Hey all. I am going to build a 16x24 cabin. I was thinking of doing a concrete pier foundation but in weighing out my options it would be easier and just a little cheaper to do a post foundation. Im thinking of doing 6x6 pt posts sunk down 5 feet (Im in N. MN) and using 4x8x16 concrete blocks for footers. Im going to follow the 16x28 plans and do 12 holes 6'6" apart. I may insulate the posts as well. Does anyone see a problem with this set up? I can get the posts for about $18 a piece. I will rent the bobcat and attachment ($220 a day). Can I backfill with the dirt I excavate or MUST i do a gravel/dirt mix? This process will save me from having to get rain barrels for water, a mixer, the crete, and tubes. Ill dig the holes, tamp them down, set the blocks, tamp again, set the posts, level secure and backfill. My first time doing this so Im sorry if this question is a no brainer. Thanks all Russ
If you bury your pt posts you will not be able to replace them easily if needed. I would use piers of concrete or block filled with concrete.
no you are right, like everyone else I keep going back and forth. I think I will use tubes. Extra work will furnish extra results. Can I use 8" tubes or do I have to use 10" or 12"? Sonotube instructions tell you not to use 8" unless you use a bell footing. Could I use 8" if I used a concrete block footing? Thanks.
I haven't had much experience so take my opinion with a grain of salt.
If water is a problem like you say you might be better off digging a footer with rebar sticking out and then use concrete blocks to come out of the ground. Once your piers are built you can add rebar in the holes and and fill with cement. It will take less than using the tubes.
Here is how I did mine with forms. If you have a clean hole after you dig it you can just pour the Portland cement in without forms.
(http://lh5.ggpht.com/_3mo56Lh1Uqo/SsZDUByq7gI/AAAAAAAAAqw/WyvgGuUAXAk/s400/DSCF1657.JPG) (http://picasaweb.google.com/lh/photo/le85FgevST1wmW_rJ8ItKg?authkey=Gv1sRgCOzctfmS3tHr4wE&feat=embedwebsite)
(http://lh5.ggpht.com/_3mo56Lh1Uqo/SsZDGdAFQsI/AAAAAAAAAqU/JTbn_5mIVog/s400/DSCF1660.JPG) (http://picasaweb.google.com/lh/photo/weUpfBaNn8udySYvho4Few?authkey=Gv1sRgCOzctfmS3tHr4wE&feat=embedwebsite)
Don't know if this will work for you but it would save on the amount of cement. We used little water mixing the Portland cement. We used more water to clean the mixer than anything else. In my area you have to use 5,000psi cement on all footers and piers.
got ya. Thanks for the info and pics. Ive decided Im going to do the tubes. Im going to do 8" tubes and my buddy has a mixer and generator I can use. Im going to use 5000psi as well. Im going to do basically what Johns 16X28 says to do. 6 on each side.
For my money 5000 psi concrete is overkill. Are you planning on mixing from scratch (sand, gravel, cement) or using bagged mix?
5000 psi Quikrete costs about 1/3 more than their regular which is 4000 psi when mixed according to specs. And that is the key. Mix with the least amount of water to get a workable concrete. Many DIY'ers use too much water and too much water is what makes poor concrete. One of the things anyways.
Another key to strong concrete is using enough rebar and curing it. If the concrete dries out (water evaporates or is sucked away in dry ground) before it cures (chemical reaction that needs moisture) it makes for lousy concrete.
My 2 cents.
Don I am lookine to use the pre mixed bag crete.
Not allowed to use premixed here. Has to be Portland cement with the gravel in it mixed on site.
Don't ask me why. I don't know.
We did sono tubes and recently found out that we won't get okay'd if we wanted to get inspected as part of the energy rebate program. Wish we would have done a monolithic slab. Just our 2 cents.
Just one other thing to consider...
The 6x6 wood piers are easy to add the needed bracing to. With concrete piers, it's tougher to attach the bracing.