Hello everyone.
In Florida, looking to build a house using Sonotube foundation.
Does anyone know how deep they have to go?
For example, can I use a 4' tube, bury 2' and leave the other 2' sticking up?
Read the foundation chapter of the code, a pier foundation is an engineer required foundation. But in the deep south especially there is no advantage to doing one. If you build a "prescriptive", that is, codebook foundation, you will only need to go 12" below finished grade. It will require a continuous perimeter footing and foundation but this will be in the same price range as a sonotube and girder foundation... and worlds stronger. Look at the crawlspace, permanent wood, or pier and curtain wall foundations in chapter 4 of the codebook for ideas.
The reason I was thinking sonotube is because the site is remote and there's a slim chance a pump truck gets in there, however with some help I could get 100 bags of concrete up there and some 5 gallon water jugs and a mixer and pour tubes.
I see that excuse pretty often but have never personally failed to get the mud to the site. I doubt you'll get the building department on board with it. Build a driveway now rather than later, then invite in a concrete truck.
There are a few reasons why I want tubes.
#1 is lower materials cost.
#2 is lower labor cost.
#3 is I have to build above grade and tubes accomplish that without a ton of materials use.
#4 is remote location and I don't want to cut in and gravel 1/4 mile of driveway right now just to accommodate a concrete truck.
#5 is that even if I decided to rent a pump truck with a huge extension hose and a suite of laborers to manage it all, there's a weigh station that essentially bisects our region in half and I'm on the 'wrong' end of it for ordering concrete. I'd have to order from a concrete supplier 2-3 hours away, which is even more $$$.
So, unless there's something specifically contra to the Florida Building Code, it's tubes.
If you are required to meet code, have inspections as is the norm when building with a building permit, a pier foundation needs to be approved on an individual basis. The IRC code as implemented there does not allow piers on a prescriptive basis. Piers would fall under the catch all of "approved or accepted engineering practice". That is not the exact wording but that is the gist of the code statement. That will be found in chapter 4 on Foundations.
An engineer might be able to design a pier foundation that could meet code. That would likely cost much more than a foundation as prescribed in the code.
Ugh.
That's bad news