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# Ridge joist off square... help

#1
01-22-18, 12:18 PM
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Ridge joist off square... help

I'm putting a work shop with living space next to my home. All my block are up, ran my sill plate flush with the block wall, put my ridge joist on and when I checked it for square it's way off. When we put the block wall up and checked the wall it was in perfect square, give or take a 1/4 inch. I measured diagonally across my ridge joist, one measured 45' 1" and the other one 45' 6", 5 inches off. My ridge joist runs flush all around my sill plate, how can I be 5 inches out of square when the wall is square, what am I doing wrong?

#2
01-22-18, 12:58 PM
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Post some photos so we can see what you see.

I hope what you are calling a ridge joist is a rim joist.

Did you have the same tension on the measuring tape when measuring each diagonal?

#3
01-22-18, 02:53 PM
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I'm sorry, I was talking about my rim joist, had my mind on this problem. Yes the same tension on both measurements. Both block walls read 30x35 just what they're suppose to be. If you need more photos let me know, I can take more tomorrow during the day, thanks...

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#4
01-22-18, 02:57 PM
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I also did a 3-4-5 square measurement on each corner and they were right on..

#5
01-22-18, 03:00 PM
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First check that your rim lengths are equal on opposite sides. If they arent, that is one problem.

They would obviously be just as square as the foundation is, so... maybe the foundation isn't as square as you thought.

Did you measure outside corner to outside corner each time? Not outside to inside on one?

You can also check your corners for square one at a time... use 3:4:5. Or in your case... 24:32:40. Mark 24' from one corner one way... 32 from the corner the other way... the hypotenuese between those lines should be 40. If it's not that particular corner is not square.

#6
01-22-18, 03:01 PM
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It sounds like you are giving us the length and width of your block foundation wall (30 x 35) but when you talk about your rim joist are giving us diagonal dimensions. What are the diagonal dimensions of your foundation walls? It is possible for the block to have the correct length and width but still be out of square (parallelogram).

#7
01-22-18, 04:01 PM
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I always find it helpful to calculate what the diagonal should be. Corner to corner for a 30 x 35 rectangle should be 45' 1". Remeasure all sides and then both diagonals. Recalculate the diagonal if needed.

Bud

#8
01-22-18, 07:36 PM
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Bud9051, in my first post that is what I have for one of the diagonal measurement, 45"1", when I measure the other corner diagonally I get 45' 6". The actual size of the wall is 30x60, we put a center course of block across the center to make a living and garage area. When we took a diagonal measurement to see if the wall was square we went the total wall length, 60', it was dead on. We never did take a diagonal measurement for the 30x35 area. The only thing I can think of is maybe the center course of block is out of square and the outside walls run true. I'm going back out and remeasure everything again, length, width, and diagonally and I'll post my findings. Also I'm calling the guy who laid the block and have him come over and have him check it too. I'll keep you posted, thanks....

#9
01-22-18, 07:40 PM
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I'm also going to do the 3:4:5 square measurement but use the 24:32:40 method like XSleeper suggested.

#10
01-22-18, 07:46 PM
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If it is the dividing wall that is off, will you be able to fudge the plate one way or the other to square it up?

#11
01-23-18, 05:19 AM
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I agree with X, probably the dividing wall. I wrote this before I finished reading so will post anyway as may help.
****************
If the 4 sides are exactly correct but the rectangle is racked into a parallelogram then one diagonal will be less than the calculated while the other will be more.

So, there has to be a mistake in your measurements. If it is racked then the correct diagonal, when squared up, would be half way between your two diagonal measurements. Since that number is not what was calculated it mean your side measurements are not correct or your diagonal measurements are not correct.

Before this can be fixed you have to be sure your measurements are close to perfect.

Assuming your tape has a loop at the end that can fit over a nail, then install a nail in each corner ¾" in from each side. Also, put a support at the midpoint of the diagonals as that is hanging out in the air.

