Steel stud construction techniques

tirod3

Active member
Tiny home builders have embraced steel stud use, but it's not a common skill in the DIY homeowner world. It's becoming more well known as outdoor kitchens are often built using them. Another area is DIY campers - a steel stud weighs less than a 2x, offers simply assembly, and has the advantage, like most materials, of becoming proportionally stronger as the size of the project grows smaller. Cold formed steel is galvanized, which lasts longer if techniques fail to prevent water ingress into the structure, and also does a great job supporting more weight - commonly, gypsum board - than most campers will ever see.

The RV conundrum comes up tho, a moving habitat sees a lot more dynamic stress than a stationary one, much like "destination" RV's aren't really suitable for hauling across America - they shake apart even faster than the more hardened ones. Living in a mobile domicile that has to experience hurricane force winds - yep, 75mph is that threshold - and also get shaken by Category earthquake rattling, such as the bypass around Amarillo TX. Bad concrete design led to curved road plates that rise at the ends, it's a huge washboard of thumping worse than highway 69 in Oklahoma, which is saying a lot.

Stick and tin get pounded as it is, it's arguable that a stiff structure of panels helps as it would transmit the forces rather than accommodate them, beating the interior furnishings, appliances, etc. Our off road campers tell us its the same on unpaved roads at speed, washboard and potholes will redistribute loose cargo in the beds of their trucks - and those have tuned suspensions with shock absorbers etc to minimize it. Of course, just slowing down is never an option . . .

PDF at link that discusses the techniques of steel stud framing for the interested DIY looking for a different method. I found it researching whether to double screw studs to each other, adding more reinforcement to the joint rather than a single screw that stationary construction gets away with. The opening paragraph caught my eye comparing steel stud to timberframing, and the PDF goes into lateral reinforcement, something stick and tin production builders have notoriously ignored over the years. Those welding up their own aluminum tubing framework might pull out information, too.

If we are going to DIY, being a knowledgeable builder helps to maintain structural integrity of the unit. As for where this fits into the panoply of techniques, it could be said it's making interconnected panels that create a floor, wall, or roof and how they meet a performance standard. There are few standards of construction in the RV industry and of late consumers have begun to notice.

Link auto connects to a .gov PDF for those who are appropriately wary. Your tax dollar at work.

 

tirod3

Active member
Here's a short excerpt from an Australian testing company on K bracing vs X strapping.

And, BTW, if these posts are AI, they are well beyond the normal junk filling the internet these days, and don't make up facts and figures like much of it. However, the typical reaction of less well educated people is to deride what they can't understand, which might be the real problem here.

 

Ozarker

Well-known member
Had a garage built for powder coating, it had a large vent van in an upper end wall. Studs were double screwed as mentioned. In less than a year, fan vibration caused joints to become lose, screw holes enlarged, exterior sheathing held the wall together. Wall area was torn apart, new studs installed, joints were spot welded, all was good thereafter.

I don't think you could put enough screws in metal studs to hold joints tight in any vehicle application, spot welded.....maybe, a welded bead may be required.
 

tirod3

Active member
Rivets loosen up, too, as Cobra kit car builders have reported. I considered the screws might back out and decided thread locker would be one solution. Even construction adhesive, but the use of screws in existing RV's shows it's not a big problem, much less staples in wood. Plywood teardrops are getting built with deck screws and its not discussed as a problem. And while there may be examples of how it didn't work, what we often discover is that the installation didn't follow workmanlike rules for that technique. If I was stapling aluminum skins to untreated wood to make a camper, it would be better to use glue coated staples to get them more secure.

There is no perfect solution, and no, I would not recommend welding galvanized. Worked a a commercial supplier in the 90s bidding hollow metal frames and hardware, the frame supplier would ship galvanized which was primer coated and no notice until the welder smelled the different odor. It's toxic.

Later worked at a truck body manufacturer locally and they actually spent money on a fume collection system to stop a days worth of welding from reaching an OSHA trigger point. But they couldn't afford press brake dies and clamps for my Amada brake to handle aluminum step tread, and the fire engine project died quickly because there was no way to keep parts in spec. I'm aware of "issues" and how they come up.

