I'm considering making a well insulated interior door and need to understand the door thickness implications for the getting a door knob. The door could be upto 3" thick - less if getting a door knob becomes a problem. I'd like to use a cheap off the shelf knob - possibly adding extensions.

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    Did you do any research before asking a question here? I did a web search for "door knob for thicker doors" and came up with many options, including extension kits and knobs for thicker than normal doors. Hinges and functionality of a door that thick is another problem to be addressed.
    – Alaska Man
    Commented May 21, 2018 at 18:01
  • I did, hence my suggestion of extension, but didn't really understand the options. Is this all I need to adapt one? handlesets.com/thick-door-kits/c8599
    – pathfinder
    Commented May 21, 2018 at 18:41
  • visit a hardware store that sells door handle sets .... see what they offer
    – jsotola
    Commented May 21, 2018 at 20:45
  • @jsotola - thank you for the tip, but why waste an hr or 2 and gasoline when then is a community of creative people with great ideas.
    – pathfinder
    Commented Nov 26, 2018 at 16:59

1 Answer 1


A standard lockset could be inset into the face of the door, so that 95% has full insulation. You will also need to consider hinge screw locations in the edge of the door.

  • You're suggesting recessed door handles?
    – pathfinder
    Commented May 22, 2018 at 17:42
  • I.e. putting some of your insulation proud of the door handle surface, except where it interferes with the handle. It's not even an inconvenience if you are using lever handles. Commented May 23, 2018 at 4:39
  • Was definitely over thinking the problem. I've now have a hollow core door and have attached rigid insulation except near the door handle. At some point, I might cover the insulation w/lauan - but this was simple and cheap enough.
    – pathfinder
    Commented Nov 26, 2018 at 17:04

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