Getting my Blockwork Square

[ddurrett896]

Building a 24x20 and laying out my block corners before my buddy gets here to help. The detached garage runs parallel with my house, so I'm using that wall as the reference for the new building.

Measured 9' off the house to start, then took measurements off of that wall...20' wide. I've got all my width and length measurements dialed in, but there is a 1" variance between the corner to corner measurement.

Went to took the width and length measurements again, they are right. Same with the wall parallel with the house. What am I missing? Thanks!

 

[BukitCase]

If you're using the same tape measure for all measurements, then the only possible thing is that your wall that's further from the house is NOT in the correct location. If it was, your diagonals would be identical. try running strings along ALL outer corners - the one along the house should be 20' exactly (it likely is) - then measure from the inside front corner along the string that's 24' long - make a mark on the string that's 16' from the inner corner, and mark the 20' long string 12' from that same front inner corner -

Now, WITHOUT disturbing the string (helper would be good) measure from the two string marks (you'll be describing a triangle) - between the two marks should be EXACTLY 20' -

I'm betting they're NOT. if you followed what I wrote, you just used the old "3-4-5" rule, which holds true with ANY multiple(s) - that ratio of sides will give an EXACT right angle at the corner.

odds are about 99 to 1 that, even tho your sides are all correct length, you actually have a parallelogram but NOT a perfect rectangle. This means that your outer 20' wall is either too far forward or backward.

With 20x24, your diagonals should be 374.89"...

HTH... Steve

 

[ycgoat]

I had a problem like this last summer, and it ended up being, I was using the end wrong. It was supposed to for looping around stakes but there was a tab that had to be folded out. I was excavating so at that point it was not critical. I would expect you have a parallelogram.

 

[manwithtools]

Look up Pythagorean theorem, also known in the construction trade as the 3,4,5 Rule. Your corners are not truly square. Measure one direction from the corner 9' and place a mark, measure the other wall 12' and mark, the diagonal measurement between the two marks should be 15' if the walls are square to one another. Adjust as required.

.

 

[readhead]

Is there a footing or slab that you are trying to line up with? If so, don’t assume that it is square.

 

[Uncle murph]

Building a 24x20 and laying out my block corners before my buddy gets here to help. The detached garage runs parallel with my house, so I'm using that wall as the reference for the new building.

Measured 9' off the house to start, then took measurements off of that wall...20' wide. I've got all my width and length measurements dialed in, but there is a 1" variance between the corner to corner measurement.

Went to took the width and length measurements again, they are right. Same with the wall parallel with the house. What am I missing? Thanks!

When you say corner to corner I assume you’re measuring diagonally,if so you need to shift the long wall back.You can usually get really close by just running a line around bloks set at the corner points and then follow the square of the block.Spend the time to get it right,it lays up a lot easier and makes framing easier as well.That said,you should recheck for square when attaching the plates.

 

[nadogail]

In the grand scheme of things a single inch difference will be within tolerances.

 

[brownbagg]

you need a steel tape

 

[CraigStu]

I don't know exactly how far along you are. Are your block corners fully mortared together? If they are I am with nadogail, don't worry about it. Just keep it in mind and when you fasten the stick built wall to the top of your block foundation let it overhang enough to get it square. If you are going all the way up w/ block you will still be laying a 2x6 or 2x8 on top of the block for trusses to fasten to, so fudge those a little.

 

[ddurrett896]

I don't know exactly how far along you are. Are your block corners fully mortared together? If they are I am with nadogail, don't worry about it. Just keep it in mind and when you fasten the stick built wall to the top of your block foundation let it overhang enough to get it square. If you are going all the way up w/ block you will still be laying a 2x6 or 2x8 on top of the block for trusses to fasten to, so fudge those a little.

Nothing mortared, just stacking block in the corners to get my measurements.

 

[Skiff Builder]

Building a 24x20 and laying out my block corners before my buddy gets here to help. The detached garage runs parallel with my house, so I'm using that wall as the reference for the new building.

Measured 9' off the house to start, then took measurements off of that wall...20' wide. I've got all my width and length measurements dialed in, but there is a 1" variance between the corner to corner measurement.

Went to took the width and length measurements again, they are right. Same with the wall parallel with the house. What am I missing? Thanks!

You have your 20' wall line drawn. Mark each end of that line. If alone, drive a conc nail or screw each end temporarily. Hook end of steel tape there.
Measure out 24' and at next corner swing an arc about 6 or 8"
Still hooked to same nail-Measure out 31'3" and swing an arc at the opposite diagonal corner.

Now hook tape on other end of your original 20' line.
Repeat the arcs for 24' and 31'3"

Where the arcs cross are your square corners. This will take 10 minutes, accurate, no back and forth.

 

[Zeke]

You have your 20' wall line drawn. Mark each end of that line. If alone, drive a conc nail or screw each end temporarily. Hook end of steel tape there.
Measure out 24' and at next corner swing an arc about 6 or 8"
Still hooked to same nail-Measure out 31'3" and swing an arc at the opposite diagonal corner.

Now hook tape on other end of your original 20' line.
Repeat the arcs for 24' and 31'3"

Where the arcs cross are your square corners. This will take 10 minutes, accurate, no back and forth.

Basically the 3,4,5 method. Any multiples of the 3,4,5 method will work. The larger the better.

I agree given the size of the slab that on inch diagonally isn't much to fret over and can easily be corrected during framing. I'd be more concerned about level or slope and 'birdbaths'.

 

[Skiff Builder]

Basically the 3,4,5 method. Any multiples of the 3,4,5 method will work. The larger the better.

I agree given the size of the slab that on inch diagonally isn't much to fret over and can easily be corrected during framing. I'd be more concerned about level or slope and 'birdbaths'.

