Post and Beam - Floor Overhang

[Freddy]

Hello, I am putting a 12 by 24 addon to a country home and am going to be using a post and beam foundation for it using 3 rows of 5 posts.  I am about to dig in the posts but have a question about the placement of the permiter posts.  I see some plans and pictures where the outside posts are inset from where the final outside wall will be, and others where the posts are directly under the outside walls.  I guess the advantage to them being directly under the outside walls is a straight down load path, insetting on the other hand lets you center the beam on the post instead of it being over to one edge and also letting the whole thing have a more finished look.

When searching the forum I read a post from John Raabe saying

"You can inset the support up to the depth of the joist or beam and as long as the line of force is 45º this is the same as being under the load."

Can anyone here help me out and let me know if one of the two ways is better or if it doesn't matter?

Thanks for your help

[dug]

If you build it using the guidelines you mentioned I don't think it will make any difference. I inset mine only because my piers were a larger diameter than the beam and I didn't want them to protrude beyond the outside edge. I guess it comes down to how you would like the finished look and weather or not you are going to skirt it.

[rocking23nf]

Beams and joists use a term called "cantilever", which is basically how much a beam/joist can overhang a support post/beam safely.  I dont have the chart in front of me, but on my 12 foot triple 2x12 beam, I think it was 18 inchs I could overhang the beam safely.

The benefit being, if you use a size wood that is only acceptable for a 10 foot span between posts, you could overhang the beam another foot or foot and a half and have an 11 1/2 foot beam, with your posts spaced 10 feet apart.

Im just putting in random numbers, none of those should be considered proper calculations or distance.