The problem is that there was a previous plant there (processing material from the local tin ores) which left quite a bit of radioactive residue around the place.
The homes are built mainly from cinderblocks and corrugated tin, though several shacks appear to have been simply lashed together with whatever material could be salvaged.
After some experimenting, Norton settled on growing tin in the form of needles (about 50 nanometers in length) and adding textures to the material to create more surface area.