# A transit won’t set post distance, right?

#### paperfist

##### Diamond Member
I need to set 4 posts equal distance from one another. So I rented a laser to do this. I didn’t check what was in the case and now I have a transit which I think will only set height?

Rental place is closed till monday

#### lxskllr

##### No Lifer
How distant? You can do it with a tape, and figuring triangles if they're close enough. To kinda answer your question you may or may not be able to do what you want with a laser or a transit. What are you trying to do?

#### paperfist

##### Diamond Member
How distant? You can do it with a tape, and figuring triangles if they're close enough. To kinda answer your question you may or may not be able to do what you want with a laser or a transit. What are you trying to do?

Damn lxskllr you know everything!

I'm trying to set 4 - 6x6 posts in a square 14' apart. I was using the 3 4 5 method, but it got aggravating with a tape. So I called up the local rental place for a laser that would do it and I think they gave me the wrong tool.

#### lxskllr

##### No Lifer
Your cross pull would be 19' 9-5/8". Unless the ground is very uneven, it shouldn't be too hard. To use a transit, you could setup in the middle of your square, set zero due "north"(assumed), then turn 45° increments, and pull 1/2 the above measurement, but that complicates things, and doesn't make measuring much easier.

Alternately, you could setup on one corner, sight a corner on line, and use 0°, 45°, and 90°, and pulling the appropriate distances to setup the square. That would be a good check after using tapes only. Setup the square using tapes, then setup the transit and wind angles. You don't really have to measure then. Your angles should hit the points you taped to.

paperfist

#### paperfist

##### Diamond Member
Your cross pull would be 19' 9-5/8". Unless the ground is very uneven, it shouldn't be too hard. To use a transit, you could setup in the middle of your square, set zero due "north"(assumed), then turn 45° increments, and pull 1/2 the above measurement, but that complicates things, and doesn't make measuring much easier.

Alternately, you could setup on one corner, sight a corner on line, and use 0°, 45°, and 90°, and pulling the appropriate distances to setup the square. That would be a good check after using tapes only. Setup the square using tapes, then setup the transit and wind angles. You don't really have to measure then. Your angles should hit the points you taped to.

Thanks for the cross pull #. I'll try the last method as I have 1 post set.

I was toying with the idea of ripping some plywood into 4 pieces and making a giant L square before I rented the transit .

#### Greenman

##### Lifer
This seems like a very geometric problem.

http://www.mathopenref.com/constsquare.html

Instead of a ruler and compass I'm thinking strings and stakes.
Bingo!
Batter boards are what he needs. Establish where you want one side, go a few feet past and set two stakes about 2' apart, tack a third stake across the top. Do that at the other side as well. From there it's easy to roughly lay out the batter boards on all four corners. Then you pull string lines across. First the front, then the back, the two sides you get by measuring across the diagonal.

#### Greenman

##### Lifer
Your cross pull would be 19' 9-5/8". Unless the ground is very uneven, it shouldn't be too hard. To use a transit, you could setup in the middle of your square, set zero due "north"(assumed), then turn 45° increments, and pull 1/2 the above measurement, but that complicates things, and doesn't make measuring much easier.

Alternately, you could setup on one corner, sight a corner on line, and use 0°, 45°, and 90°, and pulling the appropriate distances to setup the square. That would be a good check after using tapes only. Setup the square using tapes, then setup the transit and wind angles. You don't really have to measure then. Your angles should hit the points you taped to.
I came up with 19' 9-9/16. Assuming 14' to the outside of the post. I'm guessing you rounded up because he'll never get them that perfect.

I have a PDF of the complete layout if you want it.

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paperfist

#### lxskllr

##### No Lifer
I came up with 19' 9-9/16. Assuming 14' to the outside of the post. I'm guessing you rounded up because he'll never get them that perfect.
I figured it using decimal feet(cause next to metric it's the sanest measuring system :^P ), then did a trial/error conversion to imperial. I got within 1/8", and figured close enough :^D

#### Greenman

##### Lifer
I figured it using decimal feet(cause next to metric it's the sanest measuring system :^P ), then did a trial/error conversion to imperial. I got within 1/8", and figured close enough :^D
I cheated and drew it out with a cad program and measured it. The software is accurate to six decimals then rounds to the nearest 1/16".

