Foundation thickness

[JCBigler]

Hello all,

I am looking into the costs of building a small studio to work in.

How deep does the foundation need to be? Also is it normal to have it reinforced with rebar in the concrete?

I'm looking at a slab that is about 720 sq. ft. (20*36). We live out in the country and isoloation to and from others around us isn't really a huge issue, except mabey the occasional piece of farm equipment.

I'm not looking for anything really fancy, just somewhere where I can go to record and edit.

[cadesignr]

How deep does the foundation need to be? Also is it normal to have it reinforced with rebar in the concrete?

That depends on the load it carries. No one can tell you that simply because they haven't got a clue to what you are building, what its made of, the soil conditions, etc etc. PLUS, every state, county, city has thier own codes that you MUST comply with, although it usualy is based on the Uniform building code.
Since you are building from the ground up, you NEED a permit. To get a permit, you have to apply for it at the Building inspection Department. Most likely, you will have to submit a set of plans to prove to them that you are COMPLYING with the local codes. Sometimes, depending on your location, for a simple residential structure or addition, they simply give you a typical detail sheet, but this by no means is permission to build it to those specs or tells you the codes. It is up to you to submit a plan that shows you are complying. Once your permit is obtained, you will ultimately have every step inspected. This is where you can run into trouble if your inspector finds something different than your plan shows. But if this building is NOT typical, or the property has some wierd conditions, such as its in a flood plane, or has wierd easments, or any number of things that tell them your plan doesn't meet certain codes, they will ask you to show why you are not complying BEFORE issuing a permit. This is what keeps people from building things that kill people.
fitZ

[JCBigler]

So, where do I go to find out how thick the foundation needs to be? And do I have to have finished plans for the building before I can figure out what the foundation needs to be?

[knightfly]

Generally no - in a given area and soil type, there will be (for residential purposes, anyway) two different specs for footing width and depth - one for 1-story buildings, and a heavier one for 2-story. There may also be an even heavier spec for 3-story, if that's even allowed.

The best place to find out about this is to call your local building codes office - if you're out of town, it will probably be your county building permit office. If all the soil in your area is the same type, they will probably already know how wide and deep your footings will have to be - this is typically 12" wide and 6" thick with a 6" stemwall for single story buildings on decent soil - if it's clay, they may want 15" by 7-1/2" footers because clay has lower compressive strength than most soils.

If you're doing a monolithic slab, you would just dig a 12" wide by 6" deeper than grade trench, fix your rebar where required (usually at least 3 runs for a monolith, more for a stemwall) and either lay steel mesh or order the concrete with "fibermesh" added ( a few $ extra, takes the place of the steel mesh but NOT the rebar) - most areas now require you to embed 20 feet of rebar in a new slab and bond connectors to it which stick out of the slab and are used for a building ground point.

My local building department has a small booklet that give a few basic things to do, including how to draw a plot plan, how to draw elevations and plan drawings, foundations etc - you should ask your local guys if they have anything available like that, or maybe on the net if they have a site. My area has both, and it's pretty "one-horse" - you might get lucky.

Beyond that, most building depts won't always tell you the RIGHT way to do things, but they WILL tell you (by redlining your drawings) what you CAN'T do - if you can find a local contractor who's willing to talk without pay, he would be a good resource - in fact, a reasonable paid consultation wouldn't be money wasted here... Steve

[cadesignr]

Hello Justice, I hope I didn't sound negative. I tend to look at the problem using my own experience with things. I am definetely not an expert at this stuff, but I have delt with it enough to guess at a solution. Personally, I would just make a visit to the Building Inspection Department, or where ever you apply for permits in your city or county. Tell the clerk what your intention is and see what they say. At least, they will tell you what they require. They may even provide you with a typical detail sheet showing minimum requirements for footings and foundations, but I can't be sure. I know in my old location, in Sacramento California, the permit process for residential USED to be simple. But within the last 5 years has become a real pain in the butt. Building a simple shop building was such a hassle, and had so many restrictions just because I called it a shop, I gave up. Not to mention EXPENSIVE FEES. Now days, all paperwork and applications had to go through the assessment office, the fire department, the electrical inspection department, etc etc etc What a beauacratic nightmare. I'm all for permits, but it sure can be a difficult thing to go through. Anyway, check with them and maybe they can provide you with the information you need. If not, you may have to consult with an architect, or engineer, or contractor. All I do know is no one should give you the answer for foundation depth on a forum. Especially without knowing any particulars of your construction intent.
fitZ

[cadesignr]

HOLY COW Steve, you posted while I was typing the same thing.
fitZ

[knightfly]

Yeah, either the "great minds" thing, or we're BOTH "de-railed"...