20 Twenty SMI builds Custom Accessory Dwelling Units (ADU’s), Accessory Structures, Tiny Homes & Park Models in Salem. These homes are manufactured with both GreenFLEX and traditional stick-frame. Our GreenFLEX models are a world first, combining the durability of concrete, the super-insulation of modern EPS foam, and the mobility of a Park Model. Our ADU’s, Accessory Structures, Tiny Homes and Park Models come either as a shell or completely finished. The RV’s are tested to meet ANSI A119.5 & FPBR 1192 and we are certified by RVIA. This meets the standard for a RV Park Model in almost all states. Please refer to the applicability in your state and reference to the associated laws. Please note that in many states Park Model RV’s are for temporary/seasonal living and kept in RV Parks. This makes them attractive as vacation homes or rental units.