Bud

#12
01-23-18, 10:38 AM
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Ok new update... Took all my measurements this morning during the day, the last ones were at night, I was off. I lined up my rim joist flush again and this is what I got:

Dimensions on the wall, 30' width and 34' 6" length from outside to outside of block.
The rim joist are all the same length.
As per picture below I measured diagonally and got 45' 10" from point 1 to point 2. I got a measurement of 45' 5" from point 3 to point 4, I'm still out of square.
I also measured the garage part diagonally, it showed I was also 5" off. Does this mean the whole building is 5" out of square?

In my second picture I did the 12:16:20 square method, I came up with with 20' 1" from point 1 to point 2, 19' 10" from point 3 and 4, 20' from 5 and 6, and 19' 10" from 7 and 8. I hope you can understand all of this, I'm still baffled by all the inconsistent measurements. Any ideas on what to do next let me know. If this building is that far out of square the block contractor better come up with some ideas of his own. The amount of money I had to pay 4 union block layers for a days work you think they could have at least ran this building square....

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#13
01-23-18, 11:01 AM
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I have it sketched out on paper but can't tell from your labels on the pictures which legs are the 12' and 16'?

Can you tell me if they lay on the length or width? It matters when calculating the angles.

Bud

To be clear, each triangle has a 12' and a 16' leg. If we look at points 3 and 4 can you tell me if 3=12' or 16'? and then 4 would be the other length. Do that for all 4 triangles.

#14
01-23-18, 11:14 AM
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maybe the foundation isn't as square as you thought.
Yep, sounds like the whole thing is out of square.

#15
01-23-18, 12:26 PM
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ok, #2, 4, 5, and 7 are the 12' mark running the length of the building, # 1, 3, 6, and 8 are the 16' marks running the width of the building. Sorry you can't see it clear, I thought you could make the picture bigger by clicking on it, guess you can't. Anyways the block guy came over and took some measurements, when I seen him scratching his head I knew I had problems. We were trying to figure out what wall was off square but the weather here is in the 20s with high winds, we didn't stay outside to long. He took the measurements and said he'd try to figure out were the problem is and give me call. His first idea was that my footers lifted due to to cold snap we had but I told him to look at all the inside corners and block seams, not a crack in any of them, I don't believe that is what put this building off square. Have a carpenter friend of mine coming over and see how we can possible correct this problem, I'll keep you posted. Thanks for all your help, I'll let you know...

#16
01-23-18, 02:49 PM
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Another question, did you actually measure both 30' sides and both 34'6" sides?
And, I don't see any fractions, like 1/4", did you round off numbers?

From the numbers you have provided there still seems to be a measurement error.

Still playing with the numbers.

Bud

Sometimes it is easier to determine how things went wrong after you fix them. To that end, consider creating a huge rafter square 9', 12', 15'. Manageable in size so you can flip it around on all corners and physically see where things need to be moved. IMO

Last edited by Bud9051; 01-23-18 at 03:18 PM.
#17
01-24-18, 05:01 AM
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Bud9051, I did measure both sides and rounded up maybe an 1/8 or 1/4, was in a hurry and didn't think it would matter that much. The weather has been brutal here the past few days, blowing snow, high winds, single digits, and doing it myself I was in a bit of a hurry. At the end of the week we're getting a break, warm and sunny. I have someone coming over to help me so I'll measure everything again and give exact numbers with fractions this time.

I never made a huge rafter square before but it seems something I can do, I'll pick up a 10', 12', and 16' 2x4. Are these the exact measurements I should make the rafter square, 9', 12', 15' ? I do have a small rafter square here, if you could tell me what the angles are to cut and which 2x4 goes where I can make it. I believe the 15' goes on the diagonal side, 9' on top, and 12' on the side? I'm not a professional carpenter but I did work with my uncle building homes years ago as a laborer, cut, nail, and frame so I do have somewhat the basic knowledge. I want to thank you and everyone else for all the help and patience, hopefully we can figure out were the problem lays.

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#18
01-24-18, 06:08 AM
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You don't need to cut any angles. Toenail the ends of a and b together. Butt the ends together. C is your hypotenuse... lay it across the others where you have measured 9' and 12'' from the INSIDE CORNER where a and b meet. Lay c across those marks so that your 15' marks (measure 6" in from each end of a 16' long board) line up with the 9' and 12' marks on the inside edges of those boards. Screw it on top of the others.

