Why should I check a window for Square?

[DerbyDad03]

The installation instructions for my replacement windows say to check both jambs for plumb, the sill for level, and diagonally for square.

What's the point of checking for square?

If both jambs are plumb and the sill is level, the only way the unit won't be square is if the manufacturer screwed up and made one jamb shorter than the other.

I check for that by making sure both the sill *and* head are level. It seems to me that checking for a centered bubble is easier than trying to ensure that the tape measure is positioned in the exact same spot for both diagonals.

Am I missing something?

[Wayne Whitney]

Checking the diagonals with a tape measure is more accurate than using a bubble level. Also bear in the mind that the jambs have some flexibility.

Cheers, Wayne

[Oren]

It gives me and idea of what I have to work with :-)

The fastener can pull a frame out of square; especially screws. Not to blame the install on the maker.

So the fasteners don't tweak the frame.

(these diagonals prove the square?)

-- Oren

"If things get any worse, I'll have to ask you to stop helping me."

[Tony Hwang]

Hmmm, Ever heard of double checking? To make really sure?

[DerbyDad03]

Oren said, and Wayne implied (I think):

"The fastener can pull a frame out of square; especially screws."

Step 6 of the installation instructions has the installer checking for plumb, level and square. Step 7 has the installer visually inspecting the weather stripping, reveal, etc. Step 8 says: "Once the window is plumb, level and square, install installation screws into the prefabricated installation holes in the jambs."

So, if the checking for square comes before the fasteners are installed, I believe my question is still unanswered. :-)

As far as a tape measure being more accurate than a bubble level, my experience has shown that it's pretty tough to accurately measure a ~64" diagonal by myself, but I can read a good quality bubble level in

4 different locations with no problem at all.

[mm]

So you've given one answer to your own question. Maybe it did that.

I don't think so. The glass is an inch long or a little more. A tinyt tilt can cause the bubble to move so little you won't see it.

The diagonal of the window can be 36 or more. And your tape has increments of 1/16 or 1/32 of an inch. 1/16th of inch into 45 inches is 720. I'm not sure what to divide by 720, but if something were

1/720th off level, do you think you would see it in a bubble's position?

How about, check both ways for the rest of your life and then report back to us which finds out of square more often. I'll do the same.

[Oren]

As the install goes... Use the longest level you have or have a steel for 8 foot doors or windows.

This is a good time to clean and remove nails, etc, that may be in the way - before the install. Nothing worse than having a nail interfere with this "squared frame" as you set the window.

Too reduce the pulling of the frame; pre-drill a hole suitable (slightly larger) for the faster. Then just button up the fastener. Loosen it to square up if you tweak the frame

Your RO might be square. Forget it now and square the window. Don't over fasten the window. Poor installs equal early failure.

A two foot or six foot level on an eight foot door will not work :)

-- Oren

"If things get any worse, I'll have to ask you to stop helping me."

[DerbyDad03]

The glass may be an inch long, but not the area between the 2 lines. A good level will have very little space between the lines and the bubble. Take a look at the bubble level on a Straight Line laser level. Unless they've improved them in recent years, the bubble level on them sucks because the bubble is too small compared to the lines.

Compare the welds in the 4 corners of a vinyl window. They are not a perfect match - at least mine aren't. Some have more vinyl buildup then others. Once the window is in the RO you can't get to the outside corners, so you have pick a spot on an inside corner. The irregularities in the vinyl could easily account for a 1/32" or more difference in the diagonals.

Monthly reports OK? We don't want to waste bandwidth. ;-)

[Joseph Meehan]

Yes, If they are not square (that means they have four 90º corners) then they can still have the same length tops and sides, but be a parallelogram. Think of the top moved to the left or right and then the two sides will not be upright. Not a good thing for windows.

Example: _ /_/

[Norminn]

Don't know whether it fits the question, but a window can be warped and still plumb and level. Lived in a rental once when the owner replaced windows in several small houses he owned. Old alum., new wood. The wood windows sat in the yard for about a month before the unhandyman did the work. They were warped and twisted and one side of a couple of windows protruded into the room whilst the other side was flush with the wall. Must have gotten them at a fire sale, because none were remotely the same size as original.

[DerbyDad03]

-- Think of the top moved to the left or right and then the two sides will not be upright.

Then they wouldn't read plumb on the level.

[Mike Dobony]

Remember the 3-4-5 rule. 3" over, 4" up will end up being 5" diagonal if square. Multiply these numbers until you have the maximum you can measure diagonally. Sounds like you have a pretty good sized window. You can also use a framing square to check the corners.

Mike D.

[Joseph Meehan]

-- Think of the top moved to the left or right and then the two sides will not be upright.

Then they wouldn't read plumb on the level.

While that is true, it is also true that measuring is a far more accurate way of measuring square than a level.

[Harry K]

No need to go the math route: measure cornter to corner and as long as they are identical, the window is square.

Harry K

[Harry K]

Speaking of warping. I built an addition, bought a new fairly expensive steel clad entry door. Fitted it, everything measured and plumbed level but the weather stripping would not close at the bottom corner. Called the supplier - they came down, checked and found the same thing. Gave me a new door and I got to keep the old one.

Harry K

[dpb]

Harry K wrote: ...

So what was actually wrong? If it wasn't fixable in place where it was, what was the value in keeping it? (Inquiring minds, etc., ... :) )

--

[dpb]

Easier, maybe, not necessarily as accurate.

The "trick" in my opinion, to making the measurement is to forget the tape and use a story stick w/ a pointy end (the proverbial pointy stick has a use here)...when the mark from one diagonal matches the other, you know the overall frame is square. Now you can then worry about whether there is any bow/twist/etc. in the the various components...

--

[willshak]

on 9/9/2007 10:07 AM Mike Dobony said the following:

Ah, yes! The Pythagorean theorem (paraphrased as it remember it). "In a right triangle, the square of the hypotenuse is equal to the sum of the squares of the two sides"

1st side = 3. 3 x 3 = 9 2nd side = 4. 4 x 4 = 16 Sum - 9 + 16 = 25 The square root of 25 = 5 (5 x 5) Therefore the Hypotenuse = 5 For longer measurements (i.e. decking), 6-8-10 works as well.

[Pete C.]

They are indicating to check plumb in the other plane, i.e. the plane of the wall, not the plane of the window opening. The window may well be plumb in that plane, and level at the head and sill, while being out of square if it was not shimmed properly.

[Mike Dobony]

True, but the OP said he couldn't reach the 64" diagnal himself and appearantly can't get any help.