Decking the final piece
Decking is the plywood that covers the joists to make up the floor.
Just like floor joists are thicker then the studs in walls the Decking plywood material is thicker then the sheathing plywood that covers the outside of the home. In new homes 3/4 inch plywood or OSB decking is used and it should be glued to the Joists. This is not a step that can be missed because without the construction adhesive you will end up with squeaks and pops.
Another feature of Decking for floors is its Tongue and Groove. This makes positioning the plywood a little more difficult as you work the tongue into the previous pieces groove but it is important because it locks the whole floor decking together in one piece.
In older homes you may find that they used boards instead of plywood this is not a problem because you can usually match up any area that needs to be fixed with new plywood decking and at worst you can shim the joists with strips of 2x material to get the proper level.
As we included rafters in the Horizontal Support system we also include the roof sheathing in the Decking because it supports both wind and snow loads it needs to be handled a little different then wall sheathing.
Roof decking does not have tongue and groove ends and it does not need to be glued but it is important that you use 1/2 inch plywood instead of standard OSB sheathing material because it will need to withstand much more rain, ice, wind loads and rot.
When you install the roof decking you should use clips between the 16″ or 24″ spans of the roof rafters to provide additional support.