Tolerances / technique for squaring pier layout....

[NM_Shooter]

Just curious... In laying out / digging / setting piers, what sort of tolerances are acceptable for setting the piers "square"?

In the past, I usually set steel fenceposts in one line, at the corners of the structure.  Then triangulate the other corners based on the location of the first two posts. 

Since I have only built stemwall type structures in the past, I would then set the forms and measure cross corner to cross corner to get it square.  If I was within 1/2" I would call it good.  (Never could get the error to zero).  BTW... I think my house has worse tolerances than this.

Anyway, back to piers.  My plan is to complete two corner piers on the "long" side of the cabin to set a baseline reference.  Then once these are set, triangulate off of these to set the opposite two piers. 

Once the four corners are set, then stretch string pier to pier around the rim, and place intermediate piers as needed.  Obviously zero error is great, but what sort of tolerances should I be shooting for?

Is there a better way?

Thanks,

Frank

[Redoverfarm]

NM would batter boards not be acceptible for this. I usually install them first and use them constantly as I progress off the foundation.  If they tend to get in the way occassionally you can set nails at the locations, take the strings down and reinstall to the original location.  I am not sure what you are going to use for piers but you could square the batter board strings and then it would give you all four corners as well as the interm piers.  I imagine you are familar with the 3:4:5 theroy being that the measurement off the corner to a point of 3' then the other direction for 4' then that diagonal will be 5'. 

[MountainDon]

Using batter boards make it more likely that you can square the 4 corners up darn near perfect. It becomes much easier to fine tune the positions of the corners. I've done it to having the diagonal measurements within 1/8 inch with a steel tape, on a 24 ft x 24 ft building.  Like Redoverfarm mentioned, for some things they get in the way, but marking the boards and marking the string attachment points, using a nail or whatever, will allow moving one or more boards/strings and replacing them in the right spot.

The main thing IMO, with batter boards, is to make sure the pegs/posts you use to attach them to are secured so the don't shift if bumped.

Once the 4 corners are set satisfactorily the sides should fall into place.

[peternap]

Batter boards here too. Like Don. I've hit 1/8 but won't accept anything over 1/2.

This one was a touch under 1/8 because I fiddled with it an extra hour. Without sills to set on the subfloor, It had to be tight.

[MountainDon]

Just in case anyone is wondering about what batter boards are...

... set low to the ground...


... set higher, with bracing...



The above images taken from HERE. Follow link for accompanying description.

[ScottA]

I used batter boards like Dons picture shows. It turned out accurate to 1/4" for me.