There are different types of foundations that can be considered for shipping container builds. These range from the cheaper ones to the more expensive options. For this project, I have used solid concrete pillars to support the shipping containers. This was built in agricultural land, in south India, specifically a coffee plantation in Coorg, Karnataka, which had soft soil.
Why use a concrete pillar foundation?
- The main weight bearing points of the 20ft shipping container are at the 4 corners. This is how many of these are stacked on top of each other on the ships.
- Allows you to easily change into a more conventional brick and mortar structure, if you plan on moving or selling the containers.
- Raises the height of the entire structure and gives it more visual presence, useful in a commercial shop setup.
- Solid pillars ensure a level, strong surface in softer ground compositions like agricultural plantations.
- Improves longevity and protection from rust as water will not stagnate around the base.
- Prevents rodents from burrowing through the original plywood floor board of the container, especially in setups with food storage.
Concrete foundation
The concrete foundation included 6 pillars for each container, with a smooth cement platform finish on the underside. 2 of the middle pillars are redundant for supporting 20ft containers. Each of these pillars required digging a square pit 4ft*4ft about 3ft deep. The height of the pillars from the ground level was to be 2ft.
Inside these pits, are placed steel rod pillar frames. The frames were made with 10mm gauge for the long sections and 8mm for the horizontal grid section. The length for each of the 4 vertical sections of the pillar can be approximated to 6 ft where 1 ft is the base section extending outwards from the corner, 3 ft to reach the ground level, and 2 ft height above the ground.
The concrete mix used was approximately 1:1:3 cement, jelly, and sand.
Practically, 1 bag of cement is mixed with 6 bandli’s of sand (MSand in my case) and 2 bandli’s of jelly. Water is added and mixed to get the right consistency. This is with the assumption that 1 bag of cement can be poured into 2 bandli’s. Please check and confirm in your own use case. Also, while mixing larger quantities, the ratio of cement to jelly used was 7:8.
A ‘bandli’ is a wide plastic bucket used for manually moving sand and jelly from one place to another, and also to measure these parts to mix with cement. This is then poured into the pillar cast.
The pillars are spaced so that the profile of the container fits directly over it, with an additional half inch on edge sides. This makes the setup look sleeker than if the measurements of the container profile were to the centres of each pillar.
The space around the pillar is filled with boulders only under the container profile, and the remaining space is filled with mud.
After the pillar areas have been filled, the top layer of ‘boulders’ is laid along with 6 inch jelly, so that a smooth cement finish can be done over it. This smooth finish adds aesthetic appeal and serves to keep away growth of weeds. A traditional brick and mortar structure can later be built upon this if needed.
Boulders are big size rocks, while jelly is smaller. The jelly used for the smooth surface finish under the container is 6 inches whereas the type used for casting the pillars were 1-2 inches. The big boulders can be hammered manually to make smaller 6 inch jelly pieces, but may not be as uniform.
Cement is added to make an even surface and a top smooth layer is made. Since it was raining, a shamiyana was covering the surface to avoid droplet spots. It is left to set for a day.
Tarp to prevent rain from spoiling finish 
Conclusion
Overall, to get the foundation for the container ready, it took about 1 – 1.5 months, where rain played a part in the efficiency of labour. This was around July-August in South Coorg. I worked with a local contractor who apart from assisting with technical know-how, also co-ordinated sourcing of material and arranged workers. The work involved marking the layout, digging pillar holes, setting of pillars, filling the foundation and making a smooth floor surface.
I had absolutely no clue about construction but was excited about learning. The overarching agenda of this project was to build it fast, at minimal cost, with a novel appeal. The DIY (do-it-yourself) vibe of shipping container builds, and the implied money saving aspects, got me interested in taking this on as a personal project.
I learnt many things along the way and I hope you find some of this content useful for your own builds. The internet is a source of infinite subjective wisdom which I tap into for researching about things, and this is a way to give back to this wonderful environment.
Coming soon..
Knowing the estimated cost of materials and labour can be useful decision points for planning a shipping container build. It is not as cheap and simple as you think. Stay tuned!
Please post a comment if you have some specific area you would like me to talk about and I will consider doing it.
