foundation Question 20x30 single story

[astidham]

Hello all, i bought the 20x30 single story house plans.
I am going to build this house on a pier and beam foundation but i have 2 Questions before i start

1)IF i wanted to extend the length the house the plans say increase by 6', am i reading that right?

2)if i dig my footing holes 24"x24" to a deepth below the frost line and pour concrete to grade then set my post anchors would this pose a problem for my house? my soil is red clay(skiatook Oklahoma)

[dug]

I'm pretty sure you can increase length by any amount as long as pier spacing does not exceed what is specified in plans. Less spacing (between piers) is always O.K.
The top of the footer should be below the frost line. For example if frost depth is 24 in., you would need to dig 36 in. to pour a 1 ft thick footer. I think 24 in. should be wide enough for most any soil type, but I am not positive on that. Maybe I am reading your post wrong but you certainly don't want to pour the full 24 in. diameter to above grade, only the footer.

Lot's of rebar!

[astidham]

Thanks Dug,
I wasnt sure about the spacing because the current spacing is 7'6 between piers before adding length.

[Redoverfarm]

I'm pretty sure you can increase length by any amount as long as pier spacing does not exceed what is specified in plans. Less spacing (between piers) is always O.K.
The top of the footer should be below the frost line. For example if frost depth is 24 in., you would need to dig 36 in. to pour a 1 ft thick footer. I think 24 in. should be wide enough for most any soil type, but I am not positive on that. Maybe I am reading your post wrong but you certainly don't want to pour the full 24 in. diameter to above grade, only the footer.

Lot's of rebar!

I was always told and practice that the bottom of the footer is what is susceptable to frost/freeze  heave.  That is the portion that will be lifted in that freeze situation. The ground adjoining the outside of the footer will raise and lower but will not bother the bottom which is actually what you are wanting to prevent from this same process.  I guess you could pour the top below that frost /freeze level but you would be using extra labor/material which would not actually benefit the soundness of the foundation. 

[Don_P]

John beat me to it,

I'm pretty sure you can increase length by any amount as long as pier spacing does not exceed what is specified in plans. Less spacing (between piers) is always O.K.
The top of the footer should be below the frost line. For example if frost depth is 24 in., you would need to dig 36 in. to pour a 1 ft thick footer. I think 24 in. should be wide enough for most any soil type, but I am not positive on that. Maybe I am reading your post wrong but you certainly don't want to pour the full 24 in. diameter to above grade, only the footer.

Lot's of rebar!

The frost depth is the depth to the bottom of a footing "shall extend below the frost line". They may start at grade and extend down to frost depth. There is nothing wrong with going deeper but it is unneccesary.

[John Raabe]

Yes, the bottom of the footer should be at or below frost depth. The footer is normally poured with a 1/2" or 5/8" bar coming out of the middle. That will be tied to the rebar that will run up the center of your column out of the soil and then tied to the post on the bracket that will hold the beam.

See the Concrete tube or Block pier here: http://countryplans.com/foundation/index.html

[dug]

Oop's. don't want to cause anyone extra work. I thought that is how I read it in my reference book. Guess I got a little extra workout digging mine!

[astidham]

Thank you all.
if the weather ever clears up i will start the digging!

[Don_P]

There is reason to go deeper in some instances. A post frame building uses depth of embedment to provide a good deal of the lateral load resistance to the building.

[Redoverfarm]

Don when I was typing the reply to the post I had that in mind but didn't know how to represent that so I left it out.   You explain it much better than me anyway.

[poppy]

Don't forget to take pics.; we love the pics.