I purchased 15 acres of ground in NE Tennessee and plan to build a 12x18 cabin with a pier style foundation. Can anyone give me some advice on the placement and spacing of the piers, beam spacing, and floor joist spacing. I'm new at this, so there is no such thing as too much information. Thanks!
The discussion over at http://countryplans.com/smf/index.php?topic=12772.msg167527#msg167527 seems pretty spot on for your application.
In general, "advice" on how to build is good, and this place is full of it, but there is no replacement to going and looking at the codes. You can probably find the TN codes online somewhere. Most are based on the IRC which is available here: http://publicecodes.cyberregs.com/icod/irc/2012/index.htm
For comparison, the NY codes are here: http://publicecodes.cyberregs.com/st/ny/st/b400v10/index.htm
Mountain Don's done some of the work for the other fellow with a 12 x 18, but you can go look for yourself at the code tables he references here:
http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_5_sec002.htm
Good luck on your build
(disclaimer: I didn't do a very good job on my piers and beam sizing for my 10 x 10, but I know better now. And my cabin will have continuous wall foundation)
Here is an overview of the pier foundation options: http://countryplans.com/foundation/index.html
The specific beam and post layout will depend on the size of cabin you will build. A 12' wide cabin could use the 12' wide pier foundation plan in the Little House plans kit (http://www.countryplans.com/jshow.com//y2k/listings/29.html).
Check with your code jurisdiction to see if they have restrictions on pier foundations and visit job sites to see what builders in your area are doing. Also, you need to have solid well drained soils or you can have settlement issues. You can have these problems with a concrete perimeter foundation too but that foundation should have rebar in the footing that will help it to span small soft spots. Remember there are some sites that shouldn't have buildings on them - usually wet sites that are lower than the surrounding land.
In some areas even well built pier foundations are viewed as reducing resale value.
QuoteR404.1.9.3 Masonry piers supporting braced wall panels.
Masonry piers supporting braced wall panels shall be designed in accordance with accepted engineering practice.
Can you think of anywhere where a non compliant foundation would increase or even preserve the value of an otherwise well built home? There are quite a few places where it stands a good chance of stopping a sale or preventing insurance. This is a foundation type that requires the services of an engineer.
Yes, there are many code areas that will require engineering on a foundation for a full sized house. Engineered pier foundations can sometimes still be cost effective and long lasting.
More to the point, however, small cabins and utility buildings are often exempt from code in many parts of the country. This is what K9Daddy was asking about, I expect. Thus the advice to check with the jurisdiction.
Many... 49 states have adopted the IRC, TN has adopted it statewide. The honest part of the discussion is over, that takes care of it right there. Sure we can look for an ignorant inspector but is that really how we want to advise people to act... running red lights as long as the cop is busy with his donuts? Sure you'll make it 99 times out of 100 but it isn't very smart. This foundation requires engineering by law. Each person is free to act as they see fit. If someone is comfortable building this in spite of the law (laws of physics as well) that is fine but we sure don't want to fool someone into thinking this is accepted construction practice, it is far from it.
The exemption is never for a habitable structure that I've seen in any code. I'd be interested in seeing it if you have a cite. The exemption is for small, low, utility and storage buildings... a Lowes shed. And actually although exempt from foundation requirements, they are required to be anchored here, we've had too much of that stuff land on someone else's car. Portions of NE TN are in the same special wind region that we are in.