All are priced higher than thermoplast sealants, which do not necessarily make them any better for some applications. The key to using any of these higher end products is to clean the substrate that you are applying them to -- and after you clean it, clean it again and don't fall for the 'ah, that's good enough' theory. Do it the right way and do it only once - I am a strong believer in this. Why do some RV manufacturers use Geocel? Price is the major factor with choosing it, but at the same time, it still must do the job.
As a few added tips for users of these four products (including thermoplast sealants), it is also important to insure that 100% wetting of the sealed area is critical to insure a good bond. Wetting is the method of smoothing out the caulked joint. You all have seen guys stick their finger in their mouth or water and smooth the caulked areas. This is called 'wetting' the sealant. Some applicators use a tongue depressor or popsicle stick to smooth the sealant. If the sealant is merely gunned out onto the joint, it may or may not have 100% contact with the intended area.
The last tip, AFTER you have applied and tooled the sealant, you can use water in a mister, to speed up cure time of these sealants as all are 'moisture cure' products. The mister method, also allows the sealant to skin over quicker to prevent dust from settling onto the applied sealant.

One reader asked where I have gathered all of my knowledge - I have been around sealants, both our own and competitors, for close to 50 years. Now that I am retired, it is like money, "you can't take it with you", so why share it --- not the money, just the knowledge

[Prof_Lube]

I'm so glad you're offering your expertise on this. Most of the sealant threads are regarding roofs. One thread that i followed for a bit had recommended Silkflex 1A. would you care to weigh in on this one?

Originally Posted by Murphcrud

Sikaflex 221, 3M 5200 and Geocel MHRV 2300 are all moisture curing polyurethane sealants --- all are very good sealants. I have listed them in order (in my opinion) as Excellent, Very Good and Good. All will serve their intended purpose for most applications. Please note, Geocel MHRV 2300 is NOT for use in potable water applications. Sikaflex has higher solid contents that either of the 2 mentioned sealants, which which contributes to higher tensile strengths. Shrinkage of sealants with higher solvent contents as Geocel, puts a strain on the bond line when solvents evaporate during cure. All are priced higher than thermoplast sealants, which do not necessarily make them any better for some applications. The key to using any of these higher end products is to clean the substrate that you are applying them to -- and after you clean it, clean it again and don't fall for the 'ah, that's good enough' theory. Do it the right way and do it only once - I am a strong believer in this. Why do some RV manufacturers use Geocel? Price is the major factor with choosing it, but at the same time, it still must do the job.
As a few added tips for users of these four products (including thermoplast sealants), it is also important to insure that 100% wetting of the sealed area is critical to insure a good bond. Wetting is the method of smoothing out the caulked joint. You all have seen guys stick their finger in their mouth or water and smooth the caulked areas. This is called 'wetting' the sealant. Some applicators use a tongue depressor or popsicle stick to smooth the sealant. If the sealant is merely gunned out onto the joint, it may or may not have 100% contact with the intended area.
The last tip, AFTER you have applied and tooled the sealant, you can use water in a mister, to speed up cure time of these sealants as all are 'moisture cure' products. The mister method, also allows the sealant to skin over quicker to prevent dust from settling onto the applied sealant.

One reader asked where I have gathered all of my knowledge - I have been around sealants, both our own and competitors, for close to 50 years. Now that I am retired, it is like money, "you can't take it with you", so why share it --- not the money, just the knowledge

[ExcitedToRv]

We use Geocel Pro Flex Crystal Clear RV Flexible Sealant on the painted areas (i.e., sides) of our New Horizons. We have been happy with the product. From the numerous New Horizon owners that use the product, I have only received positive comments. It is harder to remove (removing damaged caulk prior to recaulking) than silicone products, but it seals better/lasts longer than silicone per friends that have used both on their New Horizons.

