how thick is a wall?

I am moving forward with setting up my shipping container to live in temporarily. Before it leaves the sellers I'm going to have him do some welding and cutting.  I want to plan ahead a bit. Later I will build a wall with a single  door and maybe a window inside the short end of the container. Then I will be able to close the container doors over that wall and lock it when I am gone for extended periods.  It will be 2x4 construction. I am insulating the rest of the container on the exterior and using a cement fiberboard as the final layer. I will use the same fiberboard on the exterior of this wall. The interior of this wall will be a simple wood shiplap. The question is, how thick will this wall be? I was thinking of having him weld tabs inside as bracing for the wall so that I don't have to pierce the container, so I need to tell him where to put the tabs. Or perhaps there is a simpler or better way to do this?

Oops, not shiplap but tongue and groove or something that is real wood, not an engineered wood or pressboard or OSB or plywood.

Typical wall, from inside to outside, is:

Drywall (1/2) + stud (3 1/2) + sheathing (1/2) + siding (?)

If you siding comes in 4x8 sheets, it can count as the sheathing.

Ship lap can be 3/8 to 3/4

The thickest thing is probably the door trim.  Standard brick mold is 1 1/4 to 1 1/2 thick.

If you put your tabs so they clear the inside of the door by 2 inches, they should work fine if they are used on the outside of the studs.

Denise:

Glad to see the project is moving along!

The wall thickness depends on construction method.  2x4 is 3.5".  Frequently there is a layer of OSB/Ply over the 2x4s, generally about a 1/2".  But not necessarily.  Sometimes there is board insulation as well, and that's of varying thickness.  And finally there is the cement fiberboard, which is probably 1/4" thick and thus comes out just over 1/2" when lapped.  And the interior ... you'll have a vapor barrier (negligible thickness) and then the inerior t&G - probably 1/2".

So ... the OSB/plywood exterior does two things  - it really stiffens the assembly  (probably not critical in this instance!), it also provides a good backer/foundation for the cement board (cement siding is brittle  - without a backer it can easily collapse if a knee or pot or hammer thrown in disgust hits it).  Finally it does a really good job of air sealing the whole thing. I'm going to say you want it, and will use the 1/2" variety.

So #2 ... exterior board insulation.  Often a nasty foam, but possibly rockwool board or corkboard, this really increases your R value.  Or you can make the wall 2x6.  Adding 1" of rigid insulation adds another r7 (I think...), adding two inches to the studs does about the same.  Your call.

So 3.5+.5+.5+.5= 5" before board insulation or 2x6 bump.

That said, I'm worried about your insulation plan.  If the whole exterior is covered and insulated ... except this one end which has internal insulation ... then ALL of that metal on the inside suddenly has a thermal path to the outside heat/cold and bypasses the insulation.  The other problem is that if the walls are insulated up to the doors, then the doors can only swing to a max of 180 degrees (not 270) so they will stick out like big ears and can't be folded against the sides.  Or you have 4' of exposed metal on each side.

Eliott Mason, I wish I had spoken to you at the beginning of my whole thought process which started a long time ago. As much as I thought about insulation I never considered that that short wall would cause a thermal bridge. :0(
I do realize the doors won't fold back all the way and I don't mind ear flap doors. I will use the doors to protect this entryway from the sun and the wind .
Any thoughts about how to get around the thermal bridging?

denise ra wrote:Eliott Mason, I wish I had spoken to you at the beginning of my whole thought process which started a long time ago. As much as I thought about insulation I never considered that that short wall would cause a thermal bridge. :0(
I do realize the doors won't fold back all the way and I don't mind ear flap doors. I will use the doors to protect this entryway from the sun and the wind .
Any thoughts about how to get around the thermal bridging?

I don't see any easy answer, yet... the hard way would be, remove the doors, frame your wall on the outside, completely enclosing the container by joining wall insulation directly to the other external insulation...

Then have new mounting points fabricated for the outer side of this wall and install the container doors there.

Those doors are damned heavy, the wall will need to be built with this in mind...


The result would be excellent, but definitely some cost/hassle involved...

For that matter, if you are redoing the doors... you could build an enclosed but uninsulated porch area with roof and heavy duty side walls, and mount the container doors onto that...

D Nikolls, thats way too rich for my blood. :0)

Ya, I wouldn't much like to pay for it either... and I would be nervous about DIYing the attachment setup directly to the wall. I think the easiest would be the doors-mounted-to-porch version, but it would sure be a hassle... speaking as someone with a tractor and a welder..

You could simply ditch the doors.. annoying.

You could build say 6' of additional space onto the front, completely enclosing the doors but keeping them as an internal divider; anyone breaking in would have access to only a few feet of space with getting a grinder or torch involved...

Would not be helpful for later mobility of the seacan.. tradeoffs.


Hope someone else has a better idea!

