The printer generates a sort of open web joist structure that is probably strong and light; the layers are then bonded together into the structure. It's an interesting system in that there is room for wiring and insulation in those open webs.3Drs.org writes:
Using computer and 3D modeling software, the designs of the building can also take into account additions like insulation materials, plumbing, electrical lining and windows, which can then be easily outfitted once the rest of the structure is solid and standing.
In addition, it is very impressive that the printing material is recycled construction waste, industrial waste and tailings. WinSun plans to build 100 recycling factories in the country, one in every 300km, to collect and transform the waste into materials for 3D printing through special handling, processing and separation technology. "There will not be any waste from the construction of new buildings." said WinSun CEO Ma YiHe. WinSun expects 3D printing will save construction companies up to 50% on the cost.
A lot of bloggers and commenters are complaining that this isn't true 3D printing, because it doesn't look like Behrokh Khoshnevis' Contour crafting system and is printing out layers that need to then be lifted and put together. I don't see what their problem is; almost every 3D printing system is made of layers of 2D built up on top of the previous. Doing it this way where the layers are tilted up lets the designers create structural elements that can span openings a lot more easily. It is extremely clever, using common materials very efficiently.
So far the only source of information is 3Drs, and a line on WinSun's website that says "3D printing buildings is no longer a dream"; I have written the company and will report when more information is available.