Container Home Cut-Outs…

21 Dec

Greetings, Campers!

I know, I know…

It’s “the holidays” and we’re supposed to be “nice” and play with the kids, and negotiate truces with the neighbors, and wait patiently for Santa to get here…

Hey, he brought it on himself. He’s ruining the economy!

… so we can knock him on the head with a pipe, and take all the toys for ourselves…

Um… Oh, crap. I said that out loud, didn’t I? Oops.. My bad. 🙂

Well, I thought that before this year is over, I’d get one last big “Container Home” rant out of the way.

So, I’m putting the “Ho-Ho-Ho”… on “Ho-Ho-Hold”… for a minute or two.

And… If you don’t like it, you can just start clicking that left mouse button now… 😉

Anyone who has been here before knows that my family is building a home out of Corten Steel Shipping Containers, to replace a home that was destroyed by Hurricane Katrina.

And, it’s certainly not without it’s trials and tribulations.

Our circumstances are anything but ideal and we’re trying to put out several fires that are all burning simultaneously.  Suffice to say, we’re planning, scheming, and eventually even building… with our hands full.

And if we can build our Container Home, with the veritable whirlwind of crap that is encircling us…  then so can you.

I told you a while back that I was going to start answering question from my email, right here on the blog.

Why? Well, it’s fun… for starters! Some of the situations are almost comical.

Like this one, that plays right into my “Kick some of those rats at Planning and Zoning right in the butt as often as possible” sinister plans… Muwahahahahah! :

Hey Ronin,

I’ve just submitted some Container Home plans at my town’s planning and zoning department, with my application for a building permit.

And they are telling me that they need an engineering report that details how the alterations made to the skin of our 40′ high cubes reduce their strength.

We’re building a one story,  1,540 square foot home, using (5) containers.

The container sit “side by side”, (5) across to form a 40′ x 40′ box. There are several bearing walls inside, to help hold up the roof.

We’re altering the containers by cutting out holes for doors and windows.

I talked to the guys I bought the shipping containers from (they’re well-established and move a lot of containers) and they are working up the job report (cost analysis) of making the alterations, but even they have never been asked for any engineering  analysis “for the openings” before.

They were actually surprised, because after calling around, nobody else that they deal with has ever been asked for anything like this before, either!

I told the planning and zoning guys that the strength from an ISBU comes from the framework, but they are still demanding “hard numbers.” We are currently working with a local engineer, but he has no experience with shipping containers at all, and it would be helpful to connect him up with someone who does.

What do we do?


Hating Math and minor bureaucrats…

Dear Math-hater,

Here’s my “Q&A – Wisdom for the week.” Get it while it’s hot, because my brain cells rarely touch, and this may not repeat itself again for a while! This “holiday season… is anything but…” Oy.  🙂

Note to readers: THIS is what he’s talking about. He’s made holes in his Containers, to place doors. It probably looks something like this… It’s what mine look like after I cut them up. I love plasma cutters! 🙂

While I’m quite used to hearing all about these Planning and Zoning Nazi gyrations (you just have to read my blog about my ISBU Home Building exploits to see some of the gymnastics you are forced to go through):

This particular request for an engineering report (from whoever asked you for it) borders on the ridiculous.

There’s a reason that your Container Fabrication shop hasn’t been asked for these “numbers’ before…

There AREN’T any really pertinent numbers here, when you’re talking about a single story residential structure…

The steel skin on a shipping container is just a couple of  millimeters of corrugated steel skin. It’s jobs is to contain the boxes full of cargo held within the box it forms…  not to maintain pressures from outside the box.

That’s why that skin is “inset” inside the frame. Even IF it could make a difference, it could only have an effect during “heavy weather or loading” racking or shearing force deflections. The frame bears the brunt of the loading.

And even then, the skin’s contribution is very minimal.

You’re not building a wood house out of sticks. “Not by the hair of your chinny-chin-chin…”

I suspect that is the origin of your “engineering report” request. The guys that you are talking to are used to dealing with wood homes.

If you understand the design of the modern shipping container in it’s raw form, the POINT is for the frame to carry the load, and allow it to be used in a “track and stack” deployment, while loaded with thousands of pounds of cargo, per container.

(“Track and stack” just means that someone supposedly charts where each container actually gets placed.)

The reason this container is so vital to shipping is in part due to it’s ability to be connected to another series of containers, FRAME TO FRAME, forming a giant “honeycomb” like structure. This “structure” is capable of absorbing and deflecting tons and tons of pressure, safely.

FYI: Just don’t get carried away; Remember, Corten Campers…  “over 9 high and you’re gonna die…”

I’ve heard people address this kind of “stress reduction nonsense” when talking about applying siding or even insulation to the outside of the boxes. Here’s the other side of that “skin stress” coin;

(Might as well kill two birds with one post, huh?)

