Ditching the coroplast for something better

[acooper1983]

has anyone ditched the coroplast for something a little stronger/higher quality. It might be my ocd, but coroplast looks like a hammered dog turd every time i look under a trailer. My thought is using 1/8" HDPE. Its is EXTREMELY durable , my thought was to use adhesive and attach 2" closed cell construction foam for better under trailer insulation, then attach with sell tapping screws to the frame, im guessing i will have to add a little bit if cross bracing for the seams to be tied into, on could then simply caulk, or tape the joint lines (perhaps a butyl gasket) To fight moisture under the trailer, my idea was to add a "radon" fan and piping for air movement when needed.

[rhagfo]

has anyone ditched the coroplast for something a little stronger/higher quality. It might be my ocd, but coroplast looks like a hammered dog turd every time i look under a trailer. My thought is using 1/8" HDPE. Its is EXTREMELY durable , my thought was to use adhesive and attach 2" closed cell construction foam for better under trailer insulation, then attach with sell tapping screws to the frame, im guessing i will have to add a little bit if cross bracing for the seams to be tied into, on could then simply caulk, or tape the joint lines (perhaps a butyl gasket) To fight moisture under the trailer, my idea was to add a "radon" fan and piping for air movement when needed.

Yep, I think you are over thinking it.

[acooper1983]

I disagree, I use this trailer hunting in some fairly cold weather, I think this will allow me to not have to dry camp during november deer seasons, combined with pad style tank heaters It will also increase the efficiency per lb/lpg burned.

[bobbecky]

As long as the coroplast is intact, no unsealed holes and is fully attached to the frame all the way around, I doubt you will gain any measurable savings of propane usage. We've been in single digit temps with our coroplast covering, and I have never noticed heat escaping from underneath. Besides, heat rises, so it will usually be warmer in the living space. You will probably gain more heating efficiency with dual pane windows than you will with changing the belly material.

[Frank G]

1/8" HDPE normally is not very flat in 4' x 6' sheets, and that depends on the extruder. The plus side it is almost indestructible and has no known solvents at room temperature. If you do some hunting you can find some H extrusions to join the sheets. You will probably have to buy them in 4x8 sheets. Sabic Polymershapes may be a good source. Other materials like ABS or ACM (aluminum composite material) would work but not as forgiving as HDPE. Take a look at the 3 mil ACM, that would make for a good looking underbelly. They make it in "Good One Side" so slightly less than "Good Both Sides". This stuff also comes in sizes up to 5 x10, and is available through sign shops.

[notanlines]

I believe someone pretty sharp earlier said it....yep, overthinking it.

[acooper1983]

I dont believe im over thinking anything, Im not sure that one can have too much insulation under a trailer can you? if that was the case, no one would skirt trailers right? coroplast offers little if any R value, so you're relying on your one or two ducts under the trailer for you heated underbelly, this seems like wishful thinking if you truly want to use your unit in cold weather. I've found tons of threads where people have insulated the bottoms of there campers temporarily when living in a unit through the winter up here where we see temps get into the deep negatives. I want something that offers better Rvalue as well as being able to travel with it, hence where the HDPE comes into play. I dont consider that over thinking at all, i consider that an intelligent solution to a real problem with pretty much any RV with an "cold weather" or "artic package" I will admit that i could probably get away with dropping the coroplast, addint insulation and tank heaters and re-installing it, but as stated previously, its a cheap looking product. Its soley used because its cost effective by mfg, there are much better products out there.

FrankG. Thanks for your well thought out and concise response, its appreciated. I have a source for all the HDPE i need, as well as the "H" connectors if i decide you use them, im on the fence as of now as i think i might want to edge screw each 4x8 section to a cross member with a butyl gasket (like in dust collection/hvac systems) So i can drop a single panel at a time if i so choose. I will look into the other products you mentioned as well.

[KeithInUpstateNY]

I have boondocked in my trailer here in upstate NY until the end of October, first week of November, where we regularly get overnight temps in the low twenties the past three years. I sealed all the larger gaps along the edges of the chloroplast with caulk and taped the entire perimeter with foil tape, leaving about a four inch gap in the back where it fit tight so that if I did have a leak in the underbelly it would have a place to drain and I'd be aware of it. (I had a shower drain leak on my maiden outing and only discovered it when I tilted the trailer to hitch up and water poured out the back.) I have thought about dropping the chloroplast and adding a layer of Reflectix and reinstalling the chloroplast, but I haven't done it yet.

