contractor input on concrete footings for cabin

[timberland]

I am building a 24x28 cabin on an 8" block crawlspace. I am planning on 16"x16" concrete footings. The cabin will have a covered porch on the long side. The frost depth is 36". What should I plan to do for footings for the support posts for the porch? should they match the foundation footings, 16"x16"x16"?

I know to be safe someone will say pour everything 40" deep, but we built houses like this in the past on these footings. any movement from frost wasn't noticeable, but they didn't have the porch.

anybody with advice or experience with this construction?

 

[ben h]

I'd pour a wider footing and about 10-12" thick as opposed to 16". For the deck piers, I'd look at the "bigfoot" system. https://www.bigfootsystems.com/include/bigfoot-footing-forms.htm
Where is this property at? For reference, I am a structural engineer.

 

[timberland]

northwestern WI, straight east of Minneapolis

 

[def90]

Even though your porch/deck will be on posts you may want to consider just pouring a complete footing around the whole porch in case down the road you want to make it a fully enclosed and conditioned part of the structure. The tie in to the cabin footing also helps with any possible settling issues that the seperate posts may have over the rest of the cabin. Soil conditions and so on may also be an issue. This is something that should be brought up with the structural engineer.

 

[GSPHUNTER]

Best answer is, check local building code.

 

[stanginthe11s]

porches and decks do not require the same footings as a house as the static and dynamic loads are less. that being said a point that was mentioned is you may change ideas at a later time so having the large footing will allow you to do changes without worrying about it, of course that's assuming you over build the porch framing as well. hard to say without know your plans, but for ease and peace of mind just stick with the size you're already doing for the house. as for depth frost heave will affect the porch before the house so you might want to be well below that frost. a lot of variables to give proper answers, location-materials-techniques etc. all play a part in how you spec out any part of a structure.

 

[loganwayne]

as others have said do it to code. but ill also add most of our guys that we use for footings use a 24" bucket. so our footings are 24". All our footings are 12" think unless otherwise noted.

 

[GSPHUNTER]

My answer about checking local building code it your best bet. I live in an area that is prone to earthquakes. If I were to give you info about our requirements, it would be way more than what would be needed for the area you live in.

 

[DenverCountryBoy]

Footing width is determined by soil type, live and dead load, and local conditions.

Depth is frost line plus 6". The porch footing area will get colder than the area with heated space. Don't skimp on digging the footings to depth, especially with a temperature differential that could come back to bite you.

 

[Agross]

I would dig the ftgs deeper if anything than shallower. It’s the “foundation” for the whole thing. Gotta believe u get a lot of frost where yer building.