D is right about one approach ... and I think is in agreement that that's not an ideal approach.

I totally understand the appeal of closing up that end with those beefy beefy doors and going away without a worry.  Although I would caution that those doors are still only as good as the lock, and folks who buy these for secure storage on construction sites have giant after-market additions to keep locks from being tampered with (e.g. https://www.mobilemini.com/product-features).  Which is to say that you may find as much security in shutters that you place over the door and window... and if you have any windows elsewhere cut into this (please do ... emergency egress if nothing else) then whatever shutter system you have there is the weak link in your security chain.

Thus I'd suggest continuing your external layer just past the end of the container (basically just a 2x4 or 2x6 past) and then build the end wall there.  Remove the doors.  No welded tabs required.

I agree with Eliot - if the end was the only opening in the container, keeping the doors would be a reasonable security measure along with a serious lock setup. As soon as you have other windows, especially ones good enough for emergency egress which you should have, the steel doors become irrelevant. I would remove them and build the insulated wall around the whole end. The doors might be useful as a porch roof.

I suppose we are talking extreme thermal bridging with my original idea?

The only other opening is a double french glass door that's going in one of the long sides. My welder was going to make a door/shutter out of the part he cut out and use it to secure the French doors. Besides vandalism I'm also would like to be able to lock myself in in tornado weather.

denise ra wrote:I suppose we are talking extreme thermal bridging with my original idea?

The only other opening is a double french glass door that's going in one of the long sides. My welder was going to make a door/shutter out of the part he cut out and use it to secure the French doors. Besides vandalism I'm also would like to be able to lock myself in in tornado weather.

Well... you could put in a normal-sized man-door at the non-door end of the can, have him do a shutter the same way, and simply seal over the main doors...

I really like the idea of shutters, especially in tornado country...

Thanks to D and Glenn for helping to crowdsource a solution!

The thermal bridge problem ... I'm not sure HOW big it is.  But given the interior is all steel, its basically a giant heat wick.  Some people with the right software could figure out the equivalent clear opening (e.g. the equivalent open window size), but let's just say that it could make one end of this uncomfortable!  Especially during the worst temperatures when you have a high delta-T... when its 20 degrees outside the heat is absolutely going to flee your little abode!  Imagine your heat source/wood stove was built into the wall and exposed to the outside ... something like 32 sq ft (more if we counted the heat lose through the hinges to the doors) of just trying to heat the outdoors.

I like tornado proof and applaud the idea of a shutter (although I'd prefer a larger shutter than the door... so using the cut out piece is less effective as if the wind gets under an exposed edge you may not have a shutter!).  I'm afraid I'll also point out that you're putting the softest bits on the outside (siding and insulation) where they are simply ablative to a tornado.  But interior space ....

I'm sorry if I'm starting over ... if you insulate on the interior then your exterior door works.  You'll lose interior volume but you'll have a nicer looking interior (quieter too) and you won't lose the functional benefits of a container.

Another question ... how are you going to insulate the bottom of the container?

D Nicholls- you are smart!! I spent so much time on this project, it's hard for me too adjust my thinking.

There are a number of reasons to insulate on the outside: 1. it is a hundred degrees here for three and a half months of the year. 2. Exterior siding and a roof add to my missile protection factor from tornadoes. 3. I'm sensitive to chemicals that might be used as insulation such as spray foam, or that must be used to glue insulation and spray foam fill the gaps for InSoFast for containers.

Since y'all are being so helpful maybe you can help me with my other problem which is I have a set of out-swing double French doors that I want to put on one of the long sides. I don't know how to detail exterior insulation and siding for those French doors and it seems I would have to build out around them in order to put a shutter over them. I'm about ready to sell them at a loss and switch to in-swing. Besides the door and window on the short end these were to be my only other egress.

If you don't want it to look like a container from the outside, the cost of weatherproof siding is one you would need to bear anyway. Likewise, you will want some finish material beside steel on the inside so it doesn't feel like a tin can. Given the total vapor impermeability of steel, you are probably best off in a cold climate having that on the inside of the wall assembly. On the outside it would trap whatever vapor made it through and condense it with no way of escape.

I can see keeping the doors operational for tornado resistance. Your welder can fabricate standoff hinges for the French door shutter(s) so that they can fold flat against the wall when open.

The thermal bridging issue could be mitigated by adding say a foot of insulated wall along the inside of the container sides so that heat has to travel a foot along the steel before reaching the exterior. This would not take much away from usable interior space.

Do you have a plan for roof configuration yet? I would presume if you are adding exterior walls you would have to have roofing on top of the container to keep the walls dry as well as give space for insulation. As long as the roof framing is locked to the walls and/or the container itself you should have no problem with structural integrity.

