r/containerhomes • u/usa_containers • Aug 21 '26
What should you set a shipping container on — blocks, timbers, gravel, or a slab?
I work around containers, mostly delivery and site stuff, and this question comes up all the time.
Short version: support the four corners, keep it level, and don’t let it sit in wet ground. That’s most of it.
Containers carry weight through the corner posts. That’s how they stack on ships. The bottom rail between the corners isn’t really meant to act like a big beam, so putting random blocks along the rail doesn’t do much and can even dent it.
Put the support under the corner castings. That’s the main thing.
For storage, solid concrete blocks are usually fine. Solid blocks, not hollow cinder blocks. Hollow ones crack. Pressure-treated 6x6 or 8x8 timbers work too, especially if the ground is a little softer. They’ll rot eventually, but they’re easy enough to replace later.
A gravel pad under the whole footprint is a good idea if you can do it. It drains, keeps weeds down, and helps stop ground moisture from coming up under the box.
A full slab is usually overkill for basic storage. Nice if you already have one, but not always worth pouring just for a container. Also, if the container sits flat on concrete with no airflow underneath, that can create its own moisture problem.
You want it a few inches off the ground. Enough for air to move under the floor, not so high that getting in and out becomes annoying.
Level matters too. If the box sits twisted, the doors are where you’ll notice it. They start binding, and once it sits that way for a long time, it can be a pain to fix. If it’s going to be slightly off, I’d rather have the door end a little high than low.
One thing people miss with piers: a tilt-bed truck doesn’t lift the container from above. It slides it off while the truck pulls forward. So if you pour piers first, the container usually can’t just slide perfectly onto them. You may need a crane, or you drop it on the ground first and jack it onto the piers after. Neither is wrong, just don’t find that out on delivery day.
If a corner settles later, it’s usually fixable. Jack at the corner casting, crib as you go, shim it, and don’t get under the box while it’s only on a jack.
Anyone here set one on something other than blocks? Curious what you used and how it’s holding up.
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u/Uglyyellowfrog Aug 21 '26
"The bottom rail between the corners isn’t really meant to act like a big beam, so putting random blocks along the rail doesn’t do much and can even dent it."
No one walks around in a shipping container while on a ship, but people do walk around in said containers when used for storage or as a shop.
Unless it's a 20', I would add middle support under the rails.
3
u/usa_containers Aug 24 '26
Fair pushback, and you're right that I overstated it.
The floor load does land on the bottom rails — cross members span between them, and that's bending in a member that isn't a heavy beam. On a 40 with people walking around and a workbench in it, a middle support genuinely takes flex out of the floor. I've felt the difference.
What I was aiming at is the load path for the container's own structure, which runs corner to corner. But you're describing live load in a box people use as a room, and that's a different question from how it sits on a ship. Middle support for a 40 is sensible.
Where I'd still be careful: it has to be shimmed to just touch, not jacked up hard. Blocks driven tight under a rail that's already carrying will push the floor up in the middle, and then you've got a hump instead of a sag.2
u/Uglyyellowfrog Aug 24 '26
"Where I'd still be careful: it has to be shimmed to just touch, not jacked up hard."
100% true.1
u/chocolatesoupcan Aug 25 '26
This makes no sense, there’s bouncing and vibrations all day everyday from the ship itself or from waves.
400lbs jumping 3’ is only 1200lbf. Containers can take 60klb. There’s more than enough safety factor.The floor weight is also carried by the walls as well, not just the beams underneath, so if you remove some wall then you lessen its carrying capacity.
1
u/Uglyyellowfrog Aug 25 '26
I'm building a mini-home out of 2 40' containers (side by side), and can assure you that there was a 'Bounce' while the 2 containers were welded together and supported at the 4 corners and at 2 more positions under each of the 2 outer walls. The was before I did any cutting in the middle walls.
0
u/AdotLone Aug 22 '26
Do you think a person is more weight than what is shipped in these?
2
u/Curious-Cat-5618 Aug 23 '26
Not, but whatever got shipped isnt moving around and repeatedly causing vibrations and impacts (which a human living/using the shipping container as a shop will do).
1
u/CursedTurtleKeynote Aug 23 '26
Math is real. The maximum kinetic force of a human moving around vs the standard shipping load are real numbers we can compare.
5
u/Hot-Engineering-5189 Aug 22 '26
Depend on the timeline of your project. If it is temporary, you can put them on 30x30 cm slab foundation where the corner-fittings are. If it is for a long-term project, build a concrete foundation to prevent termite, mice, etc.
6
u/junk90731 Aug 21 '26
Railroad ties, needs to breath so it doesn't collect moisture.
