My solution is to use two basic panels as the building blocks to assemble a building. The wall panel is a 2″ thick ‘c’ shaped panel 8′ long. 1″ holes are pre-punched in the flange near the top and bottom of the panel to run electrical wiring if desired.
The inside of the wall panel has a 3/8″ air space (thermal break), 1-1/2″ EPS foam insulation, and a pre-finished 1/8″ interior wall panel. There are also half panels (4′ long) and quarter panels (2′ long) that are used to create openings for windows.
The panels are joined together using ‘c’ clips that slide over the flanges of adjacent panels.
One 4′ x 8′ sheet of galvanized steel makes exactly two wall panels and two ‘c’ clips with zero waste. One 4′ x 8′ sheet of EPS foam makes exactly three foam inserts for wall panels, and three interior panels are cut from each 4′ x 8′ panel with zero waste.
The second type of panel is the roof panel. It is the same shape as the wall panel, but it is 3-1/4″ thick and 10′ long. There are no variations of the roof panels. The roof panels have the ‘c’ clip on the outside and the flat galvanized side is the inside. This makes the joint water-tight. A 4′ x 10′ sheet of galvanized steel makes exactly two roof panels with zero waste. The roof panels are insulated with 2″ thick EPS foam and the foam is covered with a 26 gage galvanized panel.
All of the wall panels for a 120 square foot building will fit in a compact truck level with the top of the bed before the foam and interior panel are added. When fully assembled they fill the back of a full-sized pickup to the top of the bed. Everything for 120 square foot building will fit in a full-sized pickup to about the level of the top of the cab. The components for sixteen 120 square foot buildings will fit in a 40′ container.
There are a few auxiliary components needed to assemble a building. The bottom sill comes in 10′ lengths and attaches the wall panels to the deck or foundation upon which the building is constructed. It also drains any water that gets between the wall panels to the outside of the building.
2″ ‘z’ flashing is used under the roof beams and around window openings. A 2″ x 2″ roof beam in 10′ sections is used atop one long wall, and a 2″ x 6″ roof beam in 10′ sections is used on the other long wall. Small ‘L’ brackets along each roof beam hold the roof panels on.
Everything was designed to assemble only with clips, but it became too complicated. The floor to wall attachments and roof to wall attachments now use sheet metal screws. This means you really need an electric drill to assemble the building, so I missed on that goal. I was also off on the cost. I estimate my cost in materials and labor to be close to $5,000. However, I bought everything at retail prices and only manufactured components for one building. I think the $2,000 price could be achievable with wholesale materials and a better manufacturing process.
It took me about 15 hours to assemble the prototype building, but I believe an 8 hour build time is possible once the kinks are worked out.
Overall I’m pretty happy with the way the project turned out. The building was easy to put together and everything fit quite well. The building is very solid.
When the panels are clipped together the joint is like an I-beam. The top and bottom sill and roof beam stiffen the walls in the horizontal direction. The resulting structure is rock solid.
I can’t tell yet how effective the insulation is. The walls have about an R-9 and the roof R-12.