I always thought that doors were supposed to be installed on top of the subfloor, but it recently pulled out an old door for replacement and I found that I was sitting atop the finished floor. Are new doors supposed to sit on top of the subfloor or the finished floor?

 

Do you mean an interior or exterior door? Normally interior is above the finished floor. Or installed on sub-floor, then jambs are undercut based on flooring installed. Exterior is on the sub-floor raised as necessary to allow clearance if required. At least that's the way I've always seen them.

 

Sorry I wasn't clear. Yes, I was referring to exterior doors.

It was an exterior door that I pulled out for replacement. I found that the door was sitting right on top of the finished floor. Aren't exterior doors supposed to be sitting on the subfloor, not the finished floor?

 

Yep...unless like I said they need to add material for it to clear the floor when opened. Like a PT 1x6 or deck board.

I'd guess that someone did a rehab and did the flooring while the house was wide open?

What kind of flooring was it? And did it extend all the way to the outer edge or just part way under the door?

 

I'm not sure, but I think someone might have done a rehab to this house years ago. I'm just trying to make it right now.

Now that I've looked at it again, it does look like someone may have added material for the door to clear the floor when opened. The house is on pier and beams. The soil has shifted in the past requiring leveling of the house. Also, when I look at the area the door was sitting on top... It is flush with the finished floor, but it looks like a deck board, or a 2x8 board. Very unusual. I don't know why someone would do that.

Oh yeah, the subfloor is 3/4" plywood running diagonally. The finished floor is just narrow strips of 3/4" oak. The finished oak flooring runs right up to the 2x8 board that the door was sitting on top of. That 2x8 board is flush with the finished floor.

Should I even bother taking out the 2x8 board and doing it right? Maybe, the old homeowner before me actually did it the correct way to shore things up.

 

Well...I don't think it's that odd. We've had questions here about problems with door swing clearance when people changed the finish floor from linoleum to hardwood or thick tile (for instance) in an entry way or kitchen. The common answer is to uninstall the door, add a spacer (like a 1 x 6), then re-install...bringing the interior sill level with the finished floor.

 

Ahh! I see what you mean. Ok, so when people have had open/shut clearance problems - a solution to this is to raise the area under the floor that the door sits on (ex: with a 1x6 wood piece) so that the metal exterior sill that comes with the prehung door is now flush with the finished floor. This is what you are saying, correct?

In my situation, the area that the door sits on, is already flush with the finished floor. And putting a prehung door on this area means the metal exterior sill that comes with the prehung door now sits a touch higher than the finished floor. Is this ok? Or should I remove the 2x8 wood piece that the door sits on top of, and replace it with a 1x8 piece? That would, in effect, lower the wood piece that the door sits on top of so that the finished floor would be flush with the exterior door's metal sill plater.

 

Yes, as long as the rough opening allows you to true up the door for proper operation.


If you mean the bottom of the metal sill...it depends on what you want to do. I've used 1/4 round or shoe moldings to make it look good if there is just a small gap (sealing well under the door, of course). If its a very small gap, color matched caulk might work as well.

If the difference in height is kinda extreme, constituting a trip hazard, then yes, going to a 1x8 might be a better option, as long as there is still clearance. Consider also that some people like rugs in front of the door.

 

I usually shum the subfloor with 1/2" plywood to raise the dior high enough to clear a thick rug.