Another thing I did that made a big difference in comfort is insulate the top and living space side of the pass through storage with rigid styrofoam glued and strapped in place. The mattress stays much warmer now.

[acooper1983]

I have boondocked in my trailer here in upstate NY until the end of October, first week of November, where we regularly get overnight temps in the low twenties the past three years. I sealed all the larger gaps along the edges of the chloroplast with caulk and taped the entire perimeter with foil tape, leaving about a four inch gap in the back where it fit tight so that if I did have a leak in the underbelly it would have a place to drain and I'd be aware of it. (I had a shower drain leak on my maiden outing and only discovered it when I tilted the trailer to hitch up.) I have thought about dropping the chloroplast and adding a layer of Reflectix and reinstalling the chloroplast, but I haven't done it yet.

Another thing I did that made a big difference in comfort is insulate the top and living space side of the pass through storage with rigid styrofoam glued and strapped in place. The mattress stays much warmer now.

Excellent insite Comp! thank you. I need to look at my pass through and consider doing as you have done, solid advice!

[KeithInUpstateNY]

You're welcome Coop, and thanks.

A friend who teaches college level physics pointed out that the other thing to think about when sealing up the underbelly is that the warm air from the underbelly duct needs an exit for it to be able to flow around the plumbing components, which is really what we are concerned about. In my case the hole around the plumbing under the tub is bigger than it needs to be. I intended to foam it, but he suggested leaving it and taking the access panel off so the warm air could be pushed back through the plumbing hole and into the living space. I think this year I will look for a vent to replace the solid access panel to help insure I don't also get any welcome guests.

Hopefully one of the moderators with more knowledge about real life RV construction will weigh in.

[chuckster57]

Hopefully one of the moderators with more knowledge about real life RV construction will weigh in.


I’m thinking you mean this moderator. I’ve seen open underbellies, coroplast only, coroplast with a thick “foil” liner and all the above with R19 batten shoved in. Since I live and work in an area that doesn’t see frigid temps, I don’t have any first Hand knowledge of what’s the best.

If I was considering what the OP is, I would probably just buy kraft faced insulation, unroll it and feed it in the gap between the coroplast and framing. If it’s held in place with self tapping screws it’s an easy task. Rivets can be removed and replaced with self tapping screws.

If your going to try this route, I would only take the fasteners off a few at a time, stuff the insulation and then replace the fasteners before moving on. It’s near impossible to put it back exactly like it was if you drop a large section.

[rhagfo]

I have boondocked in my trailer here in upstate NY until the end of October, first week of November, where we regularly get overnight temps in the low twenties the past three years. I sealed all the larger gaps along the edges of the chloroplast with caulk and taped the entire perimeter with foil tape, leaving about a four inch gap in the back where it fit tight so that if I did have a leak in the underbelly it would have a place to drain and I'd be aware of it. (I had a shower drain leak on my maiden outing and only discovered it when I tilted the trailer to hitch up and water poured out the back.) I have thought about dropping the chloroplast and adding a layer of Reflectix and reinstalling the chloroplast, but I haven't done it yet.

Another thing I did that made a big difference in comfort is insulate the top and living space side of the pass through storage with rigid styrofoam glued and strapped in place. The mattress stays much warmer now.

Well we full time along the Oregon Coast in winter, see temps below freezing down to mid 20's. Our 2005 Copper Canyon is maybe rated a a three season 5er at best, the underbelly was open. I sealed with coroplast and Reflectix, and floors are noticeably warmer. We also heat with the Cheap Heat system, at 5,000 watts no issue that cold, when on a 30 amp service and 1,800 watts, need to use gas to change temp up, but 1,800 watts will hold to the mid 30's, in a 32' 5er.

I would not place any fiber insulation in the underbelly as all will absorb water, Rockwool included!

[chuckster57]

I agree that fiber insulation will absorb liquids, it is a big mess when you lose a hydraulic line. That said, we see it used a lot.

