You can build walk-in freezer units in a range of different sizes, with different materials and to suit varied purposes. It is possible to create a small walk-in freezer in one section of a room, or develop an industrial-scale freezer that spans a much larger space, such as a warehouse. A large-scale freezer with plenty of room for walking around is required, for example, in a food-development company, but it costs significantly more to create.
Select the size of freezer you need for your individual requirements and purchase a walk-in freezer kit that can create such a freezer size. Make your own from scratch using insulation, sheet metal and foam. You will need to be skilled in cutting sheet metal to successfully complete the latter option.
Choose and purchase insulation material and a metal skin. Use extruded polystyrene (high moisture resistance) and polyurethane in large freezers as insulation materials, according to US Cooler. If you are looking to build a small-scale, in-room freezer, choose a skin that is easy to clean, robust and solid, such as G90 galvanised (expensive), aluminium (resistant to corrosion), galvalume (steel-coated aluminium), painted G90 (several colour choices) or stainless steel (very expensive, but strong).
Create the walls and roof of the freezer by cutting sets of sheet metal, inserting the insulation materials and injecting foam to clamp the two components together. A kit will already have the walls sandwiched together.
Purchase and install a refrigeration system that is both economical and energy-efficient. Select either a remote-control system, a pre-assembled remote system, a standard mountable system or a location-specific system (such as mount-top, saddle-mount, penthouse or roll-up).
Decide whether you need a floor to the unit, and install one if you do. Sweep the mounting surface clean, lay a sheet of waterproof sheathing down to create a moisture barrier and place the flooring on top. Secure the walls and floor with tongue and groove connectors, bolts or screws (and a screw driver), depending on the kit, or the type of joint you prefer to use.
Fit a door to the freezer. Take into account its position in the room and the side you wish to enter it from. Kits have ready-made doors that attach to existing hinges, but you can make your own using hardware store hinges. Make sure the door insulates, too. Caulk all the static joints.
Think carefully about how you are going to design and develop the freezer. Do not attempt anything you may find dangerous if you are not skilled in the art, such as using a metal cutting tool. For this reason, kits are recommended to the average DIY enthusiast or restaurateur. Ensure if you are using a paintable surface that the paint has been approved for the purpose by the correct body, such as the NSF. Use a special "Winter Kit" for outdoor installations, called an Exterior Cooler, according to Walk-In Pros. Do not attempt to introduce an indoor freezer unit to an outdoor space. Winter Kits have a unique crank case heater which keeps the compressor oil warm so it does not freeze up and prevent the unit from working properly. Make sure you avoid obstructing the door. Create adequate safety precautions and list them for others to see, such as keeping the door open when you are in a small-scale unit to prevent getting locked inside. The freezer and its components are heavy. Take care when lifting the door or roof and ask for extra assistance.