I'm about 95% finished putting new doors and a top on my 20 year old brick smoker. When I originally built it I didn't know what I wanted to do for doors, so I just made some quick ones out of wood and used a chimney clean-out door for the firebox door. It worked, but everything leaked air like a sieve and was difficult to control sometimes.
Below are a couple pictures of the original setup.
I got to my 95% finished point about 3 AM New Years Eve. Started a fire, let it burn until noon and then put a turkey and three slabs of ribs in the new top chamber. It works!!! And I can't believe how well sealed all the doors are - close to zero smoke leaks out anywhere. Below are some pictures:
Picture below: Back of smoker - round thing is old exit for smoke stack.
Back wall is three plies of spruce that you see here - plus a 3/4" hunk of ply on inside.
Top of two plies of spruce (one bent on the outside), about 1.5" insulation, and then a steel liner on the inside.
Front door is 5 plies spruce.
New top and doors for cooking chamber. I doubled my cooking chamber volume.
Below is entire smoker.
Same as above only viewed from firebox side.
I can hardly wait to do some more smoking!!! Ribs and turkey New Years Eve were wonderful!