Some TL;DR on the two links to get the nuggets out:

1. You can use as many screws as you can line up across the joint, stacked deep. Of course, two would be enough to keep the stud from wiggling as much when racked. Steel is superior compared to wood in that regard, and its also consistent in material with no defects.

2. Angle clips at the bottom and top of the stud will help anchor them. More screws!

3. Get the stud all the way down within 1/8th inch of the bottom plate/ top plate, to make support for the vertical load, instead of suspending it from the screws.

4. Cross bracing is superior to K braces, the attaching points use webs with enough screws to make the actual brace the "weak" element. The intent is to get the brace to stretch in extreme circumstances under static construction policy. With a mobile application, trying to keep it in one piece as its rolling over at 75mph on the freeway would be a huge improvement compared to stick and tin. "Oh look honey the gun safe just popped out and hit that bridge abutment."

With wind loads in a storm, using corner braces to guy it down could at least keep it from getting inverted. Helene/Milton showed what happen to RV's with 125mph winds and there was even a photo of a home tied down with 4" trucker ratchet straps. No report on how they did. After a certain point nothing will work, as the EF5 here in 2011 showed, but if you can tie down for milder weather it would help. They do that with tents a lot, i've seen. In extremis, you knock down the tent poles and ride it out flat on the ground. An RV can at least try to vacate the county IF owners would just keep a weather eye out.

5. The positive of being built by labor from smaller pieces means the entire floor, sides, and roof can be assembled indoors under cover then brought together where necessary to join the panels. << And there is that word: Panels. View the construction tech as building a reinforced panel with bays that hold insulation, already clad with the skins attached (which take stress just like fiberglas or carbon fiber) and it becomes similar to those expensive panels already used in the RV market. RV's are now built that way, one huge side panel, etc.

6. You can build curved shapes - just V notch the steel stud on the sides with tin snips every few inches and then bend the stud against a form. Some weld them to retain the shape, I'm thinking don't make wide V's and then screw the overlap together to secure it. One method of bending is to layout the sketch on a concrete pad, then simply drill holes along the outline for pins to help knock it into shape. You can repeat that for dozens of additional parts. For the DIY, it's much like the huge bending table seen in factories, but you use an existing workshop floor. Cheap.

7. Steel is 1/3 to 1/2 the weight when framing up a domicile compared to normal 2x stick. It's rot proof, is often made from recycled scrap which means nobody cut down trees, doesn't need harsh chemicals to stop rot unlike most treated wood, with galvanizing is highly rust resistant, easy to handle, takes simple hand tools to cut and fasten. And, it's very similar to the original RV - Airstream - which is all aluminum that is hand riveted with hundreds of fasteners. They "buck" the heads on those by hand forming the opposite side.

Who was the first person to build a fiberglass foamy? What a weird idea, carve up some cooler foam and then slobber resin over cloth for a camper? Yet, it's taking off because it works. There are stages of acceptance to new ideas, initial resistance, initial market introduction, allowing others to be beta testers, then acceptance that skilled pro's can do it, finally, it's DIY. America is about 30 years behind steel stick construction compared to Europe, strangely enough, and reading the links reveals we are getting the benefit of their research into what does and doesn't work.

Of course, some refuse to accept that solar generators are a good idea, so, I get how hard it might be to accept steel stud construction. Gosh.
 

Peter_n_Margaret

Adventurer
Who was the first person to build a fiberglass foamy? What a weird idea, carve up some cooler foam and then slobber resin over cloth for a camper? Yet, it's taking off because it works.
In aviation, it was in volume production in Germany in the H301 Glasflugel Libelle in 1964. That is 60 years ago.
There were numerous one-offs produced well before that.
These are high speed, high performance, competition aircraft. Many of those original aircraft are still flying today, after 60 years of flying.
It took Boeing 48 years to catch up. 48 years!
Cheers,
Peter
OKA196 motorhome
 
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6912

New member
the FT owns 9 RV repair shops. DIY steel frame trailers make so we pay cash when opening a new repair shop . steel will have condensation so dry-rot wood. Steel and alu-bond type crap will be gone in 15 are so years there are ways to build a 4-year-old can do that last 100 of years with less cost .But we would not having all the cash cows coming to the shops
 

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