[acooper1983]

Thats was my thought as well, on batting style insulation. I have access to a spray foam rig, but I havent done any calculations as to weight. We camp fairly light as a rule, but i dont want to put so much weight as im getting too close to my axle limits. I figure the hdpe and 2" closed cell will cost me couple hundred pounds and i can live with that number

[chuckster57]

Spraying foam would make it a real PITA if you have to do any electrical or plumbing repairs.

[wiredgeorge]

I agree that fiber insulation will absorb liquids, it is a big mess when you lose a hydraulic line. That said, we see it used a lot.


We live in a pier & beam house on the side of a rocky hill in the Texas Hill Country. Last Sunday, had a pipe fitting break under the house and the underside is covered with a chloroplast type plastic stuff and chicken wire below that to keep critters from ripping up the sheeting. Our floor WAS decently insulated with batt fiberglass insulation (16" wide) and the insulation was soaked and the chloroplast type stuff was hanging down a foot or more in two places where the insulation had sucked up the water from the broken fitting.



Got the water shut off and Monday had a plumber come in and fix the leak and yesterday crawled up under the house (no fun) and cut the chicken wire and plastic and pulled out a bunch of very heavy and soggy insulation. That is far far better than spraying in foam insulation which would have been a complete disaster as I am pretty sure the water would have not gotten into the sagging plastic but done damage to the floors in the house. Today going to find some fans and dry things out before proceeding to put things back to what they should be.

[daveinaz]

If your going to try this route, I would only take the fasteners off a few at a time, stuff the insulation and then replace the fasteners before moving on. It’s near impossible to put it back exactly like it was if you drop a large section.

That's the truth! I found that out the hard way when I dropped entire sections of it at a time replacing a hydraulic hose.

[cookinwitdiesel]

Just an FYI, skirting the trailer is to make a static air gap which helps insulate the underside of the trailer. If it is open, you will constantly lose energy through the floor, but if that area is not free flowing, than once the air is warmed some, it creates a barrier between your floor and the truly cold outside air. It is the same principle of why bridges freeze over before surface roadways, the air passing underneath them constantly pulls out energy dropping their temperature.

So the air itself is providing the insulation - the foam skirt is just to keep that air in.

[Steveo57]

I've taken the coroplast off mine and installed a layer of reflectix when I put it back up. I cut the coroplast into three sections and added some PT 1x4 at the seams to give me something to screw the seams down tight. Then taped up the seams also. Mine just has a 2" duct coming off the furnace that drops into the underbelly so not a lot of heat gets down there but if you seal up the underbelly good (better than what you get from the factory) it should work better than nothing. The other thing I did was to insulate the PEX water pipes to try and help out.

I'll have to check into leaving an exhaust path for the warm air. I sealed up all the holes into the trailer as a second barrier in case something gets into the underbelly. Might consider putting a screened vent somewhere.

[daveinaz]

That's what I'm going to do -- cut the coroplast into smaller sections, then use 3m spray glue to attach the factory "insulation"/shiny bubble wrap to the top side of the coroplast, then put it back up in more manageable sections. Then I'll put gorilla tape on the seams and spray foam where any pipes come out the bottom.

[sourdough]

That's what I'm going to do -- cut the coroplast into smaller sections, then use 3m spray glue to attach the factory "insulation"/shiny bubble wrap to the top side of the coroplast, then put it back up in more manageable sections. Then I'll put gorilla tape on the seams and spray foam where any pipes come out the bottom.


Dave, when you cut that coroplast you might use one of these products to seal the seams;

https://www.amazon.com/Surface-Shields-BP4180-Shield-Repair/dp/B002SSGAZG/ref=sr_1_5?keywords=scrim+tape&qid=1550882103&s=gateway&sr=8-5

https://www.amazon.com/Mobile-Belly-Bottom-Repair-Fix-Underbelly/dp/B00BJ5SPO8/ref=sr_1_1?crid=ZZ8HAJENML06&keywords=flex+mend+tape&qid=1550882202&s=gateway&sprefix=flex+mend%2Caps%2C159&sr=8-1

I have read that the gorilla tape will let go and peel over time. Chuckster has said, if I recall, that "scrim" tape is what they use to seal the seams on the coroplast. I have bought the flex mend because it appears to be the same thing as scrim tape but scrim tape is pretty expensive. I have not used the flex mend yet; I have taken a piece off and just "tested" it and it seems like it ought to be pretty good. Just some options.

