Shipping Container Home Foundation Types Blog Cover

Shipping Container Home: Foundation Types

Posted By: September 2, 2015 In Guides

Want to build your own shipping container home? Start Here.

When constructing a shipping container building, a foundation must be laid for the containers.

Decisions about the foundation type will vary depending on your budget, structural requirements, local soil type, and local building conventions.

Getting this decision wrong can be devastating and it can bring your entire project to an abrupt halt. This is one of the biggest mistakes people make when constructing a container building.

Today we are going to explore the various types of foundations that can be used address the pros and cons of each foundation type.

What Type of Foundation Should I Use?

The two major factors that need to be considered when designing your foundation are cost and what’s required structurally. Let’s address them each point at a time. First, what’s required structurally?

To calculate what is structurally required, consult with a qualified builder or engineer. Just be aware that both your soil type and the number of containers you are planning on using have a large impact here.

If you are constructing on soft soil, then you will need a deep foundation type such as pile foundations.

Whereas, if you’re building on hard soil, you can use minimal foundations. This is because the majority of the weight of the container will be distributed onto the existing hard ground.

Sometimes people prefer to ‘over-spec’ their foundation, which is where you make your foundation stronger than necessary, either for peace of mind or because you prefer that particular style of foundation.

Ultimately though, the decision will revolve around cost, design, and what’s structurally required.

Types of Foundation

Typically, any foundation which is used in traditional home construction can be used for shipping container foundations.

These can be classified into either shallow or deep foundations.

Shallow foundations are laid very near to the ground level, as opposed to deep foundations which can be laid at depths of up to 10 meters.

We are going to focus on the three most commonly used foundations: concrete piers, slab foundation, and piles.

Concrete Piers

Concrete piers are a type of shallow foundation and are one of the simplest and cheapest routes to go.

In their basic form, they are concrete cubes which have reinforced steel within them. Reinforced steel can be either steel bars or a mesh of steel wires used to strengthen the concrete.

Concrete Piers Foundation

Image From Larry

This foundation is definitely the most DIY friendly. It is also the least expensive type of foundation. A great advantage of using this type of foundation is that because the containers are up off the ground it allows for ventilation and prevents condensation forming underneath the container.

Six concrete piers are laid for each container. One pier is laid for each corner of the container and two piers are used in the center to support the middle of the container.

Concrete Piers Foundation 2

Image From Sea Cabin

This is by far the most popular shipping container foundation and is the one we recommend in 8 out of 10 cases.

Slab Foundation

A slab foundation is more time-consuming and more expensive than a pier foundation. It is an exceptionally good foundation to use on softer soil types. If you are going to use a slab foundation, be prepared to dig a lot!

Slab on Grade Foundation

Slab on Grade Foundation

We often see slab foundations used in warmer climates where freezing isn’t a concern. The advantages are that it’s quick and easy to build, and because there are no hollow spaces in the foundation these foundations are less vulnerable to termite infestation.

The disadvantages of a slab foundation are the lack of access to utility lines once the concrete has hardened and the potential for heat loss when ground temperatures drop below the interior temperature.

Pile Foundations

Pile foundations are used when the soil type is too weak to support a concrete base. This type is the most expensive type of foundation covered here.

If you remember, pile foundations were used in the Graceville Container Home Case Study.

Piles (cylindrical solid steel tubes) are hammered into the ground through the soft soil until the piles reach more suitable load bearing ground.

Pile Foundations

Example of Pile Foundations

Once the piles are secured in place they are traditionally capped with a block of concrete. So once you have secured all your piles you end up with a grid system of concrete caps which above ground look visually similar to concrete piers.

Pile foundations are not recommended for a DIY builder. A contractor would be needed to install pile foundations due to the specialist equipment needed, such as the pile driver.

Strength of Concrete to Use for Your Foundation

If you chose to use either a concrete pier or slab foundation, this section is extremely relevant for you.

Once people have decided to use a concrete foundation, their next question is normally about what strength of concrete to use.

The strength of concrete you need to use for your foundation will be primarily decided by the geo-technical engineer’s report.

The concrete strength will be referred to as a C value. C15 concrete, a general all-purpose concrete, is made by using 1 part cement, 2 parts sand, and 5 parts gravel. The higher proportion of cement used, the stronger the concrete. For instance, C30 is very strong concrete made up of 1 part cement, 2 parts sand and 3 parts gravel.

Concrete Pier Foundation Example of Concrete Pier Foundation

If you are mixing small quantities, then you can either do this by hand or by using a cement mixer. For anything more than 1 cubic meter, consider having the concrete delivered directly to your site, ready to use.