Outswinging French doors add some trickiness to the situation. I think there is not a practical way to allow those to fold flat against the wall when open while having insulated exterior walls and storm shutters. I would set up stops on the porch/deck you will presumably have outside to keep the doors from damaging their hinges. There are numerous ways you could do that, and I would not try to suggest the best method without a lot more detail of the actual construction. Some kind of folding braces mounted on the inside of the storm shutters, which fold flat when you want to close the shutters, might be the simplest.

Regarding heat, it sounds like some roof overhang is mandatory for shading the walls so they don't turn into radiators on the inside. Maybe light (folding?) screens or awnings would be safest? Maybe you set up an awning/canopy over the whole container, with the understanding that the fabric is sacrificial in a tornado situation? That would keep the whole roof shaded and ventilated.

Perhaps the French doors go at the end of the Can, to be covered by Can doors when stormy? Then revert to a slider or regular door where the French doors were planned?

Do think long and hard about thermal issues and condensation NOW...even breathing and cooking (and cleaning, bathing, even some heat sources) produce water vapor. Without the thermal break, all this will condense on the inside and freeze or drip/run down from walls and ceilings. There will have to be some sort of fan, to move air and some sort of moisture extraction mechanism to avoid damp and mold.

If in fact this will also be a storm shelter, do give serious thought to how it will be anchored (partially buried?) so it cannot become a giant metal tumbleweed. This would likely involve earthworks or concrete, and likely not be kind to your budget, but a VERY prudent move. If in fact you COULD earth bury it (at rear) that would help significantly reduce insulation and exterior cladding costs - a tradeoff that might well pay for itself.

Full height berming/burial on one side of the container will give it stresses it was not built to take. I could see making a berm along the back with several feet of clearance, and roofing over the space to give shelter to the container and a dry storage corridor. It wouldn't actually anchor the container much, but it would definitely reduce its exposure to wind loads. Then you just need to concentrate on strong anchors for the front side.

Glenn wrote "The thermal bridging issue could be mitigated by adding say a foot of insulated wall along the inside of the container sides so that heat has to travel a foot along the steel before reaching the exterior. This would not take much away from usable interior space. "
I was wondering about this, thinking if I went six feet it might for all effects and purposes solve the problem.
As to offset hinges, would that be for the French door and for the shutter? Each would have offset hinges?

Sorry my replies are so awkward but I'm doing this on my phone.
The plan is for a shed roof which will protect the walls. Not much overhang though to reduce uplift. Glenn I'm not sure what you mean by folding braces. A shade over the container would be great but I wonder if a fabric shade can be stretched enough not to flap? The wind blows 20 mph all day at least a couple of days a week here. I will weld it to concrete Piers which are sunk in the ground, I'm looking for an engineer as we speak. To allow for ventilation I'm thinking about a Panasonic whisper quiet or whisper light ERV. Because air conditioners only recycle the indoor air they don't bring in fresh air.

I think if you have a smooth curved frame for the canopy it would flap less or not at all. Getting a shop to bend pipe in a 20' radius may be reasonable. About 12' long would give you a couple of feet overhang on the south side (none really needed on the north side.) I think you could attach the frame to the container, as long as the canopy (or its edge lacing) is not so strong that it would act as a sail in catastrophic winds.

I'm not sure it would be practical to make offset hinges for both shutters and French doors. The braces I envision would maybe be hinged from the hinge edge of the shutters and fold out to stop the doors without hitting their glass, at the widest opening the doors are capable of without stressing their hinges. They would have some sort of sliding or collapsible strut going back to the middle of the shutters to support them. Maybe they would have hooks on the ends to hold the doors open when you want them open.

Denise, Here's an idea to solve both the thermal bridging and the fastening of the wooden end wall behind the metal doors: Cut the walls and ceiling on the centerline of where the wooden wall will be. You will drastically reduce the bridging, since only the floor and corners of the container would still be connected.

There's many ways you could accomplish this, here's two:

Have the seller weld some steel angle to the walls and ceiling, spaced 3-1/2" apart (in the position you want), so that you can bolt/screw a 2x4 (or 4x4) in the space between them. When you build your wall on-site, you will fasten it to these 2x4s all around (and the floor as well), and the angles will be covered up by your sheathing and finish carpentry inside.
Once the 2x4 is installed between the angles, but BEFORE you work on the outside insulation and sheathing (so you can get to it), use an angle grinder and a cut-off wheel to cut the wall and ceiling panels of the container where the 2x4 is. You won't cut through the corners, and you could skip a couple of 2-3" tabs on each wall/ceiling to keep some attachment intact if you want.

Wait until you are on-site, cut the walls/ceiling as above, and bolt through the wall/ceiling and two boards/plywood (one inside, one outside). Your wall attaches to these boards inside as above, and the outside board is either hidden by or is part of your insulation and sheathing plan.

Kenneth Elwell, now that is thinking outside the norm. I like the angle iron idea too.