Over cab leak. Newb.

[Tta]

Hey. Just got a new to me 2012 28a thor majestic… bad front cab over leak. I am looking to find the source but the base was soaked, walls soaked. Drivers front corner seems to be the worst at the bottom for mould. Front interior panel and ceiling panels yet to be removed but it is wet up to the central top vent, and worse in the drivers front corner ceiling. It is all coming out.

I see a few bad signs… even for a newb like me. Mainly what appears to be silicone calking up on the top roof seam (subsequently done over in places by self levelling sealant… that appears done by someone half blind. I also see overall bad sealing maintenance. From the inside, cab overhang aside, it looks dry.

I am assuming this is not a modern one piece fiberglass cab over. With water on the ceiling, any thoughts on the typical leak source? It does not appear to be the top air vent itself. My thought is a roof seam near the drivers front corner.

Plan to get a pro opinion, but also looking to get some dico self levelling caulking, and non sag respective. I will get it all resealed or at a minimum reseal it myself. And the front is getting a full interior teardown and replace.

Any tips on materials appreciated. I was thinking of keeping it simple and water proof… like high density styrafoam, plywood, then vinyl fooring on top for the floor. Possibly in removable sections for easy leak management and diagnosis.

Less sure on the walls, especially the ceiling and around the side windows. But i am looking to gut it and start over. It appears to be a wood /styrofoam sandwich that is glued onto the fiberglass itself… but i have yet to get beyond what i think is the final laminate of wood that i presume is adhered directly to the fibreglass.

Any thoughts and wisdom would be appreciated.

[Tta]

Also, any thoughts on a good cover. Will be needed asap until i get this sorted in early may.

[Judge]

Getting a couple large blue tarps somewhere might be the cheapest and easiest way to stop the leaking until you can get to it.


You are correct..... it is not a one-piece cap. There are plenty of places for it to leak.

- The running lights in the cap
- The molding around the sides of the cap
- The windows in the cap
- The attachment point at the cap and the roof

You will have to gut it. Based on the leaks you are seeing I'm betting there will be a lot of damage once you peel back that onion.

I've never done a job that large before but I do have one recommendation. Once you get it back together, use EternaBond Tape over every joint, seam and opening in the roof.

My last two coaches, I cleaned the roof and then used Eternabond Tape (rolls of varying width) to cover the Dicor and overlap the roof and cap surfaces. Never had any leaks and no more roof maintenance other than cleaning once a year.

[Tta]

Originally Posted by Judge

Getting a couple large blue tarps somewhere might be the cheapest and easiest way to stop the leaking until you can get to it.


You are correct..... it is not a one-piece cap. There are plenty of places for it to leak.

- The running lights in the cap
- The molding around the sides of the cap
- The windows in the cap
- The attachment point at the cap and the roof

You will have to gut it. Based on the leaks you are seeing I'm betting there will be a lot of damage once you peel back that onion.

I've never done a job that large before but I do have one recommendation. Once you get it back together, use EternaBond Tape over every joint, seam and opening in the roof.

My last two coaches, I cleaned the roof and then used Eternabond Tape (rolls of varying width) to cover the Dicor and overlap the roof and cap surfaces. Never had any leaks and no more roof maintenance other than cleaning once a year.

Yeah, sadly i think you are right about the tip of the iceburg. I saw no other visible signs of water leak in any other area, but what i learned is that it can be water-logged and the vinyl will hide it. What looked like one corner area was far worse once i peeled it back.

Are there moisture probes that can be inserted in the walls?

[Judge]

There are thermal imaging cameras like this one that can help detect water damage as well as other problems.....

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[Tta]

Originally Posted by Judge

There are thermal imaging cameras like this one that can help detect water damage as well as other problems.....

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Yeah i will get a sensor in my hardware store. I will see what options they have and cross my fingers that only the front is a problem. I can deal with that. More… uugh.