Note that, if you are mixing the concrete yourself, make sure you thoroughly mix all the elements together properly, otherwise the strength of the concrete is greatly reduced.

To determine how much concrete you need, just calculate the cubic meters of your foundation. Multiply the width by the height by the depth.

For example, to calculate how much concrete is needed for a 10-foot wide, 22-foot long, 2-foot deep slab foundation, multiply 10 x 22 x 2. The amount of concrete to be ordered would be 440 cubic feet.

Once the cement is mixed with water, it will start to cure. Ensure the concrete cures properly, since this improves its strength and durability. The concrete only cures properly if the concrete’s temperature is kept within a suitable range (refer to the manufacturer’s packaging).

It typically takes from 5-7 days for the concrete to cure. During this time it needs to be kept moist.

Pouring Concrete in Hot Weather

If you are laying concrete in hot weather, it’s crucial you prepare your site correctly before pouring the concrete. Place temporary sun shades up to block any direct sunlight onto the concrete. Also, before you lay the concrete you should spray the ground with cold water. While you are mixing the concrete, make sure you use cold water.

Another good idea is to pour the concrete either later in the evening or first thing in the morning to avoid peak temperatures.

Pouring Concrete in Cold Weather

Like pouring concrete in hot weather, special measures need to be taken when pouring concrete during cold weather.

Cold weather is classed as the average temperature being below freezing for more than three consecutive days.

Before you pour the concrete, make sure any snow or ice has been cleaned from the base and forms. Remove any standing water. Once you have laid your concrete, cover it with insulating blankets right away. Use the blankets for 3-7 days while the concrete is curing. After the concrete has cured, remove the blankets gradually, so the concrete doesn’t crack due to quick temperature change.

Make Your Choice

So hopefully by now you will be able to select the type of foundation you require and also know exactly how to mix the cement for this type of foundation.

Make sure you pay special attention to the advice regarding how to lay in extremely hot and cold climates as this can make or break your container’s foundation.

The next step now is getting your containers delivered and installed on your foundation.


Let us know below it went when laying your foundations!

 

Comments
  1. Dary

    I want to incorporate a basement/solar water storage area under one of my containers. I assume I need to do the digging a few feet from the end foundation piers. Do you have some ideas that will keep this from becoming a debacle? 🙂

    • Tom

      Depends if you want more of a “pit” or a full-size basement that covers the same area as your container. If the former, you need to space the pit several feet away from your piers, depending on soil type and pier design. Loads are transferred through the piers and go into the soil at an angle, sort of like a pyramid. Having the pit within that ‘pyramid’ of soil that is supporting the pier will weaken the pier. If you’re planning to do a full basement, then you’ll basically be setting the contain on top of the basement wall. For basement design, we recommend working with an engineer.

  2. Lilith

    Hi Tom,
    We have an old slab 20 x20 with a crack or two. Would we be able to put 2 20ft long shipping containers on the slab and possibly shim them to level?
    Thank you

    • Tom

      It should be fine. If you shim them, you’re taking load that would have been spread over a larger area (the length of the horizontal and cross beams that are level with the bottom of the corner castings) and concentrating it where your shims are. If your slab isn’t very thick and/or has minimal reinforcement, this could accelerate the cracking. That’s more of an annoyance than a life-safety issue though.

  3. Daved

    Hey Tom,

    I am planning on building a container home in Tampa, Florida. It is not on the coast and not in a flood zone, more inland. Do you know which foundation would be best for that area? Thanks!

    • Tom

      Daved,

      For most cases, we recommend a pier foundation. However, the success of a foundation depends greatly on the soil bearing capacity of the ground in your area, so it’s best to talk with an engineer to verify if it is appropriate. Otherwise, you might experience unequal settling of the corners of your container home.

  4. Arthur Sweany

    Tom, Do you offer your book in print form? I am older and prefer a printed book over downloaded version. If not, how many pages are contained in your e book and would you give written permission to print pages contained within? Thank you, Art Sweany

    • Tom

      Hi Art,

      We are currently in touch with publishers to create a hardback version of the guide later on this year, as the guides are currently eBooks.

      However, we do allow you to print the eBooks if you prefer a physical copy to read.

      Please let me know if you have anymore questions,

      Tom.

  5. Alex

    Hi Tom.

    I am putting up a container on a sloped terrain and would like to mount the container onto a form of gabion as a foundation and i don’t want to disturb the earth too much. (It is in a fossil sensitive area). How would i go about attaching the shipping container to the gabion and would a pile/Pier foundation beneath the gabion work in order to ground the gabion.

    Thanks

    • Tom

      Hi Alex,

      Presumably the gabion will have some form of wirework? I’m thinking one option could be to weld a metal plate underneath this wirework and then weld the container to this?