You will be able to lay it on top of the wall. A and b will drop over the edge of the wall while c will rest across the top. Your ends can run wild because you are creating a triangle on the INSIDE perimeter of those boards. Its the same difference but takes no cuts to do it.

#19
01-24-18, 07:35 AM
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I sharpened my pencil last night and narrowed some of my assumptions and got the errors down into the 1" to 3" range. The more precise measurements will help further.

Here's an example that tells me the measurements aren't precise. Not picking on you, just want to show how the math points out the problems. The diagonal on corner #4 is 20' exactly so it is a right (90°) angle. If we now use the 30' width and the 34'6" length (360" by 414") and square the sides, add them together, and then take the sq root we get 129,600 + 171,396 = 300,996 The sq rt of that is 548.63 or 45.72' or 45' 8 5/8".

But the diagonal you measured between 1 to 2 was 45'10". That's 1 5/8" longer than expected.

I'll wait for more numbers before speculating.

X covered a "how to" on building the 3-4-5 triangle and if the sides are correct you get a perfect 90° angle.

As for who is to blame, it wasn't the fault of the footing layout, that has lots of extra width for the mason to play with. The mason who lays the blocks would typically set batter boards on all corners and run mason's string to define the 4 sides. That string will be dead on square and become his reference for setting the bottom row of blocks. His length, width, and diagonals would be very accurate and here they are not.

Bud

#20
01-24-18, 08:01 AM
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After you finish your triangle, It will also help if you put a short board diagonally across the corner where a and b are toenailled together. Maybe 2 ft long. That will help hold your corner on top of your rim.

#21
01-26-18, 10:46 AM
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Bud9051, it was a nice day so when back out and took more measurements, did it alone again, won't have any help until the weekend. My rim joist isn't nail to the sill plate yet so I'm hoping with two of us we can move it around a bit and hopefully get the end corners square. I hope these numbers will give you something better to work with and maybe closer to the problem. As per the pic I used the 9:12:15 method on the corners but I'm still worried about my diagonal measurements. I'm not sure if you can enlarge this picture but if you're having a hard time seeing it I can always try to make it bigger. Hoping with help this weekend maybe I can get these numbers closer for you. Thank you for all your time, hope this gets us closer to the problem....

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#22
01-26-18, 01:13 PM
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Enlarged just fine in Word. Top left triangle says 9', 12' with a diagonal of 14' 3/4". I think that was actually 14' 10 3/4".

Also, add the corner designations 1,2,3 and 4 as they were shown in the original photo.

Note, with two opposite corners at 15' 1" and the other two at 14' 11' approximately all will become very close by sliding one side to make the 15'1" come down to 15', small adjustment. But I need the corner designations to say which one.

I'll work on the large diagonals to see what is going on there.

Bud

Note the 9' and 12' triangle sides look reversed.

#23
01-26-18, 04:28 PM
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Ok I'll check that 14' 3/4 measurement again and let you know. That 9' and 12' triangle measurement I wasn't sure if it mattered which side, should I measure the 9' mark on the short side (width) and the 12' mark on the long side (length)? I'll draw up another sheet for you with the info you want. As far as the diagonal measurement I just thought of something, as I was running my level up the side of my block to the top of my rim joist I did notice a couple corners that leaned in at the top about a 1/16" or so, this would mean my rim joist is not sitting straight up and down on my sill plate, would that be throwing off any of my measurements? Going out tomorrow to make adjustments so my rim is perfectly straight top and bottom with my block. Thanks again for all the help....

#24
01-26-18, 05:37 PM
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I want you to know I enjoy calculating things, it is the old "use it or lose it" principle, and at my age hair isn't the only thing I'm losing. So, I'll stick with you as long as you can put up with me .

Along that line, the short and long full diagonals as shown are reversed. The two corners that are more than 15' will be connected my the shorter full diagonal. Picture a square or rectangle and you shift the sides to form a diamond. Two corners will move farther apart while the other two will move closer together.

Make a sketch based upon your initial photos so corners all correspond to those labels. Then just fill in the diagonals for the triangles and the full foundation.

Adjusting the calculations is a bit of a pain so I searched for a calculator and found one. I will be playing with it tonight. I'll post the link after I know how it works.

