Author Topic: Footing Requirement  (Read 1098 times)

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Offline Bob S.

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Footing Requirement
« on: August 08, 2017, 02:22:57 PM »
I need to put-in footings for a patio cover. The roof is a gable design built with 6/12 trusses 22' wide with a 18" overhang on each side. And the roof extends out 12' from the house. I plan on supporting the back side with the house and the front side with two post 22' apart the snow load is only 25#, and the frost level is 24" here in Nampa, Idaho but I would like to over build it. Will 4X4 posts work or should I use 6X6's?  I do not plan on building it in the near future but I am expanding the patio and I want to put in the footings now.
   Will the standard building codes cover this or do I need to hire a engineer?   
Any help you guy's can give me will be appreciated; Bob 

Offline MushCreek

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Re: Footing Requirement
« Reply #1 on: August 09, 2017, 11:40:30 AM »
22' is awfully far apart for posts. In FL (with no snow load), we had to put a double 2X equal in inches to the span in feet. In other words, for an 8' span, you would have to have a double 2X8. For a 12' span, a double 2X12, etc.
Jay

I'm not poor- I'm financially underpowered.

Offline icanreachit

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Re: Footing Requirement
« Reply #2 on: August 09, 2017, 12:34:07 PM »
Agreeing with MushCreek on this one - Much cheaper to run a middle beam and reduce your span to 11'. The post sizing will also depend on your spacing. You could probably do something like this with existing tables. Go top down though instead of bottom up:

1 or 2 stories? What's the resulting loading? Then what's your beam size, and finally what spacing do you need to support the beam. Ie, you could have a 3x12 beam and space much further, or a 3x10 beam and space much closer. Alternatively, you could do a stemwall and then you wouldn't need a beam.

Offline Bob S.

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Re: Footing Requirement
« Reply #3 on: August 09, 2017, 02:02:01 PM »
the 22' will be spanned by trusses. I will use a 11' LVL on both sides out from the house to the post. Thanks for the input, Bob

Offline Don_P

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Re: Footing Requirement
« Reply #4 on: August 10, 2017, 01:58:32 AM »
The beam will support 11' of truss + 1.5' of overhang X 12' of beam span X (25#+10# dead load) The post will support half of that + gable overhang ( the house will support the other half of the beam, check that foundation and support column)

Columns typically fail by buckling of a slender column, slenderness is largely a factor of height in proportion to the least dimension of width. slenderness buckling gives over to crushing as the control when the post is 1" thick in least dimension per foot of height... an 8x8 post 8' tall is checked for compression parallel to grain, it isn't going to buckle before it crushes. 4x4's are best for supporting mailboxes and fences, they are also ugly and rarely straight.   IMO :D

Offline chico_513

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Re: Footing Requirement
« Reply #5 on: September 02, 2017, 07:17:20 AM »
The question pertains to footing size - the allowable loads are based on soil type....1500psf for clay/sandy clay, 2000psf for sand/silty sand, 3000psf for sandy gravel/gravel....depth needs to be below frost line

Offline Don_P

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Re: Footing Requirement
« Reply #6 on: September 02, 2017, 02:47:47 PM »
Welcome chico  w*
Correct you are. One of the first things I like to ask a new guy on the job to do is build a set of sawhorses, I've learned a lot of ways to do them from that. The rest of the particulars are there, Bob and I went to a pm but I forgot to post back here. Feel free to walk us through the design.

 

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