20 x30 1 1/2 story loft

[deabob11]

Can i just extend the loft to cover the enitire 20x30 area without using any other types of support and take out the beams or are these beams needed for support?
2x12x20 jiosts
thanks for any help.

[John_M]

The beams that are needed to support the loft floor can be placed all the way across and create one large loft with no cathedral type ceiling in your structure.

Make sure the species of lumber you use is strong enough to span that distance.  You would want to use good quality (#1 grade or better) lumber here as well.

[deabob11]

  Thanks!
i have never built anything larger than a shed in my life and just want to make sure that the plan change was safe.
 
The local lumber yard is going to to sell me #2 2x12's that could span the 19'6" of the cabin.  Should i ask for a better grade of wood?  (These #2 2x12's were going to be used for both the main floor and the loft floor.)   Stock plans with no support in the center of the loft or main floor.

Another question
I was going to use a post and peir foundation and have had some trouble finding local codes on this type of foundation.   The frost line in this area is 30".  
My plan is to dig a hole that has an 18" diameter (i have heard it might have to be 24") and is at least 30" deep.   Then i was going to put 1- 2 bags of dry concrete in the bottom of the hole and get the posts set into place.  After that i was going to try and have concrete delivered to fill the holes, otherwise i will mix it by hand with lake water (i don't want to have to do this).

The soil is a clay/silt mix over limestone bedrock.  If I hit solid rock( one solid rock over the bottom of the entire hole), could I just put some gravel on the rock and set the post or would i have to chisil into the rock?
Thanks for any help.