[JimOIB]

Judge’s first post are the exact 4 places I had water leaks on my class C. I have a few posts on the site as to my trials and tribulations over 18 months and here are the cliff notes. BTW I just rebuilt my cabover and it wasn’t fun.

Roof/cap seam - screws worked themselves out and caused the lap sealant to bubble and crack. I removed all of the lap sealant, replaced the corroded screws and resealed with lap sealant. Inspect every six months and patch as needed. Point of where I noticed water coming into the cab was the ceiling T molding over the cab window.

Running lights - sealed with ProFlex RV.

Edge trim around the cab - major source of water leak. The trim actually moved when I pushed it. I took out the vinyl insert trim and found all of the screws rusted (I have a post on this). There wasn’t any butyl tape to cover the seams along the trim. Plus the screws were too short to get a good bite on the mating parts. New butyl tape, longer stainless screws and sealed all the edges with ProFlex RV.

Window - the bead of factory sealant was only making about 20% contact with the cab wall. I could see the water running in with a heavy ran (I have a post showing this). I used the Dicor Seal-Tite reseal kit to reinstall the window.

Then every outside penetration on the coach got a bead to ProFlex RV around it.

Some more bad news - the edge trim leaks weren’t limited to the cab. The wing walls started to rot along the seam where they meet the main sidewalls. I took the inside padded walls off and saw nothing but rot. I had to carefully cut out the wood down to the fiberglass and refill with fiberglass filler.

After all of this the damage was done and I gutted the cabover except the ceiling - I caught the leak there early enough. I took out all the OEM stuff and threw it in the trash - storage areas, bed, everything. Then I took up the cabover floor. It is 1/4 luan glued to a matrix of square aluminum tubing, aluminum straps between the tubing and rigid foam insulation. A nightmare to get up. I found a vibrating multi tool, 6 in putty knife and a 5 in 1 painters tool combination worked. Once everything was out I sprayed with mold/mildew cleaner and repeated for 3 days. Finally the smell was gone.

Word of caution - when working in the cabover with the floor up put down a piece of plywood spanning the alum tubing to kneel on other wise you will go through the bottom of the cab.

If you want to see how I rebuilt the cabover let me know and I’ll send you some details.

I would send some pictures of all of the above but I’m on the road with limited connectivity. Look for my posts - they have pictures.

Jim

[Tta]

Originally Posted by jimbo12

Judge’s first post are the exact 4 places I had water leaks on my class C. I have a few posts on the site as to my trials and tribulations over 18 months and here are the cliff notes. BTW I just rebuilt my cabover and it wasn’t fun.

Roof/cap seam - screws worked themselves out and caused the lap sealant to bubble and crack. I removed all of the lap sealant, replaced the corroded screws and resealed with lap sealant. Inspect every six months and patch as needed. Point of where I noticed water coming into the cab was the ceiling T molding over the cab window.

Running lights - sealed with ProFlex RV.

Edge trim around the cab - major source of water leak. The trim actually moved when I pushed it. I took out the vinyl insert trim and found all of the screws rusted (I have a post on this). There wasn’t any butyl tape to cover the seams along the trim. Plus the screws were too short to get a good bite on the mating parts. New butyl tape, longer stainless screws and sealed all the edges with ProFlex RV.

Window - the bead of factory sealant was only making about 20% contact with the cab wall. I could see the water running in with a heavy ran (I have a post showing this). I used the Dicor Seal-Tite reseal kit to reinstall the window.

Then every outside penetration on the coach got a bead to ProFlex RV around it.

Some more bad news - the edge trim leaks weren’t limited to the cab. The wing walls started to rot along the seam where they meet the main sidewalls. I took the inside padded walls off and saw nothing but rot. I had to carefully cut out the wood down to the fiberglass and refill with fiberglass filler.

