MSG8 is machine stress graded to level 8 requirements.  This means that boards pass through a machine to test the strength and stiffness and is marked to the level it meets.  MSG8 is used in general framing and construction situations.

Number One Framing is a visual grade which has not passed through a strength and stiffness tester as MSG8 but is a high quality grade suitable for the same applications and was used prior to MSG8 being introduced.  Number One Framing we produce for outdoor premium use and is treated accordingly.