I am building an addition 24 X 40 to my existing cabin this fall. In the spring the ground is wet and is mainly clay. I was thinking about supporting the structure with pillars in 4 to 5 feet of concrete below the frost line with treated 6 x 6 posts to support the floor and building but I am not sure if that is a good idea or how many pillars I would need to support the structure. I am afraid of using a slab due to cracking and heaving. Any Ideas
You can space them at any spacing you would like up to a reasonable point (ex. 20' spacing is way too much). You will need to size the pier diameter and beams between them based on the decided span. Snow loading, wind load, earthquake load (if applicable), dead load, and live loads play a part in determining the beam size.
Slabs on grade can be insulated along the edges to protect from frost. Most areas have building codes that require it. If designed and built properly, a slab can remain solid for a very long time.
Last edited by AGWhitehouse; 07-12-2011 at 10:42 AM.