Doors

Reply to: 25 year carpenter here...Here are the cold facts of the trade in almost every job in the world: If you are hanging a pre-hung door on a bare subfloor, you put the door right on the floor and install it. If you are hanging a door on a finished floor, you cut 3/4" off the bottom of the jamb, then install. Either way it gives you about 3/4" clearance over the finished floor. This is an "industry standard rule of thumb" for trim carpenters across the states. Knowing the exact height of the finished floor before installation and adjusting the door height is usually not practical, and can change. It is best to keep the door as low as possible, it can always be cut later if it needs more clearance for hvac considerations. It's really that simple. If the OP, or anyone else has 1.5 inches clearance, you or your contractor screwed up and hung those doors wrong. The doors were installed on a finished floor without cutting the 3/4" off the jamb. You could add a door sweep to the bottom of the door to take up some of the space...or...remove the trim/door, cut the 3/4" off the bottom jambs, and reinstall. If you have narrow door casing, keep in mind lowering the frame like this could expose unfinished sheet rock at the top of the door that might need to be patched/repaired. Good luck! Edit: Higher quality pre-hung doors are usually manufactured with 1.5" clearance under the door as described above, assuming the flooring will be premium as well, in the 3/4"+ range. Cheaper pre-hung doors give about 1"-1.25" clearance and this is because the rise of thinner floor systems for the mass consumer market. Again, either way 3/4" finish clearance is usually the result.

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Reply to: I agree with ryanr10. Yung needs to consider that it is not just looks - it is about sound and privacy as well. My master suite is right off the living room. I asked the builder to insulate the wall between the bedroom and the living room and then he put 3/4" gaps above the hardwood in all the doors. So what was teh point of the insulation? someone in the bedroom is kept awake by someone watching TV or talking in the living room. I also asked him to insulate bathroom walls. No one wants to hear the grunts and various other noises coming from the bathroom. (I have a bathroom backing onto the kitchen and surely do not want to hear that while I am cooking). And someone using the bathroom should have the right to feel they have some privacy. But my builder put 3/4" gaps under the doors. There is no privacy.

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Reply to: Joey, Manhattan and Yung are not correct. Your contractor did a bad job. Yung is correct about his clueless comment, he doesn't know what he is talking about (Manhattan's assumption is also incorrect.). HVAC systems do not rely on door gaps for balance, that's why every room has a return air duct. Bathrooms are the exception (no returns), which accounts for a small amount of total space/air of the entire system and the door is usually open. Even if it were closed, a very small gap would simply slightly limit the air pushed into the room from the HVAC. A 1/2" gap on a 32" door is 16 sq. in. or about the size of a 4 1/2" diameter hole. For drawing air into the bathroom, your exhaust fan is only 4" so there will be no imbalance. A 1.5" gap is like having an 8" diameter hole You have every right to blame the contractor for a sloppy job. The extension mentioned above is the best solution short of having it done again the correct way.

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Reply to: Ugh, I know Mattman is probably correct but I can't stand the gap in our place after replacing the upstairs carpet with LVP. Worse yet, we have only one register in the whole house. I am going to leave it and tell the next owner it's for HVAC efficiency.

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Reply to: Best answer right there from Mattman. Central air requires a pathway to move air. Otherwise you will have severe humidity issues, risk mildew growth, air balance issues. No one on this thread talks about why the 1” to 2” gap. All of you talk about how it should look. Operational function within your livable space investment is far more important than your “ideal” gap at the bottom you your doors. Those who state 1/4” to 3/4” are clueless.

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Reply to: http://www.ba-pirc.org/casestud/return_air/index.htm . http://www.finehomebuilding.com/2011/07/30/indoor-airflow-perfect-balance-vs-door-undercut

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Reply to: GN Builders, please cite the location of this ADA requirement. I have searched quite a bit and can not find anything within the ADA guidelines that specify the height of the door gap below the door. In fact, if you read the manufacturer's instructions for pre-hung doors then you will see that they do not reference ADA guidelines for trimming the jam of the door prior to installation to set the door height. In fact, after speaking to a door manufacturer, all door jams are built to the same size which is longer than required so that the bottom of the jams can be trimmed to set the height of the door from the ground to the user's desired height. They also stated that all of their machines are set to cut the same size and this increases speed and reliability of manufacture. Makes sense when you think about it from an engineering perspective. That said, I have seen most door gaps set to 1/2". In my opinion it is better to have to trim the bottom of a door slightly when installing it than to have to lengthen it. My remodel contractor installed my doors with the full door jam which left 1" plus of gap at the bottom of all the doors. This is unacceptable and I will be addressing this on the punchlist. All door slaps are set to 80" unless you build a custom door so you need to plan for changing door slabs in the future if you want a different look. There is a need for an air gap at the bottom for ventilation; however, the size of that gap is very unlikely to be greater than 1/2" for any door. If more gap is required it is easier to trim a door than to lengthen it.

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Reply to: That may be what happened. The contractor installed the unit with the maximum full jamb, without cutting, which I find a bit strange, just making the gap whatever the jamb decides. I like 1/4 inch from highest point. I don't like it more than 1/2 " when the door's closed, that's my preference. The contractor should have asked the customer what they wanted. To me , 1 1/4 inches is far too much, it looks bad. The bottom line is..... If the customer dosen't like the gap, it's wrong and needs to be fixed. Also, I prefer the same gap throughout the house. Alex

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Reply to: I'm seeing so much misinformation and speculation on this thread so I had to chime in. I trimmed houses for 10 years. Been on my own doing renovations for the last 5. So finish carpentry is my thing. I think what happened here is pretty simple. When you buy a new, off-the-shelf pre-hung door the jambs extend down past the bottom of the hung door by about 1 1/4" - 1 3/4" depending on the manufacturer. This margin is to allow for installation on top of subfloor so that when the flooring is installed you are left with a comfortable margin under the door slab. As a trim carpenter we always verified what thickness of flooring was to be installed so we could then adjust the height of the doors when we installed them. Sometimes this involves cutting off the bottom of the jambs to allow for less margin after the flooring is installed. When you install these prehung doors on top of a finished floor (as you did) you then have to cut down each one of these doors in order to give yourself a margin of 3/8" - 3/4" depending on preference. Some of those considerations/preferences may be things like: are you going to be using throw rugs on top of the finished floor? Are there special air transfer requirements? Or are there special noise/privacy requirements? Anything over 3/4" is certainly excessive unless there are special circumstances. Whomever installed these doors either didn't feel like cutting them down or cut them down poorly. 1" - 1 1/4" is not industry standard. 1/4" is certainly on the slim side though and I wouldn't recommend it. It doesn't allow for any sag, movement of the house (more of an issue with new construction), unlevel floors (more of an issue with old houses), and you will feel air resistance when opening or closing a door with that slim a margin. Not to say it won't work, it certainly will with the right circumstances, it just leaves no margin for error.

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