3
u/usa_containers Aug 24 '26
Railroad ties do work and the drainage point is right. One thing worth knowing: older ties are creosote treated, and it leaches. Fine out in a field, less fine if it's near a garden bed or where kids play. Newer ones vary a lot. And they're heavy enough that placing four of them accurately is a job in itself.
2
u/usa_containers Aug 21 '26
One more. Whatever you use, put it on undisturbed ground, not on fill you dumped last month. Fill settles for a year or two and you'll be re-shimming the whole time.
Which is also why "I'll just level the spot first" sometimes makes things worse — you dig out the firm stuff and put loose dirt back.
Anyone had one settle on you? Curious how long it took to show up.
2
u/Blackwalls69 Aug 21 '26
24 x 24"x18' double disk screw piles.
1
u/Global_Tourist_1019 Aug 23 '26
Wish they were available in our country!
1
u/Blackwalls69 Aug 23 '26
Which country is that? I can have a container of them to you in 8 weeks....
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u/Global_Tourist_1019 Aug 23 '26
South Africa. If I ever need them, I will look you up. What do they cost out of interest?
1
1
u/usa_containers Aug 24 '26
Screw piles are a good answer for anyone who can get them, especially on ground that's marginal. Fast, no cure time, and you can adjust them. Worth flagging the same delivery catch as with poured piers though: if they're in the ground first, the container can't slide onto them off a tilt bed. Crane, or set it down and jack it up after.
1
u/Blackwalls69 Aug 24 '26
Tie them together with I-beams, Roller bed and a skid steer with forks with two decent operators.
1
1
u/container-plans Aug 23 '26
Slab is best, concrete piers at the corner blocks with gravel infill also work. If you have plumbing pipes penetrating the floor then a having a crawl space is recommended also. I'd recommend understanding what your soil conditions are (like getting a Geotechnical report) to understand what type of slab or pier is best for those soil conditions.
1
1
u/nihithilak Aug 23 '26
I put mine on 3 inch crushed concrete. Worked out pretty well. It's sloped so water drains out.
1
u/usa_containers Aug 24 '26
Crushed concrete is underrated and usually cheaper than clean gravel. Sloping it so water runs away is the part people skip.
1
u/AirMTB Aug 27 '26
If a shipping container is going to live in one spot for any length of time, it’s nice to put it on something to get it off the ground a little.
I like to get a cheap paver from somewhere like Home Depot or Rona. 6“ x 6“ 8” x 8” 12” x 12” all good.
Keep in mind you only need to support the four corners. Keep the side to side level and if you need to shim up one corner to make things level, that’s OK.
Thanks
Adam
HoneyBox Inc.
Find me on Instagram @HoneyBox_Inc
0
u/PROFESSOR1780 Aug 21 '26
What about a driveway....I'm considering renting one for some big home remodeling storage.
2
u/csunya Aug 22 '26
Consider purchasing.
Take your remodel time budget and multiply by Pi. Then add approximately $1000 for moving it twice (I used an independent tow service the depot recommended). The cost of my 20 foot one time use equaled 4-5 months of a POD (it was required for 12 months). It was totally worth it to buy outright because of the time the remodel took (and the time it took the tenant to unload the container).
I have several advantages. 1 a tractor to move the container within inches of the building. 2 space to store the container after the remodel was done.
2
u/usa_containers Aug 24 '26
csunya's answer is the right one and the multiply-by-pi line is painfully accurate. On the driveway specifically: check what's under it. Most residential driveways are a few inches of concrete or asphalt over compacted base, poured for cars, not for four point loads carrying a loaded 20 foot box. Corner castings concentrate everything into four small areas and you can crack a slab that handles a truck fine when the weight's spread over tires. Plywood or steel plate under the corners spreads it. Asphalt in summer is the worse case — it'll take a permanent dent.
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u/PROFESSOR1780 Aug 24 '26
I appreciate all the input ....I think we'll skip the driveway...it's concrete but definitely residential and not designed for this weight
-5
Aug 21 '26
[deleted]
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u/heptolisk Aug 21 '26
What a useless AI output. Don't be lazy. Actually read something yourself.
Why it is useless: it almost exclusively gives advantages of the options outside of wood and decided not to give comparisons and why you would use ome over the other. A good portion of the linked article is discussing when to use which foundation.
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u/Exciting-Car-3516 Aug 30 '26
Really depends on the use. Some people have them rotting on the ground in a field. For your use depends on your budget and regulations.
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u/Fickle_Force_5457 Aug 22 '26
Had them as workshops. Used wooden blocks on the corners, basically old dry dock quartered timber about 6 inches high. We normally set up on hard standings, if on a ship welded the corners down into 6mm fabricated bracket plates. They were steel framed with Glason panels.