Container Modification Planning

Start with the right box

A container conversion succeeds or fails on the unit you start with. Get the size, height and condition right and the rest of the build is carpentry and services. Get it wrong and you spend the budget fixing the base. This guide covers the decisions to make before you cut steel, and where AAD Logistics can save you a step with a ready-modified unit.

AAD sells containers and pre-modified units. We do not offer custom fabrication. If your plan matches one of the modified units below, buy it built. If not, buy the right base and engage a fabricator.

What AAD sells ready-modified

• Container garages: a 20ft or 20ft high cube with a full-width sectional door in one end. Delivered ready to park in.
• 12ft storage container: a personnel door and a window instead of cargo doors. A walk-in store room off the truck.
• 20ft Corten steel portable office: a container-based office with a marine plywood floor.
• Double door and open side containers: not modifications as such, but factory-built access options that often remove the need to cut openings. See the 20ft range.
• Ablution blocks and crib rooms: fully fitted amenities in 10ft and 20ft footprints.

Each of these avoids the two most expensive parts of a conversion, which are cutting and framing large openings and fitting out wet areas.

Choosing the base unit

Height

Buy a high cube. A standard container gives approximately 2,393 mm of internal height. After a floor covering, ceiling insulation and lining, that drops to a level that feels low. A high cube adds 305 mm and leaves a comfortable ceiling. AAD’s 20ft high cube and 40ft high cube are both sold new. See standard vs high cube.

Length

A 20ft (internal approx. 5,898 × 2,352 mm) makes a single room such as a studio, office or workshop. A 40ft (internal approx. 12,032 × 2,352 mm) makes two rooms or one long space. Two 20ft units side by side with a wall removed make a wider room, but that is structural work for an engineer.

New or used

New is the easier base. Panels are straight, the floor is clean and the coating is known, so cladding and lining go on flat. A used Wind and Watertight unit is a workable base for a workshop or storage conversion, but dents and patches show through lining and rust needs treating first. See new vs used.

Doors

If the plan needs wide access, buy it built in. An open side container gives forklift access along one full side. A double door container loads through from both ends. A container garage gives a vehicle door. Cutting these openings after the fact costs more than the price difference.

Understanding the structure

A container carries its load through the corner posts, the top and bottom side rails and the end frames. The corrugated wall panels stiffen the box but are not the primary structure. This is why openings can be cut in the walls, but every opening removes stiffness and needs a steel frame welded around it to put that stiffness back.

• Never cut a corner post or a rail without an engineer’s design.
• Frame every window and door opening with steel section welded to the panel and, where possible, to the rails.
• Keep large openings away from the corners, where the panels do the most work.
• If you remove most of a side wall, the roof needs support along that side.

A sensible build sequence

1. Design. Draw the layout, mark every opening, and plan where services enter. Check with your local council on approval for the intended use before you buy.
2. Footing. Prepare a level base. Piers at the corner castings suit most conversions. See preparing your site.
3. Delivery. A 20ft high cube arrives on a tilt tray. A 40ft on a side loader. Place it in its final position, because it is far harder to move once fitted out.
4. Cut and frame openings. Weld frames, then prime and paint the cut edges before they rust.
5. Treat and seal. Wire brush any rust, prime, and seal the floor if it is original timber.
6. Insulate. Steel sweats. Insulation with a vapour barrier stops condensation forming on the inside of the panels and dripping onto the lining.
7. Frame and line. Timber or steel battens, then plasterboard, ply or panel.
8. Services. A licensed electrician and, for wet areas, a licensed plumber.
9. Finish. Floor covering, joinery, paint, external cladding if wanted.

Insulation, services and approvals

Insulate the roof first, then the walls. Rigid foam bonds to the steel and acts as a vapour barrier; batts need a separate membrane. Add ventilation at both ends. Electrical and plumbing work must be done by licensed trades in your state. Council approval may be needed for a converted container, so check with your local council before you buy, not after.

Cost, delivery and next steps

Container prices are in AUD and include 10% GST. Delivery is AUD 745 per unit within the standard service area, shown at checkout. Orders are processed in 1 to 3 business days and delivered typically 4 to 7 business days after that. New units carry an 18-month warranty; cutting or modifying a container may affect warranty on the modified areas, so ask before you start.

If your plan is a garage, a store room, an office or a site amenity, look first at the ready-modified units above. Otherwise start with a new 20ft high cube or 40ft high cube and engage a fabricator with container experience.