Converting a Used Container? Check These 6 Things First

A used container can be a great base for an office, studio, workshop or cabin, and it can save money over new. But a container that's fine for storage isn't always right for a conversion, and some problems are much harder to fix once insulation and walls go in.

Here are six things to check before you buy a used shipping container for a conversion. Once you've found the right box, see our buy a used shipping container options for custom builds and modifications.

1. The structure

A conversion usually means cutting openings for doors and windows, which removes some of the steel that holds the container up. Start with a container whose structure is sound:

• Corner posts straight and uncracked
• Top and bottom rails without serious bends or rust
• Cross members under the floor solid
• Roof without deep dents that hold water

A cargo-worthy or premium (IICL) used container is a better base than a wind and watertight one with lots of repairs.

2. The floor

Container floors are usually thick marine plywood or hardwood, often treated with pesticides to meet international quarantine rules. For storage that rarely matters, but if people will spend time inside:

• Seal the floor with an epoxy or similar coating, or
• Cover it with a new subfloor, or
• Replace it entirely

Also check for soft spots, rot and heavy stains, which are harder to deal with in a finished space.

3. What it carried

Most containers carried ordinary goods, but some carried chemicals or other cargo that leaves residue or smells. Ask the seller about:

• Strong smells inside
• Stains or residue on the floor and walls
• Hazard placards or labels

If in doubt, choose another container for a living or working space.

4. The paint

Container coatings are designed for marine use, and older containers may have coatings you'd rather not disturb or breathe in, especially when cutting or sanding. When converting:

• Wear protection when cutting, grinding or sanding
• Consider having the interior blasted and repainted
• Ask the seller about the container's age and paint

5. Size and height

• High cube containers give about a foot more headroom, which matters once you add insulation, a ceiling and a floor. In a standard container, the finished ceiling can feel low.
• Length: a 20ft suits a single room; a 40ft suits multi-room layouts.
• Straightness: dented walls make insulation and interior finishes harder to fit neatly.

6. Permits

A converted container is usually treated as a building. Check zoning and building rules before you buy, including:

• Whether the use is allowed on your property
• Building, electrical and plumbing permits
• Insulation, egress and fire safety requirements
• Foundation and anchoring requirements

Used vs. new for conversions

For many conversions, the time saved on prep makes a new container worth considering.

A conversion checklist

• Structure sound: posts, rails, cross members, roof
• Floor checked, with a plan to seal, cover or replace it
• No strong smells or residue from past cargo
• Paint condition checked, with a plan for the interior
• High cube, if headroom matters
• Permits checked

What to ask the seller about a container you'll convert

• What grade is it, and are there any structural repairs?
• How old is it, according to the CSC plate?
• Has it carried anything that could leave residue or smells?
• What's the floor condition, especially near the doors?
• Can I see photos of the interior walls, ceiling and floor?
• Do you offer interior blasting, painting or floor replacement as part of a conversion?

FAQ

Can I convert any used container?

Most, but a sound, straight container makes the job much easier. Avoid heavily damaged units and those with strong smells or residue.

Is the floor of a used container safe to live on?

Many floors are pesticide-treated. Seal, cover or replace the floor for spaces people occupy.

Should I buy new or used for a container office?

Used can save money; new saves prep time and looks better. It depends on your budget and finish.

Do I need a high cube for a conversion?

It's strongly recommended for offices and living spaces, for headroom after insulation.

Do converted containers need permits?

Usually, yes. They're typically treated as buildings.

Should I blast and repaint the inside of a used container?

For offices, studios and homes, many people do, to remove old coatings and give a clean surface for insulation. Wear protection, or have it done professionally.

Is a used container cheaper to convert than a new one?

The container costs less, but extra prep work, such as floor replacement, blasting and straightening, can narrow the gap. Compare total project costs.