SLI Prefab System Turns Construction Upside Down
Images credit Doug Scott
Jetson Green and MocoLoco are showing the new prefabricated building system from Sustainable Living Innovations, or SLI. It is a fascinating and innovative technology that really does turn building multifamily residential construction upside down.
Most construction works from the bottom up; SLI uses lift-slab construction, that works from the top down. The great benefit of lift-slab is that you don't need any formwork; you pour the slab on grade, and pour each of the slabs on top of it in a stack. It can faster, cheaper and usually safer, as workers are at ground level (with occasional exceptions)
Short video of construction sequence
After the slabs are poured, a structural steel frame is built around them and then the upside-down fun begins, as the top of the building is hoisted up first and bolted into the steel frame.
All of the parts for the next-to-top floor are then loaded onto the slab, including prefabricated service cores containing all of the electrical and mechanical components. They are then raised with the floor slab and connected. It is all very clever and slick.
I do have some issues and questions, and wrote to the architects two weeks ago to resolve some of them. Never having received an answer, I discuss them here:
UPDATE: Discussion with architects about these issues coming soon.
Is it Green? The architect is proud of the fact that the units are wide and shallow and have floor to ceiling glass; the single loaded corridor design creates a lot of surface area relative to floor area compared to conventional plans, and a lot more glass. It makes for a gorgeous unit, but it is not the most energy efficient way to do a floor plan.
They then cover it in the rendering with every green gizmo known to mankind, from green roofs to solar panels to wind turbines. It is the typical bolt-on green approach: take an inefficient glass covered building and throw green stuff at it.
Is that exposed steel allowed under the code? The codes may have changed since I last built in steel, but I would have thought that it needs some form of fireproofing. There are special intumescent paints that foam up and protect steel, but they are expensive and I do not believe they are approved for external use. There are other techniques, such as keeping the steel a certain distance away. I don't know the answer; I asked but they did not respond.
Is it really cheaper than wood? The architect notes that most low rise residential buildings are made of wood. They are also built really fast and cheap. He claims that the SLI system is faster and cheaper; That is going to be really tough, and really amazing if they pull it off, because it is a stronger, safer and better way to build. Even if it isn't cheaper, the quality, durability and speed are worth a premium.
If we are going to stop sprawl, we have to provide attractive and affordable alternatives. Conventional multifamily wood construction suffers from noise and quality problems; the SLI system is a promising alternative.
More at Sustainable Living Innovations.