I once had a contractor tell me that if I put hardiplank on my boxes, it would double their strength.

He got really irritated when I laughed right in his face.

Needless to say, he was just trying to sell me his stockpile of siding. It’s nonsense. Siding is attached to containers thru the use of wood firring strips, If your container racks that  much, those nails or screws will pop out like firecrackers.

Using closed cell foam OVER the skin to form a unitized insulation membrane has more effect than the skin by itself… or for that matter, any application of siding put over it when talking about deflecting or absorbing “load forces.”

Now, not just “any old insulation” will accomplish this. Using Rigid insulation won’t do this, and neither will fiberglass batts. It’s the big “glued in” effect of that closed cell foam that does the trick. The foam sticks to everything, in effect making it one big solid sandwich.

Think about NASCAR on the ‘tube.

Using closed cell foam on your container home is like wrapping your container in duct tape. But even then… the dominant benefits aren’t the “implied” massive structural advantages. It’s all about what that glorious insulating foam does for your home in the “comfort and control of mold, water, and vapor” aspects, beyond keeping you warm in winter and cool in summer.

Anyone who tells you otherwise is full of crap.

Your container house is getting it’s strength from the STEEL FRAMING hidden inside it.

Like I said, the REAL benefit to using that closed cell foam is primarily in the vapor and moisture barriers that are created as a by-product of insulating the box to habitable levels, using a quality CLOSED-CELL foam product.

The “big solid load-assisting sandwich” is just a MINOR byproduct, because the frame does most of the work all by itself.

Okay, back to the problem at hand;

Typically, when containers are modified with openings for doors and windows, those openings are “caged” right back in, by making boxes (“welded in – internal framing”) constructed of plate steel (generally 1/4th inch) for those doors and windows to attach to. These new “steel boxes” in the skin would form your “rough opening.”

It’s my position that this would actually serve to reinforce the “skin,” and certainly not weaken it. Look at the photograph up there again… You’ll see exactly what I’m talking about.

Like it carried any load to begin with… (Picture Ronin rolling eyes…)

I suppose you could claim that leaving a small section of Corten skin in place at each end would combat racking. But, I doubt very seriously if a structural engineer could document any difference worth measuring.

I’m betting that the same thing could be accomplished by leaving a “gusset” of Corten steel in each corner.

But, would I do it? No. It’s just absurd. That container isn’t going anywhere near “failureville” because I punched a sliding glass door-set, or some windows into it.

I’ve been building ISBU based Shipping Container Homes since 1977 and I’ve done it on more continents than most people have visited in their lifetimes… (and in some of the most adverse conditions that you can possibly imagine).

I’ve never had ONE fail because I removed a piece of steel skin. NEVER.

Can you challenge their “engineering report/analysis” demand? Can they prove to you that your structure is “unsound” because you cut holes in the skin?

I have never heard of a P&Z Nazi demanding an engineering report for each opening cut into Corten Steel skin on a container, and I’m betting that nobody else has, either.

And it’s not like I’ve only built one or two of these “Corten Castles.” I’ve been building an average of about 3-4 a year, since 1977 (if you average them all out, as  I did take “a few years off” to pursue “some other things”). Anyway…. you do the math.

In fact, the reason I’m doing it again now, for MY family (and several other families), is that it’s the ONLY way  that I believe we’re going to get our families back into  safe, affordable homes before “the world comes to an end in 2012″… 😉

This “request for information” really sounds more like “just driving up the price of your project to make it go away” than anything else to me… They know that making you hire an engineer to give them the numbers is going to be an expensive proposition.

I wonder how these same guys explain “steel skyscrapers” that are basically nothing but girders and glass?  On a much smaller scale, you’re essentially doing the same thing.

So… Is it possible to calculate the engineering numbers yourself? Well, yeah. I guess so.

Your local Library (or local university Library, for sure) will have a copy of “Mark’s Standard Handbook for Mechanical Engineers.”

(Here’s what it will probably look like. It’s one of the copies that  I have. Yeah, I admit it. I have a few. I hate to throw books away.)

If you do any welding or metal fabrication, this book should be on your shelf.

I know… I know… it’s not cheap. But, trust me, it’ll pay for itself.

Depending on what version you can get your hands on… Turn to pages 5-16 (which talks about the “mechanics” of materials), and read thru pages 5-76 where the formulas for calculating stresses of materials are fully explained.

Keep reading… say about 6-12 thru 6-46, and you’ll discover the properties of iron and steel.

If this gets too “heady” (and it certainly can) it’s possible that you could hire a local engineer (in a small shop) to do the math, for $60-75 bucks an hour. (I asked around to establish “average” rates) The fact that you have a shipping container at the heart of your project has nothing to do with these calculations. Just think of it as “corrugated steel welded to Steel Pipe framing.”

