pier and beam foundation

Bobb · September 20, 2007, 11:04:46 PM

Hey all. I'm new at this so please redirect me if I'm in the wrong forum.
I need some advice on my plan for building a house using a pier and beam foundation.

Here it is: 18 holes dug around 36" deep and 12-15" wide. 3 rows of 6 piers with 8 foot spans between piers and 12 foot spans between rows. Very good soil with clay and rocks on a limestone bedrock shelf. 3 foot drop from high point to low point. Concrete footings in holes 15-20 inches thick with 1/2" rebar. Piers made of concrete poured into 8" sonotube. Girders 3, 2x12's nailed together. In piers install threaded rod through tube to use with 2x4 for bracing on girder. House will be around 42feet by 24feet, two story salt box.

What do you think?

glenn kangiser · September 20, 2007, 11:24:18 PM

Welcome, Bobb.
Sounds pretty substantial.

Were you working off of a plan? Sounds similar to John's, but longer.

September 21, 2007, 07:50:12 AM

Thanks Glenn,
No real plan, just stuff I've gleaned off the website and other books. I do have the 24x14 plan but this is much bigger obviously. I had an architect question my piers and was concerned with lateral motion but I think the braces and concrete piers should keep it stable. I would like to over build the foundation, maybe this is too much I don't know.

Bobb

TheWire · September 21, 2007, 08:03:10 AM

I'm assuming the lateral loads would be side forces primarily from wind. How far is your cabin sitting off the ground at the low end? If its close to the ground and secured to the columns, it should provide a good anchor for the rest of the building. That combined with bracing on the taller legs is going to provide a lot of stability.

Jerry

glenn kangiser · September 21, 2007, 09:06:32 AM

The all thread through the Sonotube a bit up from the ground on the tall piers to bolt diagonal bracing to sounds good. I'd use washers on both sides of the brace. Other than that, 36 inches in the ground seems like pretty good bracing.

September 21, 2007, 09:20:17 AM

I assume you were putting vertical rebar in the piers also :-?

PEG688 · September 21, 2007, 09:31:01 AM

QuoteHey all. I'm new at this so please redirect me if I'm in the wrong forum.
I need some advice on my plan for building a house using a pier and beam foundation.

Here it is: 18 holes dug around 36" deep and 12-15" wide. 3 rows of 6 piers with 8 foot spans between piers and 12 foot spans between rows. Very good soil with clay and rocks on a limestone bedrock shelf. 3 foot drop from high point to low point. Concrete footings in holes 15-20 inches thick with 1/2" rebar. Piers made of concrete poured into 8" sonotube. Girders 3, 2x12's nailed together. In piers install threaded rod through tube to use with 2x4 for bracing on girder. House will be around 42feet by 24feet, two story salt box.

What do you think?

Where are you located? Thats a lot of building for a pier foundation IMO.

glenn kangiser · September 21, 2007, 09:38:17 AM

That looks like a legitimate concern, PEG. I wonder how far it is to the limestone shelf.

I saw that the 20 wide 2 story had 8'6" spacing on piers option but I assume soil conditions would have to be very solid

Bobb · September 21, 2007, 02:19:05 PM

Great thoughts by all, thanks.
House will be about 18 inches from ground on low end and about 40 inches on highest. Yes, rebar in columns. I'm in southern Missouri, lots of rocks and clay. Limestone shelf is about 1-2' under deepest hole. Wind is a concern with the house being two story. I agree it would be a lot of house for a pier foundation, but I think the ground is very stable under the piers, at least I hope it is. Any other conserns come to mind?
Thanks,

Bobb

September 21, 2007, 03:16:51 PM

Okay more info. My holes are only about 30" deep, not 36. We drilled with an auger until we hit rock and could not dig any further even by hand.
Our well pump was to be put in the ground, but backhoe could not get through rock about 20 ' from home site. Also septic tank which is about 100' down hill from site, is only 4 1/2 ft down because of rock shelf. So, based on this I feel the site piers will be stable with no sinking. I guess I am a little nervous about the house being two story and on piers.

Bobb

PA-Builder · September 21, 2007, 08:08:00 PM

If there is any inspection required, you may want to run your plans by the local building inspector. You may also want to speak with your insurance company, since some don't like post/pier foundations. You're at the point where changing things is easy, don't screw up that big a house with an inadequate foundation.

MountainDon · September 21, 2007, 08:22:29 PM

QuoteIf there is any inspection required, you may want...

IF there is any permit/inspection required you Must run the plans through the appropriate department. No point guessing.

If there are not any permit/inspections, are there area neighbors? Most will be friendly and may have valuable insight into local conditions and information. You might even get lucky like I did and find one with some of the machinery that cuts out some of the manual labor or the need to rent it yourself.

Having a rock solid relatively shallow base can be both a blessing and a hindrance, depending what the task at hand is.

Bobb · September 22, 2007, 04:00:04 PM

No permits required in these parts. Yes, insurance could be an issue, I'll have to check on that.

I have a contractor friend overseeing what I do. He seems to think we're ok. He just doesn't want me mixing my own concrete.

Bobb