It has been raining cats and dogs for two days (fall wet season). I am looking at my newly installed but but not sealed patio door that is not screwed, not plumb-ed and not leveled and I am trying to understand why you need the entire door to be level plumb and square.

From what I understand the fixed door does not care much unless there is too much tension or pressure on it which could make it crack in time

The sliding door is more sensitive to level and plumb and square issues since:

-if will not close (if it is not parallel with the vertical side that it rests against, when closed)
-it will wear and tear the track if the track is not level

The door gets shims and it has around 1/4" space all around excepting the bottom side. The shims are used to fix it in position and to make it square and plumb but there is little tension that is transmitted from the structure to the door from the adjacent walls.

So my question is, why do you have to be so careful to make the entire frame square and plumb/level on all the edges ?

Edit: here is an example, exaggerated for the sake of argument enter image description here

  • Let me ask you all this question: is it possible to have an unsquare frame with the two doors installed and the moving door closed?
    – MiniMe
    Oct 31, 2019 at 20:51
  • Will the frame be load bearing?
    – Mast
    Nov 1, 2019 at 16:58
  • noway this is the plastic frames that keeps the doors in place and supports them. There should be appropriate framing for the opening where the door is installed that takes care of that load
    – MiniMe
    Nov 1, 2019 at 17:21
  • Could you please edit your question so that it is more readable? I'm having a hard time following your grammar.
    – MonkeyZeus
    Nov 1, 2019 at 18:13
  • did my best, do you feel better now?
    – MiniMe
    Nov 2, 2019 at 2:40

4 Answers 4


Out of square doors/door frames either do not close (if really bad) or seal properly; a 1/4" can create a significant gap in between the door and weather stripping allowing significant heat/AC loss.

Out of plumb doors either open or close from gravity which is simply annoying.

  • When you say door are you referring at the entire frame of just the door itself ? if the door (sliding or fixed) is not square itself that is a fabrication issue.
    – MiniMe
    Oct 31, 2019 at 16:45
  • 2
    My sliding flyscreen door had a hump in the lower track, making it a PITA to close. Luckily the glass sliding door didn't have as much problem. Nov 1, 2019 at 4:37
  • re: air gap: here is what the manufacturer recommends, I have exactly THAT door: farleywindows.com/wp-content/uploads/2017/12/… More interesting, despite of the advice received here ( in a different post) the manufacturer says I should add shims at the top of the frame
    – MiniMe
    Nov 1, 2019 at 11:51

Doors are made in rectangular shapes with nice right angle corners. When the door's frame sides are plumb and the top and bottom are level that defines a rectangular shape of the frame.

Having both door and frame rectangular ensures that the two will fit properly with even margins.

  • "even margins" means that the visible line between the door and jamb are the same thickness all around. (For the OP's benefit.)
    – FreeMan
    Oct 31, 2019 at 20:14

I'm thinking that you have answered most of your questions. under normal installations, plumb, level and square are needed. the most important one is square since that is the only way the sliding door will seal against the weather stripping and also be able to lock in the closed position. Think about it, the frame could be installed at an angle but as long as it was square it would function.

  • 3
    Yes and no. A moderate out-of-plane (twist) situation would cause alignment issues as well.
    – isherwood
    Oct 31, 2019 at 18:27

If you buy ready-made doors, each individual door will be flat and square to a close tolerance.

So if you want to fit two such doors neatly into one frame, you have to make sure free edges of the doors fit together neatly when they are closed, both closed doors are in the same plane, and that all the other edges fit neatly against the frame. You also need to ensure the doors don't swing open or shut under their own weight, the bottom of the doors doesn't contact the floor when they are open, the hinges are aligned properly so they operate freely, etc.

There are ways to achieve that when the frame is not plumb and square, but by far the easiest way is to make the frame plumb and square, and everything else will then "just fit properly".

  • I am talking about sliding patio doors, sorry for not being clear, it was implied in my post though
    – MiniMe
    Nov 1, 2019 at 4:21

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