Hi Brian,
I watched your latest videos. You are doing great! I see you already have the Kreg Pocket Hole jig. They come in real handy in these repairs.
I'll add some details for sealing up the corner moldings, window frames, door frames, or anything that mounts onto the corrugated aluminum siding. You are seeing what happened many years ago now, and it looks so bad that the whole thing rotted out. It took time for that to happen, and it may be hard to see how it ever started. Here is a top-line sequence of events that outlines how this all unfolds.
There are a "lot" of items that mount to the siding. The siding by itself is good for preventing leaks, but then comes the but... any time a screw or a hole is cut into the siding, that seal to the siding is where the leaks originate. The old putty tape shrinks over time, then fine cracks form, then comes "seeper leaks" as I call it. The seeping water wicks into the wall cavities and then down by gravity, until it hits the bottom of the camper, infecting any wood it touches. And the bottom ends up being wet longer as water from above keeps rewetting it. As water pools, corrosion in the siding can start, and after enough time, corrosion pits and holes can develop in the siding or the bottom. Water can seep out of the holes, but when towing in wet conditions, it can also come in, especially on the front wall. Everything at the bottom of the camper gets more water and rots further, and it all accumulates there.
Here are a few pics to see the early stages, where you can see the leak path. This is a 2004 camper, which is a lot newer than yours. The build of the camper has changed due to advancements in methods, but its method of leaking remains the same.
Here is a front corner molding where I refer to this as a putty tape failure. The putty tape of yesteryear and the type used in 2004, I'm sure, may have different properties and makeup of the tape, but it is still an RV industry issue. This is not unique to Sunline; it is across the industry.
Here is the corner with the molding removed. The black is due to dirt and mold, which have formed as the putty tape shrank and released from the siding and or molding, creating a path for water to seep in. The dirt seeped in with the water, and mold grew as a result of the moisture. Over time, the crack path extends across the full width of the molding, and then water seeps into the walls.
Here is the molding that came off that joint.
And the wood rot that came from the leak.
The same issue of seeping water can occur at any siding penetration point where a hole and screw were made and then sealed with putty tape. The four-corner moldings are often more prone to leaks, as the entire camper flexes on those four corners when towing and making turns. The flexing stresses the putty tape and accelerates the seepage issues. Roof water run off also beats on the corner seams.
Now, how to better build to ward off the problem. I do a multiple-step process to create a lasting seal. I'll show you the outcome of what using the right kind of butyl tape and the right process can create.
This 2007 Sunline 3 years before I ended up restoring it for a friend, the friend reset the front corner moldings himself as a proactive measures using my developed method. To take the roof off and fix the front wall floor water damage, I had to remove those front moldings and I got to see just how good this seal can be.
Here is the back wall moldings on that same camper with the original putty tape. He never made it to the back wall to fix them. See how the tape is not totally bonded to the siding or the molding. It comes off in sheets and loaded with the start of seeping cracks.
Now to the front corners using high quality butyl tape packed in all the siding low spot corrugations, and the molding itself. This was a real bugger to get apart. I had to heat all of it to get the butyl tape to break itself apart, while it was still adhered to both the siding and the molding. This is the type of sealants we want to end up with. It does not release once compressed, the tape itself has to break apart. This is sort of like a wood glue joint, the glue is stronger then the wood when the joint is made right. The wood itself will crack apart and not the glue.
It was that way down the entire joint on both sides. This is what high-quality butyl can achieve when compressed tightly. For it to seal, it has to be compressed tightly, it will not be a good seal just laying on top, it needs the compression.
I also added a second step beyond the high-quality butyl. I caulk the exposed edge of the joint where you see the exposed butyl. This helps with dirt sticking to the butyl, but it also creates a second layer of protection to keep the sun's UV rays away from the butyl.
This caulking method can also be used on any siding penetration that you do not take apart to help seal those joints. See here, this is on our 2004 T310SR (our main camper), which was 3 years old when we bought it. I caulked the front corner moldings as a proactive measure back in 2007. There was an actual start of a leak in the lower front corner that I was not aware of, but I sealed it shut. Then, fast-forward to around 2017, when I took the front bottom siding apart to add aluminum diamond plate siding as a heavier stone guard, and I found this.