After all of this the damage was done and I gutted the cabover except the ceiling - I caught the leak there early enough. I took out all the OEM stuff and threw it in the trash - storage areas, bed, everything. Then I took up the cabover floor. It is 1/4 luan glued to a matrix of square aluminum tubing, aluminum straps between the tubing and rigid foam insulation. A nightmare to get up. I found a vibrating multi tool, 6 in putty knife and a 5 in 1 painters tool combination worked. Once everything was out I sprayed with mold/mildew cleaner and repeated for 3 days. Finally the smell was gone.

Word of caution - when working in the cabover with the floor up put down a piece of plywood spanning the alum tubing to kneel on other wise you will go through the bottom of the cab.

If you want to see how I rebuilt the cabover let me know and I’ll send you some details.

I would send some pictures of all of the above but I’m on the road with limited connectivity. Look for my posts - they have pictures.

Jim

Well the vendor is rebuilding that cab. Front off deal. And the rear… that will come off too as i detected moisture in the back wall and ceiling of the bedroom (bonus… middle of the rv is dry… lol).

I found the source of the rear leaks… two big fresh cracks. One on each top rear corner of the rv… right next to the metal seams. They looked somewhat fresh and had never been re- calked since leaving the factory.

So i did some quick calking of overtly problematic areas on the top and it will go in dry storage for work. Lots of rain this week.

One thing i noticed it that i presume the rear 2/3rds of the edpm roof is original… and maybe the front was at one time replaced. I say this because the rear has lichen growing in spots (could be shaded also)… and… it sounds “crunchy” to walk on. This makes me think that the laminated wood underneath was wet and is now dry and warped. Thoughts? Looks good from inside.

On a positive… recalking is satisfying. I am scraping, then using alcohol to clean (isopropyl) then calking. I am new to rv’s but i have already done a far better job than any prior owner… who seemed to gob on tons of self levelling calk with their eyes half closed. However, i still think to myself that prep is key… and can i do more to prep?

[Judge]

Originally Posted by Tta

.

On a positive… recalking is satisfying. I am scraping, then using alcohol to clean (isopropyl) then calking. I am new to rv’s but i have already done a far better job than any prior owner… who seemed to gob on tons of self levelling calk with their eyes half closed. However, i still think to myself that prep is key… and can i do more to prep?

Personally.... after you go through and deal with cleaning out the old Dicor and reapplying new Dicor, I would apply EternaBond tape over all of it overlapping the Dicor... the roof... and the front and rear cap seams. You will never have to maintain the roof by applying Dicor ever again..... and it will never leak of done right!

[Tta]

Originally Posted by Judge

Personally.... after you go through and deal with cleaning out the old Dicor and reapplying new Dicor, I would apply EternaBond tape over all of it overlapping the Dicor... the roof... and the front and rear cap seams. You will never have to maintain the roof by applying Dicor ever again..... and it will never leak of done right!

Yeah that was the plan. Though removing all old dicor would be a job. My only hesitation was what could not be seen. But i guess i would just need to inspect the tape for stretch.

Is tape over a edpm roof ok? I will probably clean and coat my roof also.

[Judge]

Originally Posted by Tta

Yeah that was the plan. Though removing all old dicor would be a job. My only hesitation was what could not be seen. But i guess i would just need to inspect the tape for stretch.

Is tape over a edpm roof ok? I will probably clean and coat my roof also.

Yes...... Eternabond tape over an EDPM or TPO roof is ok.

But you are correct.... you need to remove all then old Dicor and inspect screws, wood, etc. You are going to need to fix what's bad first and then get her good and sealed.

[JimOIB]

If the roof is as bad as you say and the wood under the EPDM is “crunchy” then I would rent some covered storage and replace the complete EPDM membrane and repair any wood under it that is bad. Once the wood gets crunchy it will continue to dry rot and one day you will step and go through the roof. Plenty of videos online on how to do this. IMHO patching up “bad” is a temporary fix and not a long term solution. You have a summer project now.

[Tta]

Originally Posted by jimbo12

If the roof is as bad as you say and the wood under the EPDM is “crunchy” then I would rent some covered storage and replace the complete EPDM membrane and repair any wood under it that is bad. Once the wood gets crunchy it will continue to dry rot and one day you will step and go through the roof. Plenty of videos online on how to do this. IMHO patching up “bad” is a temporary fix and not a long term solution. You have a summer project now.