      Tom.

  6. Tim Senthavisouk

    Hi Tom
    My partner and I are planning to build a storage for 2000 square feet using shipping containers. We have decided on concrete piers and 6 -40-foot high cube. We are in need a set of plan and cost estimate for exterior only. We are thinking of an open plan in which all 6 containers are connected and one entry door.

  7. Shelley

    Hi All,
    Just thought I would share my initial experience with you from here in Elgin Valley, South Africa. I had taken ownership of my containers and placed them on their pier foundations only. I had one 20ft container on top of another and 2 x grounded 20ft containers alongside. Winds of 140kph sent the 2 containers that were top and bottom off down my small holding and blew one of the grounded 20ft containers over onto it’s side!!
    Moral of the story……bolt your containers down. Even a strong gust can send them rolling 🙁

    • Tom

      I’m sorry to hear about this Shelley.

      Can I ask why they weren’t bolted down immediately after they were sited?

      Tom

  8. Kevin McMahon

    Re:Tornado Country Question. I know that a twistlock base Welded to a square steel base plate) can be bolted to the top of a pier using Ramset or pre-cast bolts. But how deep would these bolts have to penetrate the concrete pier to be an effective anchor in Cyclonic conditions? Isn’t there a danger of the top of the concrete simply being ripped off the pier? I am trying to over-engineer a better solution.

    • Tom

      Hi Kevin,

      It depends on the type of foundation you’re using, the connection to the plates and also how many fixings/bolts you’re planning to use.

      Let me know,

      Tom

  9. Russ

    Is it possible to join two 20′ side by side, and cut out the fronts and interiors to create one 16×20 foot structure? Think of a garage that would accommodate a car.
    I assume square framing would be required in front,middle,back to pull this off.

    Thanks!

    • Tom

      Yes Russ this is certainly possible but as your mentioned, framing and support would be required.

      Tom

  10. Wendy Miller

    My question is on pillar supports.

    If all the weight of the container is in the four reinforced corners what is the purpose of the 2 middle pillars? The container is supported from corner to corner by 1 length of steel so it would seem to be that the middle supports are redundant.

    • Tom

      Hi Wendy,

      It depends on the containers. I generally recommend the 6 pillar approach for 40ft containers. The middle supports should be set slightly higher so they reach the centre of the container.

      Tom

  11. Francois

    One type of foundation which I do not see being covered here is the perimeter wall type which is almost like a traditional foundation (at least for us here in South Africa).
    With regards to the pier type of foundation, it seems the most cost effective…but my concern is what about insects and weeds that grow just about anywhere…what is your experience with that?

  12. Ishty

    Hi Tom,
    I’d like to build container bungalows from 2x20HC containers close to a sandy beach in the tropical cyclone zone. Are concrete piles in the corners the best solution if I want to raise them 1m above ground,please? I was wondering if you could recommend the size and depth of concrete piles that I would need to use. Thanks!

    • Tom

      Hi Ishty,

      Without inspecting the site in person I can’t advise you sorry. However if you send me some photos I might be able to give you an indication…

      Tom

  13. John

    While the 10 x 22 x 2 = 440 CF calc is correct, it misses the fact that concrete is ordered in cubic yards (meters), so you would need to divide by 27 and order 16.3 yards, and round up so that you are sure you have enough. Hopefully, you can order whole truckloads, or pay a premium for a partial load.

    • Tom

      Thanks for adding this John.

      You’re right- in certain countries you will need to order concrete in cubic yards rather than foot 🙂

      Tom

  14. Prateek

    hey
    I’d like to build my container home on a hill and there is colder climate.
    So, what type of foundation should i use?
    can i use Concrete Piers?

    • Tom

      Hi Prateek,

      Without seeing the site you plan to build on, it’s hard to say. If you send me an email with some photos I will be able to better help you,

      Tom

  15. Mario

    More of a question. I’d like to build my container home on a farm in central Missouri which is in tornado country. I’ve been thinking of two options: a forty by eight for container or a 20 by 8 foot with a storm basement that doubles as a bedroom. Which type of foundation do you recommend to withstand a tornado for the container. Also, do I need to do anything special to cut a whole in the floor for stairs to go to a basement. I’m already planning on a steel beam by the ceiling for support in order to remove most of the front of the container for glass and sliding or French doors. Thanks. I look forward to your posts.

    • Tom

      Hi Mario,

      I’ve not looked at foundations specifically for tornados, so I’m not sure how much help I will be.

      However clearly the containers would need bolting down, so an extremely strong concrete base would be needed and then you can bolt and weld the container in place.

      Tom

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