[rollondown]

MurphCrud-
Where does Lexel fall into the category? https://www.lowes.com/pd/Lexel-10-5-...hoCu5YQAvD_BwE

[Murphcrud]

[QUOTE= but it seals better/lasts longer than silicone per friends that have used both on their New Horizons.[/QUOTE]

As we previously mentioned in another thread, silicone is not an 'end all' product like some people think it is. The truth of the matter is that some manufacturer's will tell you that their silicone will last up to 50 years. THIS IS TRUE !! When I first started out in the glass business at a very tender age, I made my Mother a 30" tall plant stand out of 4 pieces of glass using silicone to 'glue ' it together. The round top is 20" round and the legs were fabricated using three pieces of glass. That plant stand is now in the possession of my 53 year old niece, with the glass and original silicone still intact. New Horizons uses Geocel for their laps seems and joints. If we owned one of their RVs, I would probably use Geocel if I had to recaulk a failed joint or seem, myself.
Using silicone verses geocel or other sealant, for various applications, is a matter of choice. geocel or other polyurethanes can be used to seal vinyl, silicone is not recommended for vinyl or plastic. I can assure you, if NH uses geocel, there are probably numerous reasons to do so. First and foremost - will it do the job? yes it will. Of course, the second reason to use this product vs a higher end polyurethane, is cost. But why did the sealant fail in the first place? Did it just lose adhesion? Cleaning or application techniques are suspect. Did it fail cohesively? Usually caused by movement of the joint, beyond the capacity of the sealant. A contributing factor is poor joint design. Geocel contains a high amount of solvents, which flash off during cure which causes shrinkage and stress on the sealed bond line of the joint. Not so with silicone. No shrinkage, no stress of the silicone. We must realize that these manufacturers use an "all purpose" sealant to seal many different applications in your RV as we must realize that this is a production line and the sealant is only as good as the applicator. Where most failures of the sealant occur, are in areas that are not mechanically fastened by use of rivets or screws. This is the area where the sealant is doing it's hardest work.
If all of the joints were created correctly to allow for the sealant to do it's job, there would not be a need to do most of the recaulking work that is being done.
So your comment about friends using both silicone and geocel is a question that only they can answer - Using one on the top of the other? NOT RECOMMENDED. Inadequate cleaning? PROBABLY. We all do that (the old "Good Enough" theory. Poor application? POSSIBLY. Most inexperienced users do not tool the sealant after applying. Tooling is a matter of smoothing the sealant in place to 'wet' the entire joint (usually done with a wet finger or tongue despresser). Are you using the correct sealant for the application? SOMETIMES. If you can find out what was originally used on your RV, either use that again or use a better quality similar product.
IMPORTANT, IMPORTANT, IMPORTANT.
Do not use another sealant or caulk over silicone --- nothing sticks to silicone, except silicone. Even a remaining trace or film after cleaning, will eventually cause loss of adhesion to the new sealant.
Silicone has many uses, just be sure you know what they are.
I hope that I have clarified your comment and educated other readers on this subject.

I could do an Q & A on this subject that would probably last as long as silicone does, but this will have to be "Good Enough" for now.

Take care

[dadej]

Is it normal for a 2014 NH to need recaulking already?

[ExcitedToRv]

Caulk should be checked at least yearly, some say every six months. The point is not to redo (remove, clean, replace) all caulk every year but to touch up and/or replace caulk as needed. It is also important to make sure all relevant areas were sealed to begin with. So in short if, to answer the question about a 2014 (or a 2017) ... yes, the caulk needs to be checked and repaired/replaced as needed.

[ExcitedToRv]

Caulk should be checked at least yearly, some say every six months. The point is not to redo (remove, clean, replace) all caulk every year but to touch up and/or replace caulk as needed. It is also important to make sure all relevant areas were sealed to begin with. So in short, to answer the question about a 2014 (or a 2017) ... yes, the caulk needs to be checked and repaired/replaced as needed (on sides, roof and slide tops).

[Murphcrud]

Totally agree with Excited. It doesn't cost anything to check, but it may cost a lot if you don't.