How solid are the walls in a class C?

[I-10bound]

Generally speaking, how solid is the structure and walls of traditional class C motorhomes? I'm talking about your Leprechauns, Minnie Winnies, and Freelanders built on the E350 chassis.

I'm trying to comprehend the construction process of these class C's. The way their built, from the inside out, with the walls added last, reminds me of my childhood where I would build little houses out of playing cards. You remember, how you would groove them into the carpet to keep the walls up! I understand why they build them like that, it's more efficient, quicker, and ultimately a lower cost. But when you're used to seeing cars and trucks go down an assembly line with fully enclosed steel frames, it makes me wonder how strong the end product is.

Look I know they don't fare real well in rollovers. But as far as leaning against a wall and stuff, how much pressure can they take. If you're were to brace your feet inside, place your hands on the wall and push as hard as you could, would the wall collapse? Would your hands go right through the wall? If you were parked on the street, could somebody break through the wall with a few wacks with a hammer?

I know these are crazy questions you all. I've been to some RV shows, but you get so taken in by the beautiful cabinets and upholstery, that you don't really inspect much of anything else. Thanks

[Racine96]

Almost all RV walls are about the same 2" thick. Luan, Styrofoam,luan and some fiberglass cover. Usually about 7-11 R factor.

[Joe_T_]

There are a lot of videos on YouTube showing RV construction. I think you will find them interesting.

Joe T.

[I-10bound]

Hey guys, thanks for the posts, including the pictures!

I went to a dealer a few days back, they had beautiful new Minnie Winnie 22's. Out of curiosity I put my hands on the exterior sidewall and pushed, kind of rocking the coach. I didn't realize that a salesman was inside showing it to a lady. He popped outside and said, what are you doing? I told him I've seen these things completely disintegrate at a monster truck show, and I was testing the walls. He joked, "you break it you bought it!". Maybe next time I'll bring my sledgehammer, just kidding.

[Bordercollie]

RV's and contents tend to be heavy vehicles and somewhat top heavy. The overall weight of the house-box needs to be kept reasonably light. Modern RV's house boxes are probably lighter than 70's vintage ones for reasons of handling and load carrying, rolling resistance/mpg.

[BruceMc]

Here's a breakdown of the wall:





Where the tin is the inside lining underneath the coach. I cut a hole through the skirt to gain access to a gray water drain valve that the factory thought it was better to crawl under to access...

All framing in the last several years is welded square-wall aluminum, then as you see, expanded foam insulation (as compared to the brand Styrofoam, which is extruded foam) laminated with luan on both sides, then the fiberglass/plastic sheet. All is glued up, and is very rigid until water intrudes and separates the plys of the luan... arg! But the structure is still very strong.

I remember tin-sided rigs where all the framing was 2x2's and fiberglas insulation.... Yes, even earlier motorhomes were built using this construction technique! I think federal regulations stopped that practice sometime back in the 70's or 80's. I think.

Hope that helps!

[Harvey51]

Incidentally, while car frames are pretty strong, the skin of a car body these days is quite thin metal and it's not at all hard to dent or deform it with plain muscle power.

This brings to mind a fund raiser for breast cancer held in our community a couple of years ago. A car 10 or 15 years old was painted pink and people paid $5 for three hits with a sledge hammer. A good deal of money was gathered but the car was not seriously damaged. I guess they were tougher in those days. It was a fun fundraiser, though.

[Chum_lee]

thestoloffs wrote:
There are Class C's in every size range that are built solidly behind the cab, with steel roll-bar framing and fiberglass walls with insulation. But, these cost a pretty penny, because they usually aren't produced on large assembly lines.

If you really want/require this kind of construction, these brands are well known. Start looking for used models everywhere, including their brand owners' clubs.

Otherwise, realize that you're putting a tiny house on top of a van chassis, and adjust your expectations according to your expenditure.

The "house of cards" scenario is generally right on. In any major crash, roll over, solid impact, or whatever, you (and everyone/everything else) best be strapped in because the house structure gets destroyed very easily. The exception is when you are built on a class B/C van chassis. The front occupants are generally safer than in most class A's.

Search Youtube for crash results. It ain't pretty. IMO, The overall mass is your only saving grace.

Chum lee

[thestoloffs]

There are Class C's in every size range that are built solidly behind the cab, with steel roll-bar framing and fiberglass walls with insulation. But, these cost a pretty penny, because they usually aren't produced on large assembly lines.

If you really want/require this kind of construction, these brands are well known. Start looking for used models everywhere, including their brand owners' clubs.

Otherwise, realize that you're putting a tiny house on top of a van chassis, and adjust your expectations according to your expenditure.

[Deb_and_Ed_M]

A truly determined person can whack through just about anything, including a frame-built house? (cinderblock might take a while) Firemen do it all the time.

I think the walls of our 5th wheel were thicker than our 2004 Class C (an entry-level model) - but in the whole scheme of things, I'm not sure an extra 1/4 or 1/2" of foam really matters. And when I think of all the "adventures" our Class C endured, including seriously rough Alaskan roads and some off-roading - it handled everything very well.

[DrewE]

A laminated wall is actually quite strong--certainly stronger than the layers are separately when not attached to each other. It's similar in concept to a hollow core door for a house. A hollow core door is entirely strong enough to use as a desk or table top, despite the skins being very thin plywood, since it's acting as a box beam rather than a sheet. (I speak from experience about the doors; in fact, I'm sitting at a desk composed of a door and two file cabinets that I've used for over a decade and a half.)

An RV wall, if the framework is solid, should be able to resist leaning against it and pressure that isn't completely localized quite well. It will not do so well against a maniac with a hammer or hatchet (though probably the windows and especially skylight would be easier to break through), nor a serious crash on the road, nor a tree falling on the unit. They will also lose a lot of strength if the materials or construction is compromised, say from rotting due to water intrusion.

Incidentally, while car frames are pretty strong, the skin of a car body these days is quite thin metal and it's not at all hard to dent or deform it with plain muscle power.

[ksg5000]

I don't think the walls of my Jamboree are any different than the walls of most of the Class A's. As far as "roll over test" .. your SOL in any RV that I have ever been in.

[ScottG]

They are strong enough for any reasonable use and the structure is really the last thing you have to worry about.
I'd be more concerned with roof construction.

[Snowman9000]

I think they are strong enough for the destructive tests you are suggesting. As far as hacking into them, once you get through the fiberglass exterior, there is only foam insulation and then a thin layer of paneling. Except for the framing pieces of course.

I do think you don't need to worry about it. They are strong enough for the job.