[KeithInUpstateNY]

Looks like a nice neat job steveo57.

[daveinaz]

Dave, when you cut that coroplast you might use one of these products to seal the seams;

https://www.amazon.com/Surface-Shields-BP4180-Shield-Repair/dp/B002SSGAZG/ref=sr_1_5?keywords=scrim+tape&qid=1550882103&s=gateway&sr=8-5

https://www.amazon.com/Mobile-Belly-Bottom-Repair-Fix-Underbelly/dp/B00BJ5SPO8/ref=sr_1_1?crid=ZZ8HAJENML06&keywords=flex+mend+tape&qid=1550882202&s=gateway&sprefix=flex+mend%2Caps%2C159&sr=8-1

I have read that the gorilla tape will let go and peel over time. Chuckster has said, if I recall, that "scrim" tape is what they use to seal the seams on the coroplast. I have bought the flex mend because it appears to be the same thing as scrim tape but scrim tape is pretty expensive. I have not used the flex mend yet; I have taken a piece off and just "tested" it and it seems like it ought to be pretty good. Just some options.

Let us know how that flex mend works -- it certainly look like a more economical option over the Scrim tape.

[sourdough]

Let us know how that flex mend works -- it certainly look like a more economical option over the Scrim tape.


"Hopefully" I won't have any need for the tape in the foreseeable future. I bought it, along with lots of other stuff, for a "what if" situation. I believe it can also be used on the Darco fabric under my slides so it figure it might come in handy one day.

[Frank G]

"Hopefully" I won't have any need for the tape in the foreseeable future. I bought it, along with lots of other stuff, for a "what if" situation. I believe it can also be used on the Darco fabric under my slides so it figure it might come in handy one day.

I used some Gorilla Tape on the Darco under the slide. The first time "in" the tape got all snarled up on the plastic bottom support and created quite a mess. I am still looking for something to repair some small screw holes in the darco.

[sourdough]

I used some Gorilla Tape on the Darco under the slide. The first time "in" the tape got all snarled up on the plastic bottom support and created quite a mess. I am still looking for something to repair some small screw holes in the darco.


Frank, I'm not sure what the true answer is. My trailer had 3 patches of what I assume is/was scrim tape under one of the slides on the Darco. No apparent reasons for it but they did start to turn up just a tiny bit on the edges = looked like one of the tapes I posted. Thankfully they were in the middle of the slide (somewhat bowed up) and didn't have a lot of wear from the wear bar. Fixed that with the poly? strips I placed under the slides.

[Fishsizzle]

I look at the underbelly and it makes me cringe. Lots of little just gaps etc. I’m going to drop it and foam/insulate where needed. Then use double sided foam tape like you would used on a truck canopy to seal it up better

I have a basement model, and I want to hard foam the inside of it as well. In between the aluminum sub frame, front compartment as well.

It might be overkill. The front and basement do not have any floor insulation, and the doors are thin to outside.

[BulletOwner1]

Here's an option, skirting. Expensive probably but a LOT less crawling around under the RV. If I was full time I would look into that further. Especially if I planned to spend more time in colder areas. Of course that could have included most of the southern states this year :lol: .

I did the aluminum foil bubble wrap stuff on my Bullet. Real pain, and not sure how well it worked but made me feel like I did something. Also allowed me to reroute some of the heater ducting. Couldn't believe the "workmanship" used by the builders.

Be very careful when installing/reinstalling the underbelly. When removing the coroplast make sure the shorter screws go back in the same place. They are shorter for a reason. I learned that AFTER I screwed into the bottom of my fresh water tank :facepalm: . That's when I learned how to repair plastic......

[goodellj]

Thanks for all the useful discussion about dropping the coroplast. I have a 2012 Montana 3150RL and there is an intermittent leak in my kitchen gray tank, which is over the 2 axles. When I get home in April I plan to unbolt the coroplast from the frame (and replace the bolts with SS!), get a good look at the tank to determine the leak, and then decide how to repair it. I was wondering how to remove the coroplast to get at the tank because with the axles in the way, spare tire under-mounted through the coroplast, and other various warts, wires, propane pipe, and protrusions, it might be hard to actually get the coroplast completely off in order to do the work.