It is , but unlike using multiples of 3/4/5, this plugs in the exact values of the foundation size. No intermediate measuring or too much back and forth. Swing the arcs- where they cross is are the exact corners of your project -in square.
A sq + B sq= C sq
20 sq +24 sq= 976
Sq root 976= 31.24



Another way, not using 3/4/5, is to measure out the same distance from a corner - say 14'. Just multiply whatever distance you choose by 1.41 to get the value of the diagonal.
Ex.14 x 1.41= 12.59.

Another way - with framing square
Use your tape measure from 20" on the tongue to 24" on the blade. 31.25"

Who knows how to draw a perpendicular line using dividers?

 

[joes169]

How deep into the ground are you? If you're working around a center unexcavated plug of soil, you must be using 2 levels to plumb above it? I'm a second generation mason, and it took me a lot of years, and maybe hundreds of foundations, to realize 2 things: I can't pay-out by myself and it's always better/ more accurate to take the time to set-up corner poles. If the corner poles are square, the foundation is always perfect. I use 2" x2" .125 wall steel tubing with base plates I made years ago, but there's no reason that you can't use lumber as well.

 

[Jackfre]

Did you set up batter boards on the outside corners. This is pretty straight forward with them. Establish that first string line referencing the house wall. Set that string/location on the batter board. Measure for the end wall and pull that string to the other corners BB. Use the 3/4/5 method to square that to the first line. Once set do the same back to the house. Check you diagonals.

 

[readhead]

No. It is 6'-4 13/16". There must be a lot of weird buildings where you live.

 

[Krfjkm]

If you're using the same tape measure for all measurements, then the only possible thing is that your wall that's further from the house is NOT in the correct location. If it was, your diagonals would be identical. try running strings along ALL outer corners - the one along the house should be 20' exactly (it likely is) - then measure from the inside front corner along the string that's 24' long - make a mark on the string that's 16' from the inner corner, and mark the 20' long string 12' from that same front inner corner -

Now, WITHOUT disturbing the string (helper would be good) measure from the two string marks (you'll be describing a triangle) - between the two marks should be EXACTLY 20' -

I'm betting they're NOT. if you followed what I wrote, you just used the old "3-4-5" rule, which holds true with ANY multiple(s) - that ratio of sides will give an EXACT right angle at the corner.

odds are about 99 to 1 that, even tho your sides are all correct length, you actually have a parallelogram but NOT a perfect rectangle. This means that your outer 20' wall is either too far forward or backward.

With 20x24, your diagonals should be 374.89"...

HTH... Steve

Great explanation— Thanks!

 

[Uncle murph]

I don't know what these people are talking about 3, 4, 5 or multiples thereof. Everyone around here knows that you mark down one of the sides 4', the other 5' and the distance between them will be exactly 6'. If it's not 6' you aren't square. Try that with your 3,4 ,5 triangle....

???

 

[firebirdparts]

Building a 24x20 and laying out my block corners before my buddy gets here to help. The detached garage runs parallel with my house, so I'm using that wall as the reference for the new building.

Measured 9' off the house to start, then took measurements off of that wall...20' wide. I've got all my width and length measurements dialed in, but there is a 1" variance between the corner to corner measurement.

Went to took the width and length measurements again, they are right. Same with the wall parallel with the house. What am I missing? Thanks!

A parallelogram can exist with two of the 4 sides parallel to the house. That does nothing to make it square. Just obey the corner measurement. It's not confusing at all.

 

[rayra]

BukIt covered it. Follow his directions. Until your diagonal measurements match.

 

[egdede]

???

Sometimes i drink too much.

 

[CraigStu]

A parallelogram can exist with two of the 4 sides parallel to the house. That does nothing to make it square. Just obey the corner measurement. It's not confusing at all.

I agree. I am sure this 3,4,5 thing has it's place but jeez. He measured his 2 diagonals and they were off an inch. Move two corners 1/2 inch each and his diagonals will be perfect. Seems very simple to me.

 

[andyvh1959]

How about what tape you use? When you do the 3-4-5-corners, or 6-8-10, a good retractable steel tape measure should do right? But to measure the 24 x 20 diagonals would a narrow 50' steel tape be better for the 31'-2.88" length? I'm thinking how much drop a heavier steel tape may influence the result unless it is really pulled tight. Or, if you get the same diagonal with the same pull on the tape, the droop of the tape is a lesser issue?

 

[CraigStu]

andy that is a good point. I would look at the droop and try my best to make it equal for both measurements. One could easily stand up a yardstick and then actually measure the droop.

 

[Dig Doug]

Building a 24x20 and laying out my block corners before my buddy gets here to help. The detached garage runs parallel with my house, so I'm using that wall as the reference for the new building.

Measured 9' off the house to start, then took measurements off of that wall...20' wide. I've got all my width and length measurements dialed in, but there is a 1" variance between the corner to corner measurement.

Went to took the width and length measurements again, they are right. Same with the wall parallel with the house. What am I missing? Thanks!

how Is this going? Did you figure it out?

we need some pics of your progress!

 

[ddurrett896]

how Is this going? Did you figure it out?

we need some pics of your progress!

It's dialed in. Ended up building 2 corners, pulling the diagonal measurements and marking the footer. Then pull the lengths and set at the intersection.

 

[NUTTSGT]

Glad to see you got it worked out.

Unless you do it a lot, a layout by yourself can be aggravating at times. The worse is when the mind gets stuck in that "rut" and you can't unthink what the hell is going on.

 

[MBfreak]

The "3,4,5 rule " is only valid on a flat surface area.
If the surface has a bow in it, your diagonals will be off.
Ola