New Foundation cost for ADU

3 Replies

I am trying to put together a cost for ADU in backyard in Fremont , CA . It is 20x40 = 800sqft area on a flat land. Can someone please let me know roughly how much it will cost me to add the foundation. I would like to know the cost for slab or perimeter foundation.

I got a 50k quote from someone on phone  for slab , which sounds too high for a 800 sq ft single story. on a flat piece of land

@Vipul Parikh

That’s seems kind of high. I’ve recently completed a few similar projects. Do you have piers? Do you have any structural details? Wondering if it is a standard T footing foundation with slab or raised floor?