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Paul8434 01-31-2013 06:48 PM

Rough Opening for Interior French Door- Tolerances for Level
HI All,

I am installing a set of interior french doors.

I am enquiring on what is reasonable for level prior to installing the jambs and doors.

The height between the header and floor drop 9/16" from one side to the other.
In further investigation about 5/16" is the result of the floor sloping.
The balance 4/16" is the result of a crown in the header.

The opening was an exisiting opening without any doors, so i simply framed the rough opening by using the existing header and bring in the walls to the specified width.

My question lies with the slope in the floor.

How do i compensate for the slope in the floor with my Jambs.

Lastly the floor covering will be 3/4" hardwood.


woodworkbykirk 01-31-2013 07:16 PM

determine the height of the door header and make it dead level.. the jamb legs have to be cut differnt lengths to accomodate the out of level floor

Paul8434 01-31-2013 07:36 PM

Thanks for your very fast response.

Would there be any reason to shim the low side to level or stick with trimming the high side.


woodworkbykirk 01-31-2013 08:36 PM

it depends on the situation.. if you have a finished floor down you have to cut the jamb legs exact, if the floor isnt down yet you can just lift the low leg til you get the header level, reason being the jamb leg and casing gets undercut so the flooring slides underneath leaving no gap between the floor and jamb assembly

joecaption 02-01-2013 09:20 AM

If I understand you fully, trying to install any double door is hard enough when everything is square and level.
Trying to do it over a sloped floor would be a nightmare.
Shimming under the threshold would leave voids.
What I've done many times in older homes is make some tapered shims to form sort of a dam and filled with self levelling non gypsom floor leveler.
Now you have a perfectly flat surface to set the door on and the threshold makes 100% contact.
If you do not take the time to properly flash under that door before it goes in it will fail 100% of the time.

woodworkbykirk 02-01-2013 03:57 PM

joe.. your point is very valid, however this is for an interior door,, if you need flashing under this particular door chances are someone has a bad habit of leaving the kitchen sink running with the plug in.

joecaption 02-01-2013 04:00 PM

Oh poop, totaly missed that one good catch. My bad. Why not take the time to figure out why it's not level and fix that under the floor?

Paul8434 02-04-2013 12:33 PM

Hi Joe,

I had to think long and hard on wether to fix the slope in the floor.

I have a crawl space so there was an opportunity for me to jack of the joist or at least investigate further on the root issue.

In the end my relative lack of experience in the matter ruled.

I did shim the lowside per Kirk's comments. The door was installed over the weekend and i only missed the first half hour of the football game. The door sits plumb with proper margins between door and head jambs.

I will likely try and shim the floor when i install the finished flooring as my next step to ensure the margin between the floor and the door is somewhat uniform.

In reviewing my relatively well built home i note the floors slope across most interior doorways. Not sure why this occured other than poor framing. I havent noticed any settling in the drywall etc.

Although out of the scope of this thread i will try and investigate further how to rectify the sloping floors for my own general interest.


woodworkbykirk 02-04-2013 02:35 PM

paul. if you attempt to jack the floor up now that the door is installed youll throw off the door in the process

Paul8434 02-04-2013 03:19 PM

Hi Kirk,

Agreed with your comments on throwing the doors out of plumb if the floors are adjusted with jacks etc.

I will likely try and pad out the floor with tar paper to try and bring the floor to level with the door.

Jacking up the floor is beyond my expertise at this point, but i will follow up with a fact finding tour of my crawlspace and attic to see if i can narrow the source of the slope. But this is more for building my skill set for future remodels.


woodworkbykirk 02-04-2013 06:48 PM

jacking up the floor wont throw the door out of plumb it will throw the header out of level. as the door jamb is attached to the jack studs.. by jacking up the floor it will push the bottom plate and the framing up with it.. unless you plan on take the door frame out before you do this

when older homes get lifted in order to create a full basement door frames get thrown totally out of wack as the structure will shift

mknasa dad 02-06-2013 07:35 PM

Only thing WWBK forgot was that the doors will need to be cut down as well

jagans 02-06-2013 07:40 PM

20 points deducted from Joe for saying "My Bad" The next person that says that around me is getting the Louisville slugger.

The door has to be installed plumb square and level, irrespective of the opening. Got it?

mknasa dad 02-06-2013 08:49 PM


Originally Posted by jagans (Post 1111280)
20 points deducted from Joe for saying "My Bad" The next person that says that around me is getting the Louisville slugger.

The door has to be installed plumb square and level, irrespective of the opening. Got it?

Gonna be hard to get it square since the jambs would be cut, now wouldn't it???

jagans 02-07-2013 08:57 AM

The length of the jambs has nothing to do with whether the door is square (to itself). On prehung doors, (Is this prehung?) the jambs are made longer to allow for rug etc. You want it level and plumb so the doors don't swing by themselves.

A door can be hung square, level and on plane in spite of its surroundings with shims.

Is your structure sound? 9/16" is a lot in 5 or 6 feet.

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