I think in new construction the doors go on top of the sub-floor. I am doing a bit of a renovation and already have a finished wood floor. A new door is going into a space that didn't previously have a door, but now there is a nicely built clean rough opening to put a door.

Should I...

1. Cut the small area of wood floor out to place the door jambs on top of the sub-floor
   - OR -
2. Cut a small amount of the lower door jamb so that the door is the same level as the other doors in the house?
   

 

Normally when doors are set in new construction they are raised enough to allow the finished floor to slide under them. IF the new door will set to too high to match the rest - cut the bottom of the jamb [door if needed] so it aligns with the rest.

 

What is your finished floor? Is it exterior or interior?

 

Option 2. In new construction, all doors are set at the same height. So if you have a wood floor you check the opening for level, cut both legs but cut one leg longer if needed so that the head is level. The final result should be a door that's the same height as the other interior doors.

 

Whoops! Maybe I was mistaken then.

I just had some exterior doors all installed directly on the subfloor, and I didn't bother to raise the bottom of the door jambs to be at the level of the finished floor. I guess I messed up. I actually thought that doors are supposed to be installed directly on the subfloor and the bottom of the door jambs at the level of the subfloor.

In any case, where I am at now is installing the interior doors. I figure that I need to install them at the level of the subfloor to match all the exterior doors. So my options are either cutting some of the subfloor out so I can rest the door jambs on the subfloor. Or... just cut the bottom of the door jambs the width of the subfloor, and just have the door jambs sit on top of the finished floor. Both options are easy to do. What do the contractors do in this instance?

 

At the risk of repeating... option 2.

 

To the pros: I was thinking pre-hung exterior doors rest on the sub-floor. Am i wrong?

 

Exterior doors are often set right on the subfloor. They are slightly taller than interior doors due to the thresholds. When you will have a 3/4" hardwood floor inside, (or even durock and tile) you usually want to shim the door up from the subfloor with 1/2" plywood, otherwise the door will drag if a thick rug is placed on top of the finished floor in front of the door.

Exterior door jambs are usually around 82" tall. Interior doors are usually 81 1/2".

 

Oh no. This is bad. I had bought some exterior doors from Home Depot, and instead of installing them myself I had the Home Depot pros install them. They installed directly on top of the subfloor! And they didn't bother to even shim the door up 1/2" at all!

I don't know. I initially had questions about installing interior doors when I first posted the thread, but now I find out that my exterior doors where installed directly on the subfloor. Maybe I should just take all the exterior doors out and re-install them with a 1/2" shim directly between the subfloor and bottom door jambs.

 

You are probably fretting about nothing. If the door swings open with a rug in front of it thats all that matters.

The other jambs can be undercut with a jamb saw so the floor slips underneath. And if the doors are too close to the floor after floor covering is installed they can be cut.

 

Ok thanks guys. There is currently hardwood flooring in the house. Unfortunately, when I had the exterior doors installed I didn't know to have those exterior doors raised 1/2" above the subfloor. Yes, I actually had the exterior doors installed directly on top of the subfloor. Do you think I should go ahead and redo those exterior doors to raise them off the subfloor by 1/2"?

 

Will the exterior doors clear the finished floor ok when you open them? As long as the door will open I'd be inclined to leave it as is. You can always under cut the casing to slip the flooring under it.

 

Thanks marksr. Yes, the way the exterior doors are, they open into the house where I have finished wood floors. They open and shut fine right now without any entry rug.