30' x 50' pier and beam design help

[cilo]

  Love the site, long time lurker, lots of great people / ideas and projects floating around.  So figured I would finally post.

  Recently picked up a .5 acre lot in the TX hillcountry and working on getting things rolling, decided on a pier and beam design rather then traditional slab.  Plan on starting early next year just want to finalize designs and what not before.

  I planned on using 8" sonotubes possibly 5 gallon buckets on roughly 7ft - 7.5 ft centers.  3x  pressure treated 2x12's put together for the beams, would need 5 of these 50ft long  then on top of that 2 16ft 2x12's going 30 ft on 16" centers, then decking it.  Either way my basic question is will this work?  Is this overkill? Or is this insufficient?  Here is a rough drawing I came up with.  Any comments or suggestions would be greatly appreciated.  Thanks in advance.

-Andrew

[rocking23nf]

I think 2x12 is overkill. I built a 12x12 with triple 2x10 and the inspector said i could span it 10 1/2 feet and have a 1 1/2 foot overhang.

And a 12 foot 3 2x10 was heavy enough, i can only imagine what a 50 foot would weight.

Plus the extra cost for the wood.

you can probably even get away with 2x8 but you would have to check the span table for that.

[MountainDon]

Q: Is this a one story, 1  1/2, or what??

Q: Are you in a code compliance area?

Q: Even though I built a pier/beam cabin, why did you discard the idea of a slab on grade with a perimeter footing?

[cilo]

Q: Is this a one story, 1  1/2, or what??

1 story, 1500 sq ft, 10 ft walls, engineered trusses, wrap around porch.

Q: Are you in a code compliance area?

No.  But would like to build to code.  My only fear is building a foundation that will have "play" in it per say as you walk or sag over time.

Q: Even though I built a pier/beam cabin, why did you discard the idea of a slab on grade with a perimeter footing

I discarded the idea mainly due to costs and terrain.  I'm a carpenter / framer by trade and have never built a pier and beam foundation, and since it will be my home and not a customers I figured I'd try it.  Also like the idea of being slightly elevated , not worrying about foundation cracking , and being able to fix plumbing if necessary.

[n74tg]

Cilo:

My house is 30 x 57, so very similar dimensions to yours.  I used two beams made from tripled 2x10's (not 2x12), so my floor joist span is 10 ft.  The beams have worked out great.  They are supported about every 10 feet of length on concrete block columns.  I used 2x10 floor joists on 24" centers except where ceramic tile will be installed.  There I went to 16" centers on the floor joists.  

Everything is very solid and I've been quite happy with it.  

I have a blog about the building of the house (address below).  If you want to read about the beams and floor joist install go to the archive section around June, 2008.

Good luck.

P.S.  I concur with the other posters; you don't need 2x12's for beams or floor joists.  

[cilo]

Thanks for the replies and suggestions, and nice blog n74tg, lots of good stuff in there.  So should I just go with 2x10's for both the beams and joists? Or 2x12 beams and 2x10 joists.  Just concerned about going with a smaller wood size and a year from now wishing I didn't and it would have only been a difference of $500-1k which is nothing really.  Basically I'm saying that I am ok with overkill and being overbuilt, but how much is too much.

[John Raabe]

Your foundation beams need to be carefully speced out for the loads coming down from the roof (snow loads) upper level or loft loads, and then the main floor. These loads accumulate and must be carried by your foundation girder over a certain span between the piers. On my plans I trace those loads down and then use laminated 2xs or a glulam beam sized for that load.

There are no "rules of thumb" for foundation post and pier girders. You need to do a load trace where you will get a total load per lineal foot. Then you can use a  beam program and play with pier spacing and beam sizes. You may need some help from a designer or engineer for this.

In this way post and pier is not as simple as a concrete perimeter wall that can take just about any load without complaint. You just size the footer based on the number of stories.

[Dallas2build]

I'm very interested in your project as I plan to build a cabin very soon close to those same dimensions.  Please keep us updated to your progress.  I'm guessing snow loads won't be a real problem for you in the hill country.