Summer project? You mean money pit?

[alajeu]

Don't mean to be snarky but the only way to recover from your problem is to blow it up. I had a over the cab design C Class that fell apart while driving down Hwy 55 in Miss. The siding was flopping in the wind. Had to stop at a truck stop and buy some duct tape to use to hold everything together on the way home. The repair job was quoted at $8,000. I was told that it was only a matter of when, not if, such a thing would happen.



Alajeu

[dfougere]

I had the same issue with a Majestic that Ipurchased used from Cruise America. The problem is the seam that transitions the EPDM roof to the front fiber glass cowling. I removed the EPDM to about 6 Feet back and removed the under roof of plywood that was soft and delaminating. I then replaced the under layment (plywood) and proceeded to replace that portion of the EPDM that I had removed with a new piece of EPDM I sealed the juncture of the new EPDM with the remaining EPDM with 4 inch EPDM tape ( this tape comes in various widths but I chose to be cautious and used 4 inch. Then I overlapped the front section over the fiber glass cowling and secured it with a strip of metal screwed into the fiberglass. I then covered the whole joint with the 4 inch epdm tape sticking to the fiberglass on one side and the EPDM roof on the other completely covering the metal band. I hope this helps, if you want to contact me directly send a messaage thru this site.

[Tta]

Well… a bit of an update on this… hot mess.

Using a dual probe water sensor there is dampness mid section around the shower. Most of the back wall is internally wet. Some vinyl delamination. There is delamination of the fiberglass in the drivers side rear bottom corner (above the bumper). The wall and outer half of the roof by the toilet stall has been wet, and is wet. The rear bedroom wall on the drivers side is wet. The front overhang needs a full rebuild, we know. Dampness does not go beyond the drivers cab region on the drivers side…

So the front is bad, the back bedroom is going bad in the drivers side rear corner, and much of the bedroom and toilet/shower region is wet. It all appears to be poor sealing of the roof membrane (poor maintenance). Maybe a roof vent or two. The back 2/3rds of the roof is crunchy.

The complication that is see is that it is a glued fiberglass/wood/styrofoam/wood/vinyl walls setup. I.e. a moisture trap with no easy access.

Are we looking at ripping it open from the inside and gutting it to dry it out? I know we can peel back the roof… and that is next. Am i right in assuming nothing will dry outside a few inches form exposed seems unless the vinyl is off? What about behind the styrofoam? Is vinyl off good enough. The issue as i see it is possible current or pending rot of the wood skeleton what the screws anchor into. Accessing those in the corners of the frame in the bedroom would require an internal teardown.

Is this as bad as i am imaging? Simply because the only way to open the walls it to destroy them? How about cutting access panels? The issue is everything is glued…

I know i am screwed. Be gentle.

Or is it just a matter of opening the top and letting the dry fairies do their magic?

[Redsand]

I can only imagine what you're going through. We bought our 2005 Thor last Oct and we're finally to the point of being able to use it. By comparison our water damage was minimal with a 2 x4 foot area of roof water damage. I had to do a new shower skylight and luan panel. Youtube has a wealth of info on what is required to do a professional repair. Material was inexpensive compared to labor so I did all the work myself. Not easy but rewarding. Try a search for rvexpert on youtube. You've got a pretty big project ahead for sure.
There's lots of experts here as well to help you along the way..

[Pillbox]

X2 on az rv expert, James is the man.
Terry

[Tta]

Well that ended the best way possible. Total refund. I have no stomach or time for a money/labour pit.

Some battles are best not fought.

[Judge]

Originally Posted by Tta

Well that ended the best way possible. Total refund. I have no stomach or time for a money/labour pit.

Some battles are best not fought.

Wow..... you got lucky! I think you made the right decision given the train wreck you uncovered.