I would love to get the entire sheet off to expose the tank but it may not be possible. I was hoping to locate the leak in a position that I might be able to reach it. I might have to cut out a flap or a section of the coroplast. I may look into H-extrusions for rejoining the sheets and/or replacement sheets (thanks FrankG), or Gorilla Tape (thanks Ray).

Ray at Love Your RV had a full video and discussion on removing and reattaching the coroplast underbelly:
https://www.loveyourrv.com/reinstalling-the-cougar-fifth-wheel-underbelly/

There has also been several useful discussions on repairing leaky tanks and installing extra supports for the tank (thanks Rohrmann).
http://www.montanaowners.com/forums/showthread.php?t=72308
https://www.loveyourrv.com/repairing-cracked-rv-waste-tanks-with-plasti-mend/

[BadmanRick]

Just remember that changing the factory under belly with something else May add a lot of weight for which the trainer was not designed for. Just saying otherwise just buy a n extramarital cold weather trailer.

[Nearreality]

If insulation is the issue I cut hatches in the corroplast and stuffed the underbelly with r38 fiberglass and it made a big differance. I used gorilla tape and a heat gun to seal the hatches back up. Hdpe is durable but it probably will not have the structural stiffness of corroplast.

[jimborokz]

Last winter in our then new 3731FL to verify the effectiveness of the basement heating I put a transmitter for our indoor/outdoor thermometer behind the area where all the plumbing converges. In temps that ran down into the teens the basement maintained 58 to 60 degrees. That's with no added insulation beyond the factory.



In my stick built house I have Hydronic radiant heat in the floors. They used the bubble wrap insulation under the floor joists to keep the heat going up to the rooms. This is the same insulation the factory puts above the coroplast. My experience is it gives the equivient of R13 fiberglass blanket insulation. It's uneffected by water if there is a leak. Remember heat rises so there is not much loss going down thru the coroplast.

here is what they used:
https://www.homedepot.com/p/Reach-Barrier-2-ft-x-125-ft-Double-Reflective-Insulation-Air-Roll-with-Double-Bubble-DD24125/204476654

[plocklin]

has anyone ditched the coroplast for something a little stronger/higher quality. It might be my ocd, but coroplast looks like a hammered dog turd every time i look under a trailer. My thought is using 1/8" HDPE. Its is EXTREMELY durable , my thought was to use adhesive and attach 2" closed cell construction foam for better under trailer insulation, then attach with sell tapping screws to the frame, im guessing i will have to add a little bit if cross bracing for the seams to be tied into, on could then simply caulk, or tape the joint lines (perhaps a butyl gasket) To fight moisture under the trailer, my idea was to add a "radon" fan and piping for air movement when needed.




Coroplast does very little to insulate the underbelly. It does seal out wind and moister. I put R30 in my underbelly. I hung ½” emt to support the cheap-o plastic liner. It is very light and strong enough to support the sagging.

I also added electric heat pads to my water tanks and pluming. Make sure you put pads on any long drain runs and near any dump valves that are not mounted directly onto a tank.

I did a thread about camping in Angel Fire NM this Christmas. It got down to -24f one night and we stayed warm. We were one of a few in the park that had running water in our trailer.

Angel Fire RV Resort During Christmas? - Keystone RV Forums (http://www.keystoneforums.com/forums/showthread.php?p=310711#post310711)

Cheers!

[Rubicon100]

We pull our camper out to our hunting property in October and leave it set up until the week before Christmas.
We have access to electricity but nothing else and when we aren't out there I set the thermostat for 45 which is the lowest it will go and we keep a couple of spare propane tanks there, I didn't winterize it until we were getting well below freezing and I was surprised how little propane we used. This was our second year of doing this and I have to say it's awful nice driving out and having a warm place to stay. If you do change the coroplast let us know how it goes as I may be interested in trying it myself.

[kjohn]

BulletOwner1 suggested skirting. Skirting around the perimeter is what I see lots of up here in Western Canada. Works okay if you are staying in one place. People live year round in RV's when work requires it. Just remember to allow for some air circulation, or moisture will become a problem.