I am getting ready to install standard height interior prehung doors. I will have carpet installed afterwards and would like to set the doors at a good "standard" height to prevent having 1.) a big gap under the door and 2.) hopefully not have to take doors off and cut them down. Being a prehung door, it appears there is 3/4" of space already created due to the door jambs being longer than the slab.

I know I will have the best padding available for my carpet but I believe that is only 1/2" thick then a fairly soft (high shag) carpet which I would guess is 5/8 to 3/4" long carpet strands?...though I do not know for sure how that all can be used to calculate the door height for sure. SO I was hoping there is a good standard to use assuming carpet will be installed under the door slab.


Most places set the jambs on a scrap piece of 1/2" plywood, setting the bottom of the door at a minimum of 1 1/4" from the subfloor. If the subfloor is not level, make the lowest side a little higher, so the gap will be slightly bigger.

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  • Thanks, Jack. Is the idea to maintain at least 3/4" gap under the doors? I have found this is "required" if you do not have air returns for each room. However, I will have returns in the majority of my rooms, so I was shooting for a minimal gap. – Nic Dec 18 '17 at 17:07
  • The 1/2" shim under the jamb will just let the door go over the carpet without "sweeping" it. If it is a tall pile it may need to go up a little higher, perhaps another 1/8". But there will not be a 3/4" gap. – Jack Dec 18 '17 at 18:46

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