I’m betting that it wouldn’t take more than about a day or so to actually come up with the numbers to throw at these fools. But, it’s going to cost you about $500-800 bucks, for nothing. It’s just a waste of time, as even with these numbers, I doubt that they’d know what to do with them.

Gimme a break…

And give them my URL. I’ll be happy to tear them a new… um… er… never mind.

Stay tuned.

Happy Holidays,  You Guys (and Gals)!!

4 Responses to “Container Home Cut-Outs…”

  1. Louise December 21, 2009 at 3:27 pm #

    Thanks for the book tip – I know of a container modifications expert that is trying to lift his engineering game that might like this for his birthday!

    Happy holidays, and a safe and peaceful 2010, to you and your loved ones. Thanks for a great year of blogging, Ronin!


    • renaissanceronin December 23, 2009 at 11:03 am #

      Hey Louise!

      I hope that Santa can find enough sunscreen to head your way, so that you can find something besides rocks in your Christmas Stockings! 😉

      There aren’t many REALLY GOOD texts for this kind of application, but that book is certainly one that should be included in your “reference Real Estate…”

      Watch your email, as well. I have a couple of questions about a post I’m writing about “Container Racing…” 🙂

      You guys take good care of yourself, and have a very Happy Holidays!!


  2. Sean February 2, 2010 at 3:06 pm #

    Hi Ronin,

    To your above ranting, and believe me I know what you are talking about when dealing with the seemingly arbitrary whims of public officials. I am a civil/structural E.I.T. in BC and they never cease to surprise me.
    However I think you underestimate the significance of the skin of the containers them selves. I agree that the main strength comes from the steel frame, it is the combination of the frame and the skin that allows the boxes to be stacked 9 high fully loaded.
    The skin does act as the shear resistence, but it also acts to support the beams and restrain them from buckling failure, so the top beams are fully restrained (continuously connected) in two axis ( the walls and the ceiling/roof). And the skin also keeps the columns and posts vertical again with continuous connection.
    I do agree that minor cut outs and voids being made in the skin will probably not impact the overall strength significantly enough to prohibit the design being passed by the powers that be. But it should be noted that any large span ( as you might have in a five wide ISBU home with a large family room say 20′ opening) should be checked and the appropriate additional section added to ensure safe design. If trusses are being added to get the roof load out to the edges of the buildng the above consideration may be moot, as long as you only remove redundant walls and not load bearing ones.
    Just my two cents, keep up the good work with the blog.



    • renaissanceronin February 2, 2010 at 3:30 pm #

      Hi Sean,

      While I try to downplay the stupidity of building officials trying to discourage construction that they simply don’t understand, I don’t compromise on design engineering, and I’m sure neither do you…

      As an engineer, you already know what I’m about to say, but I’ll do it for those who aren’t “book-leanrt” and field experienced. 😉

      First, in this case, we’re talking about a single story building. The only thing that the container tops are supporting is a SIPs roof, which in this case, almost supports itself. I love SIPs (Structural Insulated Panel) Roofs. Love them, love them… LOVE THEM! 🙂

      I’ve said repeatedly that large open spans must be supported, via truss or column, whether you’re building a traditional home, or one of our ISBU marvels..

      In fact, when building an ISBU home, the steel that you add to “mate” the containers together at each long “seam” assists in that endeavor. When placed side by side, Shipping Containers don’t mate up, rail to rail. There’s a gap between the “walls.” Lot’s of people do it lots of ways, but the way I’ve found to be the most effective is to add steel top and bottom on that seam, to (in effect) turn those top ‘siderails’ into a big tubular steel beam.

      In this case, we don’t even have to worry about that, because several bearing walls in the interior are in place to hold the “roof” up. He’s not building an “aircraft hangar”.

      (Don’t laugh, that’s exactly what some people try to do. They think that you can just hack out all the sides of the containers, and form one great big open room.)

      And I suspect that is exactly what Sean and I are trying to make sure you DON’T do.

      But in this case, the openings that this guy was talking about were for doors and windows in the exterior of the structure. They represent a very small percentage of the Corten Container skin that we’re talking about.

      The loss of shear or lateral force load dispersion is negligible, IN THIS CASE.

      Beyond that, the internal steel frame that is added to actually house the doors and windows (in effect creating the rough opening for them) is going to add FAR more strength than the corrugated steel sheet ever did. It will span from top rail to bottom rail, adding considerable structural integrity to that building.

      When you take something away, you add something back.

      (Sean already knows this, because he’s a Pro. Now, you do, too.) 😉

      My point was that you need to approach this with open eyes, common sense, and diligence.

      Thanks, Sean, for your comment and the clarification!


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