#### lxskllr

##### No Lifer
I use decimal feet exclusively at work, and do the same at home. It makes everything easier when doing math. I'd prefer metric cause the smallest marked graduation(1mm) is close enough for all but the most demanding construction, as opposed to decimal feet which is .01', or ~1/8". I don't understand the resistance to metric. It's easy to use, and if you have the standard number of fingers, easy to do math with. Bonus is you're compatible with the rest of the world.

#### Greenman

##### Lifer
It's all about what you're used to. After 40+ years of using fractions at work, looking at a metric tape measure gives me a headache.
When I'm drawing it doesn't mater what system I use. I'm comfortable in feet and inches, but the software will work just as well with cubits or light years. The conversion to whatever system I need is just a key press away.

#### paperfist

##### Diamond Member
This seems like a very geometric problem.

http://www.mathopenref.com/constsquare.html

Instead of a ruler and compass I'm thinking strings and stakes.

I know, I get it simple math, 14' this way, 90 over 14' that way, 90 again 14' this way and repeat one last time. Measure on the diagonals for square.

I just want something easy like a laser so I don't have to drive stakes for batter boards into soil filled with rocks, uneven terrain, buying more materials, dealing with a tape that doesn't cooperate. lol

#### paperfist

##### Diamond Member
I cheated and drew it out with a cad program and measured it. The software is accurate to six decimals then rounds to the nearest 1/16".

Can you layout the hip roof for me w/1’ overhang?

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paperfist

#### paperfist

##### Diamond Member

It's okay I appreciate the offer, but I'm probably just going to get trusses made. If I can't handle the math on a square then the math on a hip roof will send me to the white room.

If I change the square to 14'6" then the diagonal is 20' 6 1/16"?

#### lxskllr

##### No Lifer
If I change the square to 14'6" then the diagonal is 20' 6 1/16"?
correct
(14.5^2+14.5^2)sqrt=20.5061

so that gives us 20'6" with some crap left over. The way I handle it without cheating is trial/error math til I get close enough. In this case I'd do (1/16)/12=.00521. Close enough to your .0061 remainder.

There's probably some better way of handling it, but that's what I do. I've spent 30 years using decimal feet, and I'm comfortable doing math with that. If you do a fair amount of projects around the house, you might want to consider an engineers tape with decimal graduations. I got a 25' power tape from homedepot for <\$20. Convert your fractions to decimal feet, and enjoy easy math. Of course if you have to talk to anyone else, you'll probably get a blank look :^D

paperfist

#### Greenman

##### Lifer
Or just get a fractional calculator app for your phone. It's worth the two bucks.

#### paperfist

##### Diamond Member
correct
(14.5^2+14.5^2)sqrt=20.5061

so that gives us 20'6" with some crap left over. The way I handle it without cheating is trial/error math til I get close enough. In this case I'd do (1/16)/12=.00521. Close enough to your .0061 remainder.

There's probably some better way of handling it, but that's what I do. I've spent 30 years using decimal feet, and I'm comfortable doing math with that. If you do a fair amount of projects around the house, you might want to consider an engineers tape with decimal graduations. I got a 25' power tape from homedepot for <\$20. Convert your fractions to decimal feet, and enjoy easy math. Of course if you have to talk to anyone else, you'll probably get a blank look :^D

I’ll have to pick one of those tapes up tomorrow, didn’t know they existed. I’ve always liked to use the decimal measurements but honestly didn’t know that was an acceptable practice. I don’t think I’ve ever worked with anyone who didn’t use fractions.

I remember working for a plumber and when he got new apprentices he’d put them through the wringer. Whadda mean you don’t know what 1/8 is? Did you cut this pipe with your eyes closed? I said 8’ 3/4” not 8’ 1/4”! No lunch for you!

So guys what’s the acceptable range off on the diagonal? I’m off by 2”...

EDIT: I think I know why I'm off that much. I was subtracting 5.5" for 2 posts because I'm measuring from inside post to inside post, but the actual depth of a 6x6 on the diagonal is 8" so I should be subtracting 16" from the 246 1/16" measurement.