Bud

#25
01-26-18, 06:20 PM
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The long and short of it is that if your diagonals are 5" off, you need to make 2 1/2" of adjustment. The long corners need to come closer. So this will mean the top left corner needs to go left and up. The bottom right corner will go right and down. This will also shift the other corners obviously... until the diagonal measurements match. Seems like 2 1/2" divided by 4 would mean each side needs to move 5/8" off the foundation edges... to get it close.

Right now you have a parallelogram, not a square.

#26
01-26-18, 07:36 PM
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Here's the calculator I found and it seems to provide the same equations I was having to create. Still cumbersome but much easier to have the equations in hand.
https://www.calculatorsoup.com/calcu...allelogram.php

I and others here have done this many times so not sure why you are having so much trouble. Someone asked earlier if your tape was cloth or what. My 300' cloth taps has a bit of a stretch to it.

I agree with X that you just need the diagonals to match, however so far those numbers do not agree with the side dimensions or the right triangle numbers.

We will see how tomorrow goes.

Bud

#27
01-27-18, 07:01 AM
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Ok I'm going to take this one step at a time. Like I said I did this years ago but my Uncle did all the calculations, he just gave me the measurements and I did the cuts and nailed, I should have watched him do more of the important stuff and asked more questions, lol. I kinda get the jest of some of the stuff you're telling me but other things I don't really understand at this point, you may have to explain it to me as a beginner, lol. I have someone coming over this morning to help me square my rim, hopefully we'll get it squared and I'll send pics of where it's sitting on the wall and measurements. As far as the tape goes I just bought a new 100' and it not cloth more plastic like. I sent a beginning stretch which I'll add to as we try to square this rim. For right now to make sure everything is clear, you mentioned that my corner 9:12:15 marks should be reversed, are you saying that my 9' mark should be on my width walls and the 12' mark on the length walls? I'll start with that question first so I know we're both on the same page. Sorry to be such a pain, thanks..

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#28
01-27-18, 07:43 AM
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It doesn't matter which is 9 and which is 12.

#29
01-27-18, 09:44 AM
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My rim joist isn't nail to the sill plate yet
Before taking any measurements, you need to line up the rim joist to the sill plate at the corners and fasten with screws to prevent any movement of the boards while the measurements are being taken.

All measurements must be done on a flat surface(in the same plane). Any drooping or sagging of the tape will void the accuracy of the measurement.

Referring to the measurements on the diagram shown in post #21, I have calculated the diagonals using the measurements shown for the four sides:

45.68303 ft.
45.68987 ft.
45.69089 ft.
45.69772 ft.

Just my 2 cents. Good luck with your project.

Last edited by Wirepuller38; 01-27-18 at 10:34 AM. Reason: Additional text.
#30
01-27-18, 12:20 PM
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Well so much for that sunny day they were calling for, in the 40s but pouring rain, I just can't catch a break! I did manage to straighten my rim up and down so it's all flush to the block wall, also screwed my corners down. Don't think my carpenter is going to show up and stand around in the rain, but my friend did stay around until we pulled some measurements. They still haven't changed much and I'm still showing 5" off diagonally. Calling the block guy back again and see what he plans on doing about fixing this problem, I'm beginning to get a very bad feeling his wall is off. If worst comes to worst would there be any possibly way to square this mess up with my sub flooring, just asking, guess I'm hoping for a miracle uh?

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#31
01-27-18, 02:41 PM
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While you aren't busy, can you take the last image and label it with 1,2,3,4 as shown in the photo of the foundation. Also write garage on the side where that is. Sorry to be a DA but I want to be able to suggest moving a particular wall in a particular direction and I can't get the last two images to agree. That 14' 11" diagonal ended up in two different corners.

Thanks,
Bud

#32
01-28-18, 08:05 AM
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Hey Bud, working on everything you asked for. I also printed out the footer and wall diagram showing the whole length and width, I'll be sending all the measurement for the living space and the garage all on one sheet. The 1,2,3,4, you're talking about, is that the 4 corners I pulled the diagonals off of? After you get this next sheet you'll be able to see the whole living and garage area at once...

