Do I Need A Foundation For My Shipping Containers?
So before we look at the various types of foundations you can use for your shipping container home, lets first look at if you actually need a foundation.
In short, you will always need a foundation for your shipping container home.
Unfortunately, the ground beneath us moves a considerable amount; it can rise, sink or slide. This movement is sporadic and is hardly noticeable but this slight movement will make a huge difference to the level of your home.
A foundation provides a solid stable platform from which you can build on. Without this solid platform the ground’s natural movement can twist and cause the containers to split and separate.
Not only does the ground underneath your home move but it can also be comprised of different materials. For example, part of the ground could be hard rock and the other part soft clay. This creates an imbalance which again can twist and move your home, as the load isn’t equally distributed.
A solid, well built, foundation will ensure the weight is appropriately distributed throughout each corner of the container(s). It will also help prevent moisture and the corrosion as a result of this moisture.
Finally, without a foundation, the doors on un-level containers are incredibly difficult to open and close, which isn’t ideal!
If you’re shipping container home is temporary and will only be left in a certain place for a few months then you don’t need significant foundations- railroad ties (also known as sleepers) will do.
However if you’re planning on a permanent dwelling a more long term solution is needed.
With that being said, let’s now take a look at some common foundation types which can be used for your shipping container home.
Types of Shipping Container Home Foundations
In my experience there are three main foundation types which can be used with container homes: pier, slab and strip.
I will now go through each of them in turn and outline when you should use each one and the strength and weaknesses for each of them.
Pier foundations are the most popular choice for shipping container homes for numerous reasons: they are cheap, DIY friendly and quick to construct. But before I get ahead of myself let’s look at exactly what a pier foundation is.
As seen in the photo above, a pier foundation is comprised of concrete blocks. Each concrete block (pier) is generally 50cm X 50cm X 50cm, but obviously this can vary significantly depending on the build.
With shipping container homes, the concrete piers are generally laid at each corner of the container- and with larger 40ft containers, an additional two piers are placed halfway down each side of the container.
The pier foundation is a favorite amongst all DIY home builders because they are the simplest, cheapest and quickest foundation to lay.
You save a lot of time and money with pier foundations because you don’t need to excavate a lot of earth at all.
You only need to excavate the ground for the piers, which are generally 50cm X 50cm X 50cm. Compare this to a slab foundation where you will need to excavate more than 18ftx18ft.
Another great reason to use a pier foundation is that other foundations, such as pile foundations, require expensive specialist equipment which can obviously be inhibitive for DIY builders and hobbyist.
Whereas for pier foundations all you need is the humble spade.
A slab foundation, also known as a raft foundation, is a popular choice when the ground is soft and requires an equal weight distribution.
As shown in the photo above, a slab foundation is as it sounds- a concrete slab which your containers can then be placed onto.
The slab foundation is generally slightly larger than the footprint of your home.
So if you’re building with two 40ft shipping containers your slab foundation would generally be 18ft wide by 42ft long. This would provide an overhanging foot of foundation around the perimeter of your shipping containers.
This type of foundation is generally used on softer soil types. Pier foundations place a great amount of load under a small surface area whereas slab foundations spread the load across a large surface area.
A huge benefit of slab foundations is that because it provides a solid base, there is no hollow space in the foundation. This prevents future problems such as termite infestations.
Unfortunately though, because of the additional concrete used and the vast amount of space which needs excavating, slab foundations are significantly more expensive than pier foundations.
Also once the concrete has set, there is a lack of access to utility lines. For instance, if you have a leak in your water pipe you will need to cut out the concrete to access the pipe. Whereas with a pier foundation, you will always have access to your utility lines.
A strip foundation (also known as a trench foundation) is somewhat of a combination of the previously mentioned pier and slab foundation.
The strip foundation (as shown below) is simply a strip of concrete which is laid to support the containers. The concrete strip is normally 1-2 foot wide and 4 foot deep.
The strip can either go around the perimeter of the containers or it can be laid at the top and bottom of the containers instead.
It’s ideal to use when you’re looking for a cheaper alternative to the slab foundation but have slightly firmer ground to lay the foundation on.
It’s also a great foundation choice when the ground is damp and liable to lots of water. You can use a rubble strip foundation which uses loose stone below the concrete strip. This stone allows the water to run through and drain away.
Like all the foundation types mentioned, strip foundations also have their weaknesses. For instance strip foundations have a weak resistance to wind and earthquakes. Also, due to their shallow nature they are only suited for small and medium sized builds.
How to Fix Shipping Containers to Foundations
Now we’ve been through the most popular shipping container foundations, let’s look at how to fix the containers down into the foundation.
The most popular way to fix containers to the foundation pad is through a steel plate which has been set in the concrete.
Whilst the concrete is still curing, you can set down into it a steel plate with vertical bars that sink into the wet concrete.
Paul Chamber’s video shows an excellent example of this.
Then once the concrete has cured you can place your containers on the steel plate and weld them together.
If you don’t want to use the steel plate technique outlined above, instead you can bolt the containers down into the concrete using concrete anchors. This is a simpler technique but the hold isn’t as strong as welding the containers.
Finally, if you’re opposed to fixing the containers down, you can just place the containers onto the foundations; however I always prefer to fix them down for additional strength.
The only exception being if you want to make your shipping container home portable.
After reading this article you should be much more comfortable with shipping container home foundations and know which one is appropriate for your particular setting.
It’s also important here to say that there are many more types of foundation which haven’t been discussed here.