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#### lxskllr

##### No Lifer
Decimal feet are used by surveyors, and in highway construction. Architectural stuff is in imperial. Carpenters and the home building trades likely have no idea what decimal measure is, and will be confused if you talk to them in those dimensions. For your own use, you can do what you want of course. The power tape I got is DeWalt. Quality seems decent, but I haven't used it long enough. Always got lufkin in the past, but they're getting hard to find locally.

There's no such thing as a perfect measurement. Every measurement is made good enough for the task at hand. I'm not a carpenter, but 2" sounds like too much to me. In any case, it's best to start with better measurements than you need for the project. That leaves room for future error without badly affecting the outcome. If you start out wrong, it probably won't get better unless you get lucky, and leaves uncertainty in the fitment. I wouldn't want my error any worse than 1/4" starting my foundation.

paperfist

#### paperfist

##### Diamond Member
Decimal feet are used by surveyors, and in highway construction. Architectural stuff is in imperial. Carpenters and the home building trades likely have no idea what decimal measure is, and will be confused if you talk to them in those dimensions. For your own use, you can do what you want of course. The power tape I got is DeWalt. Quality seems decent, but I haven't used it long enough. Always got lufkin in the past, but they're getting hard to find locally.

There's no such thing as a perfect measurement. Every measurement is made good enough for the task at hand. I'm not a carpenter, but 2" sounds like too much to me. In any case, it's best to start with better measurements than you need for the project. That leaves room for future error without badly affecting the outcome. If you start out wrong, it probably won't get better unless you get lucky, and leaves uncertainty in the fitment. I wouldn't want my error any worse than 1/4" starting my foundation.

Interesting to know, I guess that's why all the carpenters I hang around are stuck on fractions I'll have to chat up my engineer neighbor tomorrow and see if I can slip him up.

It's 'just' for a gazebo. I edited my post above, I think my mistake was I was subtracting 5.5" (x2=11") from the diagonal measurement since I was going from inside to inside post, but a 6x6 is 8" at its depth so I should have been subtracting 16".

#### Greenman

##### Lifer
2" out of square will screw up the hip roof. If it was a gable end you could get away with it.
Inside the posts should be 18' 6-1/16". That's assuming 14' outside dimensions.

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paperfist

#### Greenman

##### Lifer
The diagonal dimension on a 6x6 (5 -1/2 actual) is 7-3/4".

paperfist

#### paperfist

##### Diamond Member
2" out of square will screw up the hip roof. If it was a gable end you could get away with it.
Inside the posts should be 18' 6-1/16". That's assuming 14' outside dimensions.

Awesome thanks! So just curious, on the diagonal since I'm 14' corner to corner are you reducing the 14' figure by 7-3/4" (err 15-1/2") to get that 18' 6-1/16" diagonal measurement for the inside of the 6x6 posts? Or would you use the 5-1/2" measurement of the 6x6?

The diagonal dimension on a 6x6 (5 -1/2 actual) is 7-3/4".

These things weigh a ton they are so swelled with treatment. I measured in the dark last night but it was 8". I'll check them again. I left one in the sun and it twisted so much after drying that I have to toss it

#### Greenman

##### Lifer
Awesome thanks! So just curious, on the diagonal since I'm 14' corner to corner are you reducing the 14' figure by 7-3/4" (err 15-1/2") to get that 18' 6-1/16" diagonal measurement for the inside of the 6x6 posts? Or would you use the 5-1/2" measurement of the 6x6?
I didn't do any math, I drew it in a cad program and measured it.
I layout everything I build this way. Often the architectural and engineering plans are different by several inches, and the engineer never accounts for HVAC ducts or plumbing penetrations. So I have to make room for them without affecting critical structural elements.
I also build a lot of raked walls, and it's an easy way to get all of the stud lengths without having to lay it out on the floor. Saves many hours of time and everything fits perfectly. The only trick to it is figuring out where to gather up the accumulated errors. Lumber varies, floors aren't perfectly level, existing walls are out of plumb, all of those things affect the measurements, so you have to decide where and how to account for those minor changes.
It's way easier to do all the thinking while sitting in a comfortable chair in an air conditioned office than doing it out in the sun and finding an error after it's built. I hate that, it's expensive and demoralizing. No one wants to take apart work they just finished.