#33
01-28-18, 12:00 PM
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Thanks Grant,
Just to do some thinking out loud I'm agreeing with your initial concern, the 5" difference between the diagonals. The confusing part is that the small variations we are seeing in the corner diagonals doesn't seem to be enough to account for the 5" difference.

Now, there are some constants that help me judge the measurements you are taking. One is all rectangles or squares will have a total of 360° when you add up the angles in the 4 corners. Yours aren't doing that and it makes me wonder if the sides are straight. If any or all bow in or out then the right triangle testing doesn't work. I'll wait for the next diagram to suggest where to look but checking each of the 4 sides with a masons string might help. Stretched corner to corner (not diagonal) does the perimeter joist fall exactly in line with that string?

Note, the corner with the 14' 11" diagonal should have a similar diagonal in the opposite corner, at least something less than 15'.

Bud

#34
01-30-18, 09:22 AM
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Hey Bud, sent a few pics, hope this is what you wanted. Still measuring alone so I hope my measurements are on, by the time everyone gets out of work it to dark to see anything. My carpenter friend is out of town, just waiting for him to get back. In the pic of 1,2,3,4, this is how I pulled my diagonals, 1 to 2 and 3 to 4. Also I forgot to tell you about my center wall, the bottom 3 courses are 8" block and the 2 top courses are 6", not sure if that something important. Hope this helps, anything else you need just let me know, thanks....

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#35
01-30-18, 11:33 AM
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Just printed off the pictures and sketch and will sit down with some coffee and see what I can conclude, snowing out. I still see one diagonal that reads 14' 3/4" if that is correct it sure indicates a problem. Was it supposed to be 14' 10 3/4"? The opposite diagonal is 14' 11" and opposites should match like the 15'1" corners.

I'll be back.

Bud

#36
01-30-18, 12:45 PM
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OK, an update, the measurement corrections first.
As previously mentioned, the 14' ¾" measurement cannot exist and must be approximately 14' 10 ¾". That makes it very close to the diagonal on the other end of that whole house diagonal.

The other error/s are the two whole house diagonals labels are reversed. The diagonal from 1 to 2 must be the longer while the diagonal from 3 to 4 must be the shorter.

With my corrections here is the required adjustment. Side 1 to 4 needs to slide 3 ¼" towards 4. That adjustment will bring all 4 of the corner diagonals close to being 15' while bringing the large diagonals closer together.

Since this is a rather large adjustment you will need to decide how it will be implemented, foundation or framing on top or moving multiple walls. In theory, if you shifted all 4 walls by a little over ¾" the correction would be the same as moving just 1 to 4 by the 3 ¼".

Looking down at your drawing, garage to the right, those shifts would be.
1. Wall 1 to 3 down ¾"
2. Wall 2 to 4 up ¾"
3. Wall 1 to 4 to the right ¾"
4. Wall 2 to 3 to the left ¾"

Not sure how bad that will look.

The calculations I did are simple and I can post if you want. The big issue is confirming and correcting the errors I noted.

Bud

#37
01-30-18, 02:10 PM
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Sorry about that 14' 3/4 measurement again, this is the second time I did that. We're getting a lot of snow here too, I'll have to measure that one again, can't remember if it was 10 or 11. The block guy is coming tomorrow morning and taking more measurements, also he wants to take a diagonal measurement of the whole building. I'll keep you posted tomorrow on what we come up with. If it's not freezing again in the morning I'll push that rim box around to what you asked and let you know how that worked, thanks again..

#38
01-30-18, 02:27 PM
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The suggested 3/4" shift is a good step in the right direction. Then you need to make so small tweaks to make the diagonals equal, or reasonably so. Your target for diagonal should be 45' 7 7/8" So just under 45' 8" in both directions.

Good Luck.
Bud

#39
01-30-18, 02:30 PM
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Or the 5/8 shift in post 25.

#40
01-30-18, 06:00 PM
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You are right X, I just didn't have enough confidence in the measurements to make a guess back then. His diagram at that point has the short diagonal between the two less than 90° corners and one of those corners is way off. As it turns out the horizontal and vertical shifts need to be more than the 5/8" to add up to the 2.5" diagonal correction. But your approach was perfect.

Bud