Before your container arrives, your foundation needs to be ready and fully cured. Here’s exactly what we use, why we use it, and the one planning mistake that sets builds back by weeks.
Of all the steps in a container home build, the foundation is the one you absolutely cannot rush. Concrete takes 2–3 weeks to cure properly before it can bear the weight of a steel container. If you order your container before your foundation is ready, you’re paying crane and backhoe operators to wait — or you’re placing your home on soft ground and moving it again later. Neither is a good option.
We’ve built container home foundations on all kinds of properties here in Costa Rica — steep jungle lots, beachfront plots, existing concrete slabs, and remote hillside properties accessible only by chainsaw. Here’s what we’ve learned.
Why Every Container Must Be Elevated
The single most important rule for any permanent container installation: get it off the ground. Long-term ground contact causes corrosion from below — and once rust takes hold in the base of a container, it’s expensive and difficult to repair.
Elevation does more than prevent rust. It creates crawl space underneath the home for connecting septic pipes and water lines, and for future maintenance access. We install our container homes a minimum of 3 feet off the ground. For homes in rainy or flood-prone areas, we often go higher.
Before you dig a single footing, map out your full property layout: Where will the septic tank sit? Where does electricity enter the home? Where is your water entry point? These decisions affect where every footing goes. Change them after the foundation is poured and you’ll be chasing problems through the entire build.
The 4 Foundation Types We Use in Costa Rica
1. Cement Canisters — Our Preferred Method
For most of our builds, we use cast-in-place cement canisters. We drive rebar into the ground, then pour concrete around it in a cylindrical form. The result is a solid post footing that we can weld the container’s corner posts directly onto.
- 12-inch diameter for 20ft containers
- 18–21 inch diameter for 40ft containers
- Typically 4 feet high to create adequate crawl space
- 5–7 rebar sticks per footing, hammered into the ground before pouring
- Steel plates (salvaged from container cutouts) welded over the top of each footing to protect the cement and provide a clean welding surface
For two 20ft containers merged side by side, we typically use six canisters total — with two larger ones at the center merge point where the load is concentrated. A two-man crew can complete this foundation in a single day.
2. Wood Beams
A simple and effective option, particularly on soft ground where spreading load across a wider surface matters. Wood beams elevate the container cleanly and are the right choice when a client plans to relocate the unit in the future. For permanent installations in Costa Rica’s wet climate, we prefer concrete — wood degrades over time in contact with the soil.
3. Steel Jack Stands
An excellent option if your property has an existing concrete or asphalt surface. All of our Costa Rica projects are on dirt lots, so we don’t use jack stands here — but for urban builds on hard surfaces, they’re fast and effective.
4. Used Tires
We’ve used this option for clients who are clear that the container will be moved again within a year or two. Tires are free or nearly free, they elevate the container adequately, and the whole setup can be dismantled in an hour. For a permanent home, use concrete.
Foundation on an Existing Slab
If your property already has a concrete slab, you can place containers directly on it with very little additional work. The key requirements: the slab must be level (or shimmed to level), it must have sufficient load-bearing capacity for the container weight, and the corner posts must be welded or bolted to prevent any lateral movement. A container sitting level on a solid slab and properly anchored is a perfectly sound foundation.
The Structural Rule Nobody Talks About
Once your foundation is in place and your container is set, you may begin making cutouts for windows, doors, and merged walls. Here’s the rule that many first-time builders miss: every cutout weakens the structure. The weight of steel you remove must be compensated for by the weight of support steel you add.
Our general rule of thumb: The weight of the steel cutout must be matched by the weight of the support beams or posts you weld in to replace it. For large cutouts, add an additional foundation footing directly beneath each new support beam so the load transfers properly to the ground.
Keeping a Closed Container Moisture-Free
If your container will sit closed for a period before construction begins — which is common on remote lots — take these steps to prevent moisture buildup inside:
- Elevate the container immediately — even off used tires is better than ground contact
- Install a small internal exhaust fan on a timer to circulate air and pull out moisture
- Place moisture-absorbing crystals inside — available at most hardware stores, they last up to 45 days and cost around $5
We Build Container Home Foundations in Costa Rica
At ContainerHomes.net, we’ve built container homes on lots ranging from flat beachfront properties to steep jungle hillsides. Every property is different, and every foundation is designed for the specific conditions of that property — soil type, slope, water table, intended use, and whether the home will ever need to be moved again.
If you’re planning a container home build in Costa Rica and want to talk through your foundation options, get in touch. We offer consultations and we build complete homes from foundation to finish.
Want the complete foundation chapter?
Our 5th Edition book covers foundation types, footing dimensions, rebar specs, structural rules for cutouts, and 10+ real project photos from Costa Rica builds.
Jimmy Lee
Builder & founder of ContainerHomes.net. Based in Costa Rica. Designing and building shipping container homes since 2010. Author of Notes on Shipping Container Home Construction, 5th Edition.