How many piers?

[optionguru]

After 5 or 6 years and 3 different pieces of land I've finally decided to build a 16x32 on post and pier.  The question still seems to be can it safely be built on 2 carrying beams with a cantilever or should I go with 3?  I was thinking of doing 3 with 15 piers on 8' centers.  I have a backhoe and was going to use the precast 5' tall piers buried 4 1/2 feet.  I live in northern nh with a 4' frost depth.  Thought of using 12' walls to add height to the upstairs loft.  Any thoughts would be greatly appreciated.

[Don_P]

A backhoe does a better job making trenches, you'll spend less time and get a better job digging a full perimeter trench, if you do a center girder it is just another trench. Digging piers 8' apart and 4' deep you pretty much already have a trench. Really every time I've tried it would have been quicker to just rip a trench. At that point it is just a truckload of concrete to a code footing. Even if you do not put in a code foundation, the base is there and creating a good base to work from. In conversation with one engineer he suggested stacking ICF forms in the corners making stable wall corners with piers at necessary spacing between those wide corners.

Just a thought and I'll sit on my hands, y'all can speak freely.

[Squirl]

8 feet is a very large span between piers.  With your snow load you will probably need very large footings to handle the weight.  Your beams will have to be quite substantial ($$$) to span that distance.  I don't know if it is one story or two.  A second floor is double the weight and it can get complicated on how the weight is distributed. 

You are ahead of the game with a backhoe.  As long as you have that to do the digging, I would dig a trench and put in a full foundation.  Concrete is cheaper than wood.  I would, at minimum, put in more piers.  The built up beams to span 8 ft will be expensive. An extra pier in between cutting the span to 4 ft, would probably cut the size of the beam to 1/4 the size and cost.

[optionguru]

I've built a number of basic buildings with piers or telephone poles in the ground.  I' ve never poured a full foundation, is there a do it yourself way to do it or do I have to hire a company with forms to do it?  The back hoe digs about a 2 1/2 foot wide trench, that would be a lot of concrete to fill the hole without forms.  I do have water and sewer on the building site so that could be a consideration as well.

[flyingvan]

Optionguru---every now and then I post my method for fabric formed foundations....Just an option to consider but it sure worked (twice) for me, and only one day of help----I didn't want any cold joints so poured all the concrete at once and had friends help push it in to the forms
http://countryplans.com/smf/index.php?topic=11812.msg151774#msg151774
http://countryplans.com/smf/index.php?topic=11821.msg151922#msg151922
  I like it because there are no cold joints under ground where the footing meets the stemwall, just a bulbous mass.  If you encounter a BIG (Too big to move, blast, cut, etc) you just drill into it and epoxy rebar in, let it poke through your fabric, and continue on.

[JRR]

............... The back hoe digs about a 2 1/2 foot wide trench, that would be a lot of concrete to fill the hole without forms..............

Not really.  The minimum width is usually 1-1/2', or so.  So what's an extra foot width of footing? ... except more footing.  How bad can that be?  Ready mix concrete is not that expensive.... even with the steel reinforcement that I hope you will add.  Quite frankly, I always have my footings approx that width ... well reinforced ... 8" thickness minimum.

[optionguru]

My backhoe bucket and teeth are about 20" wide.  The issue with the extra foot of thickness with a 4 1/2 foot tall pour is about 2000 extra in concrete.  Trying to save money where possible.  The fabric idea looks interesting.  Thanks again for all the ideas.

[Squirl]

Footings are usually formed with 2x8s.  If you are using any 2x8s in your build, these can usually be reused.  Flying van did a nice job with the fabric form.  A single pour can be intimidating and nerve racking for a DIY.  I was worried I wouldn't be able to reuse the forms for the house.  I and many others have done block foundations. Cheap, one block at a time, and not brain surgery.  There are two different methods. 

First is the old fashioned mortar.
[embed=425,349]http://www.youtube.com/watch?v=yc9TNxnjtLo[/embed]

And dry stack.
[embed=425,349]http://www.youtube.com/watch?v=fNB9x8dq9_0[/embed]

There are many first time builders here on the forum that have done one.

[JRR]

............  The issue with the extra foot of thickness with a 4 1/2 foot tall pour is about 2000 extra in concrete. .......

I did not realize you intended to fill the entire ditch with concrete.  Folks ususally pour only a 8" thick, or so, footing .... and then the wall, 8" - 12" thick, is poured of formed concrete or laid up in block.

[optionguru]

I've never done forms before so I was trying to avoid it.  I've used the piers before so I guess you just naturally try to stick with what you know.

[flyingvan]

  One of the reasons I like to build is to step out of my comfort zone---(hence the curved roofs, native stone tile, etc) but there are probably as many different reasons to be an owner/builder as there are owner/builders...

[MountainDon]

Thought of using 12' walls to add height to the upstairs loft.  Any thoughts would be greatly appreciated.

That is another item that needs some thought. If there's an 8 foot main floor ceiling that extra 4 feet of stud length has its problems if your intent is to sit standard rafters on the tops of the side walls. With any sort of a snow load that will create some large outward horizontal forces that will want to bend the stud tops outward (if as I assume there will not be any rafter ties at the actual stud top.).