To answer TXDVR. I am a newbe at smoking, but not at at construction techniques as I have over 50 years experience as Civil/ Structural Engineering Designer.
Structurally you need to support your smokehouse on a proper foundation if it is a permanent structure, similar to the one being discussed in this thread. A slab foundation is OK but will increase the height of the smoke house if the slab is at grade. A better approach is to build concrete footers and and masonry walls, filling the interior space of the foundation with a concrete floor. This design can lower the structure into the ground keeping the height more reasonable.
In my opinion, if you are creating in effect and "oven" it needs to be insulated or all the heat escapes. I good choice for insulation is a foil faced hard foam board 1" thick or more. The insulation also protects the wood construction from any concerns from excessive heat creating a fire risk. Once the smoke house is used a few times the smoke will cover all of the interior surfaces with a coating of creosote forming a protective barrier in itself, so I can not see any advantage to using expensive wood such as cedar other than for exterior appearance and weather durability. Sheet material, such as primed T1-11 will work just as well, but will need to be painted.
And of course, you need airflow control both in and out. From what I can determine, a chimney damper is not a must, but I opted to use a commercial smoker accessory supplier steel pipe chimney with a slide plate that can close the outlet. This does two things: 1. provides some degree of Temp control and 2. prevents, when completly closed,any chance of rain or creatures from entering the smoke house.
Not an answer to any question but just a note. I found the more difficult problem to solve was how to keep the smoke from seeping out around the smoke house door and the firebox door. Even expensive gasket materials doesn't seem to do the job. I have minimized leakage but have not been able to eliminate it.