You can see the white caulk on the siding I put on 10 years ago. The caulk stopped the leak.
Now you know how the leaks start, and now to how to prevent them.
The corner joint and molding.
After you complete all the woodwork and the siding is clean and ready to install, you install the side wall siding first and bend the tabs of the extra-long siding over the front wall. Staple the tabs in place.
Clean the tabs with a high-flash cleaner (Naphtha or Denatured alcohol) as a final wipe, after the cleaner dries, then put a layer of high-quality butyl down the tabs. Leave the release paper on. Do both sides.
See this link, which will drop you in the middle of a camper restoration showing this process of sealing the front wall siding to the tabs of the long wall siding.
2004 T1950 Restoration Project - (Ugly Picture Heavy)
Next come the corner moldings and how to pack them tight, full of high-quality butyl. See these links, scroll down until you get to the moldings.
2004 T1950 Restoration Project - (Ugly Picture Heavy)
The corner molding ends up like this packed with butyl
Before installing the corner molding, you need to do a final wipe with the high-flash cleaner on the siding of the corner. Then you cut short tabs of butyl and place them into the depressions of the siding. It will look like this.
A rear corner:
This link will take you to the area doing the corners. You want to warm the butyl when putting it on, if your shop if at 50F, if it is 75F outside, it's warm enough. You want the butyl to ooze out and then trim it.
2004 T1950 Restoration Project - (Ugly Picture Heavy)
Once the corners are done with the butyl, then you can go back and caulk the exposed butyl. You can use Dicor non-leveling lap sealant or Proflex RV. I have used both, and both are good. The Proflex has more colors and is better at preventing dirt from sticking to it. This post will explain how to do the caulking. Although it shows all the Dirco work, the Proflex works the same way, using a slightly soapy, wet finger to tool it out.
Dicor Questions
You can wait to do the caulking, you just have to clean everything to prep for the caulk before applying it.
If you are doing this outside, avoid caulk on sun-hot siding; early morning is preferable. And only apply in about 2 feet of length beads before tooling it out. Hot siding, everything cures too fast and will all glob up. Going only in 2 ft lengths allows you time to tool it. If you wait too long, like 6 to 8 ft of caulking, odds are it will be harder to tool out, especially the Proflex.
On the brand of butyl, see this post. I explained it to another member the other week.
In need of some guidance on sealant putty/tape.
If you have a steel building supply house or roofing supply nearby, you want their 20-plus year warranty, good stuff. I linked the GSSI MB-10A I now use, but I used to use Permatite 250H and it is excellent also.
250-H Butyl Tape | Permatite. I just had a harder time trying to buy it by the case, but the tape is excellent. I could really easily get a pallet of it, but I only use about 2 to 3 cases a year. Any commercial building that has specs like the GSSI or Permatite is suitable.
For pin holes in siding corrosion, I use Eternabond Roof Seal tape on the inside of the siding when cleaning it up. This can also work on your bottom metal cover. You stated that Ice Guard is for the bottom cover, and if it sticks, it will be okay on the bottom. But in the siding, it may be too thick, and I'm not sure about the sticking of it. I have used Ice Guard on roof decking, and on the roof, it sticks, but the roof holds it in place. The Eternabond on the siding is thinner, but it will definitely stick. See here on the siding holes patching.
2004 T2475 Repair - Project Camper No 2
Edit: 6/21/25: I forgot to add on the siding corrosion repair, after the Eternabond Roof Seal is applied on the inside, once the siding is installed on the camper, I use Proflex RV clear on the outside of the exposed gray Eternabond to add an extra layer of a seal and to keep dirt from sticking to the area. You can apply the Proflex before installing the siding if you have time for it to cure before installation. Also, use a light, soapy, wet finger to tool out the Proflex.
You are doing great! Hang in there, in time, it is all repairable.
I hope this helps.
John
